Killer T Cell-Mediated Apoptosis Pathway: Recognition, Effector Molecule Release, and Target Cell Death Mechanisms
Killer T Cell-Mediated Apoptosis Pathway: Recognition, Effector Molecule Release, and Target Cell Death Mechanisms
The killer T cell-mediated apoptosis pathway mainly refers to the process by which CD8⁺ cytotoxic T lymphocytes (CTLs) recognize abnormal target cells and induce target cell apoptosis through the perforin-granzyme axis, the Fas/FasL death receptor axis, and TNF-related signaling. This pathway is a core cytotoxic mechanism in antiviral immunity, antitumor immunity, transplant rejection, and autoimmune tissue injury.
Keywords: killer T cells; cytotoxic T cells; CD8⁺ T cells; CTL; apoptosis; perforin; granzyme B; FasL; Fas; caspase; immune synapse; tumor immunity; antiviral immunity
1、Basic Framework of the Pathway
1.1 Target Cell Recognition and CTL Activation
(1) Antigen presentation
Endogenous antigens in target cells are degraded by the proteasome to form antigenic peptides, which are then presented on the cell surface by MHC I molecules. CD8⁺ T cells recognize peptide-MHC I complexes through TCR, which is the core prerequisite for initiating cytotoxic responses. Virus-infected cells, tumor cells, and graft cells can all be recognized by CTLs through this mechanism.
(2) Co-stimulation and activation threshold
TCR recognition usually requires the cooperation of co-stimulatory signals, such as the interaction between CD28 and CD80/CD86. IL-2, IL-12, type I interferons, and IFN-γ can further enhance CTL differentiation, expansion, and expression of cytotoxic effector molecules. If antigen stimulation exists but co-stimulation is insufficient, T cells may enter a hyporesponsive state, showing infiltration without adequate killing.
(3) Inhibitory regulation
Inhibitory receptors such as PD-1, CTLA-4, TIM-3, and LAG-3 can raise the cytotoxic threshold of CTLs and reduce degranulation and cytokine release. In the tumor microenvironment or chronic infection, even when CD8⁺ T cell numbers increase, target cell apoptosis may remain insufficient due to exhaustion or inhibitory states.
1.2 Immune Synapse and Polarized Release
(1) Immune synapse formation
After CTLs recognize target cells, TCR, LFA-1, ICAM-1, and related signaling molecules form an immune synapse at the contact interface. This structure helps stabilize the contact between effector cells and target cells and limits the diffusion of cytotoxic molecules toward non-target cells.
(2) Granule polarization
Cytotoxic granules inside CTLs polarize toward the immune synapse. The microtubule-organizing center, actin rearrangement, and vesicle transport system jointly control directional granule release. This process determines whether the killing response has spatial precision.
(3) Degranulation readout
CD107a externalization is an important experimental indicator of cytotoxic granule release. If CD8⁺ T cells express GZMB and PRF1 but CD107a does not increase, it indicates that cytotoxic molecule reserves are present, but the granule release process may be insufficient.
2、Perforin-Granzyme-Mediated Apoptosis Pathway
2.1 Perforin-Mediated Granzyme Entry
(1) Role of PRF1
After being released by CTLs, perforin (PRF1) can form pores in the target cell membrane or endosomal membrane, allowing granzymes to enter the cytoplasm of target cells. Without effective PRF1 cooperation, even if granzymes are released, they may not sufficiently access intracellular substrates.
(2) Types of granzymes
Granzyme B (GZMB) is the most typical granzyme that induces target cell apoptosis and can directly activate the caspase cascade and mitochondrial apoptosis pathway. Granzyme A (GZMA) is more inclined toward non-caspase-dependent injury, ROS generation, and inflammatory cytotoxic responses.
(3) Pathway interpretation
Only when PRF1, GZMB, and CD107a increase simultaneously, accompanied by enhanced target cell apoptosis, can effective activation of the perforin-granzyme axis be more strongly supported. If only GZMB expression is increased while target cell death is not obvious, PRF1, degranulation, immune synapse formation, and the anti-apoptotic status of target cells should be further analyzed.
2.2 GZMB-Caspase Apoptosis Axis
(1) Activation of executioner caspases
After entering target cells, GZMB can directly cleave executioner caspases such as caspase-3 and caspase-7. Once executioner caspases are activated, target cells undergo PARP cleavage, DNA fragmentation, cytoskeletal disassembly, nuclear condensation, and formation of apoptotic bodies.
(2) ICAD-CAD pathway
GZMB can mediate ICAD cleavage through caspase-3, releasing CAD endonuclease and promoting DNA fragmentation. TUNEL positivity, DNA laddering, and increased cleaved PARP are commonly used to support this process.
(3) Experimental validation
GZMB-related apoptosis should be judged by combining cleaved caspase-3, cleaved PARP, Annexin V, TUNEL, and decreased target cell viability. If apoptosis decreases after treatment with a GZMB inhibitor or PRF1 blockade, this further supports the causal role of this pathway.
2.3 GZMB-Mitochondrial Amplification Pathway
(1) Bid cleavage
GZMB can cleave Bid to generate tBid. After translocating to mitochondria, tBid promotes BAX/BAK-mediated mitochondrial outer membrane permeabilization, leading to cytochrome c release into the cytoplasm.
(2) Apoptosome formation
After cytochrome c release, cytochrome c cooperates with Apaf-1 and caspase-9 to participate in apoptosome formation, further activating caspase-3. This process expands GZMB-mediated killing from direct caspase activation into a mitochondrial amplification response.
(3) Target cell sensitivity
Anti-apoptotic proteins such as Bcl-2, Bcl-xL, and Mcl-1 can reduce the sensitivity of target cells to GZMB. In tumor cells, high expression of anti-apoptotic proteins may lead to CTL infiltration and increased GZMB, but insufficient target cell apoptosis.
3、Death Receptor-Mediated Apoptosis Pathway
(1) FasL expression
Activated CTLs can express Fas ligand (FasL/CD95L), which binds Fas (CD95) on the surface of target cells. This pathway does not depend on granzyme entry into the cytoplasm and can directly initiate apoptotic signaling through the death receptor complex.
(2) DISC formation
After Fas activation, FADD is recruited to form the death-inducing signaling complex (DISC), which then activates caspase-8. Caspase-8 can directly activate caspase-3 or cleave Bid and connect to the mitochondrial apoptosis pathway.
(3) Functional characteristics
The Fas/FasL axis often participates in chronic killing, autoimmune tissue injury, transplant rejection, and immune homeostasis regulation. Compared with the perforin-granzyme axis, this pathway is more dependent on Fas expression in target cells and the integrity of death receptor signaling.
3.2 TNF-Related Death Signaling
(1) TNF-TNFR1 signaling
CTLs can release TNF-α. After TNF-α binds TNFR1, it may initiate NF-κB survival signaling, inflammatory signaling, or caspase-8-mediated apoptotic signaling depending on the cellular context.
(2) Branching between inflammation and death
TNF signaling does not always directly induce apoptosis. When NF-κB is active, TNF is more likely to promote inflammatory factor expression and cell survival. When survival signaling is blocked or the caspase-8 pathway predominates, TNF can promote target cell apoptosis.
(3) Research interpretation
Increased TNF-α alone cannot prove CTL-induced apoptosis. TNFR1, FADD, caspase-8, cleaved caspase-3, NF-κB activation status, and target cell death outcomes should be interpreted together.
Table 1 Comparison of Major Pathways in Killer T Cell-Mediated Apoptosis
Pathway | Key molecules | Main death mechanism | Typical detection indicators | Interpretation focus |
Perforin-granzyme B axis | PRF1, GZMB, caspase-3, Bid | Direct caspase activation and mitochondrial apoptosis amplification | PRF1, GZMB, cleaved caspase-3, tBid, TUNEL | Most typical rapid CTL killing mechanism |
Granzyme A-related injury | PRF1, GZMA, ROS, SET complex | Non-caspase-dependent injury, oxidative stress, and inflammatory amplification | GZMA, ROS, γH2AX, Comet assay | Should not be evaluated only by apoptosis indicators |
Fas/FasL axis | FasL, Fas, FADD, caspase-8 | Death receptor-mediated apoptosis | FasL, Fas, cleaved caspase-8, cleaved caspase-3 | Depends on Fas expression in target cells |
TNF/TNFR1 axis | TNF-α, TNFR1, FADD, caspase-8 | Branching into inflammation, survival, or apoptosis | TNF-α, TNFR1, NF-κB, caspase-8 | Distinguish inflammatory activation from death signaling |
4、Execution Stage of Target Cell Apoptosis
4.1 Caspase Cascade
(1) Initiator caspases
Caspase-8 and caspase-9 represent important initiation nodes of the death receptor pathway and mitochondrial pathway, respectively. In CTL-mediated apoptosis, both may participate simultaneously, or one pathway may predominate depending on the source of stimulation.
(2) Executioner caspases
Caspase-3 and caspase-7 are important molecules in the execution stage of apoptosis. After activation, they cleave PARP, cytoskeletal proteins, and nuclear structure-related proteins, leading to typical apoptotic morphology.
(3) Detection combination
When studying target cell apoptosis, a single caspase should not be detected alone. A more complete combination includes cleaved caspase-8, cleaved caspase-9, cleaved caspase-3, cleaved PARP, Annexin V/PI, and TUNEL.
4.2 Mitochondrial Pathway
(1) BAX/BAK activation
tBid or other BH3-only proteins can promote BAX/BAK oligomerization and increase mitochondrial outer membrane permeabilization. This process is a key step in the intrinsic apoptosis pathway.
(2) Cytochrome c release
After mitochondrial outer membrane permeabilization, cytochrome c is released into the cytoplasm and promotes the formation of the apoptosome with Apaf-1 and caspase-9. Decreased mitochondrial membrane potential is commonly used as a functional readout of this stage.
(3) Anti-apoptotic regulation
Increased anti-apoptotic Bcl-2 family proteins in target cells can weaken CTL-mediated apoptosis. Tumor cells often use this mechanism to evade immune killing.
4.3 DNA Damage and Apoptosis Endpoints
(1) DNA fragmentation
The GZMB-caspase-CAD axis can cause DNA fragmentation, which is one of the terminal features of typical apoptosis. TUNEL and DNA laddering can be used to detect this change.
(2) Membrane phospholipid externalization
Annexin V can recognize externalized phosphatidylserine and is suitable for detecting early apoptosis. When combined with PI or 7-AAD, it can distinguish early apoptosis, late apoptosis, and necrosis-like death.
(3) Morphological evidence
Nuclear condensation, nuclear fragmentation, cell shrinkage, and formation of apoptotic bodies are important morphological evidence. In tissue samples, cell source, spatial proximity, and target cell markers should be combined as much as possible for interpretation.
5、Disease and Research Application Scenarios
5.1 Antiviral Immunity
(1) Clearance of infected cells
After virus-infected cells present viral antigens through MHC I, they can be recognized and cleared by CTLs. Effective CTL responses usually show CD8⁺ T cell expansion, PRF1/GZMB upregulation, IFN-γ release, and increased apoptosis of infected cells.
(2) Chronic infection status
In chronic infection, CD8⁺ T cells may show increased exhaustion markers such as PD-1, TIM-3, and LAG-3. In this situation, even if the number of CTLs increases, their killing capacity may decrease.
(3) Interpretation indicators
Antiviral studies should analyze CTL killing indicators together with viral load, proportion of infected cells, tissue injury, and T cell exhaustion status. If GZMB increases but viral load does not decrease, effective antiviral killing cannot be directly concluded.
5.2 Tumor Immunity
(1) Tumor cell recognition
Tumor cells can present tumor antigens or neoantigens through MHC I and be recognized by CD8⁺ T cells. If tumor-infiltrating CD8⁺ T cells show increased GZMB, PRF1, and IFN-γ, this usually suggests enhanced antitumor cytotoxic responses.
(2) Immune escape
Tumors can evade CTL-mediated apoptosis through MHC I downregulation, antigen processing defects, PD-L1 upregulation, TGF-β enrichment, increased Treg and MDSC populations, and increased anti-apoptotic Bcl-2 family proteins.
(3) Immunotherapy evaluation
After immune checkpoint inhibitor therapy, if CD8⁺ T cell infiltration increases, GZMB/PRF1 is upregulated, target cell TUNEL or cleaved caspase-3 signals increase, and tumor burden decreases, this more strongly supports therapy-induced effective CTL killing.
5.3 Transplant Rejection and Autoimmunity
(1) Transplant rejection
In transplanted tissues, CTLs can recognize alloantigens and induce apoptosis of graft cells through GZMB, PRF1, and FasL. Colocalization of CD8⁺ T cell infiltration, GZMB positivity, and target cell apoptosis in tissues has strong suggestive value.
(2) Autoimmune injury
In autoimmune diseases, CTLs may mistakenly damage self-tissue cells. In this context, cytotoxic pathways are both immune effector mechanisms and sources of tissue injury.
(3) Tissue interpretation
In autoimmune and transplant samples, CTL-mediated apoptosis should be interpreted comprehensively using CD8, GZMB, FasL, PRF1, cleaved caspase-3, TUNEL, and histopathological injury scores.
6、Experimental Detection Strategies and Related Product Selection
6.1 Effector Cell Detection
(1) CTL source
Flow cytometry can detect the proportion of CD3⁺CD8⁺ T cells and further analyze GZMB, PRF1, IFN-γ, TNF-α, and CD107a. Tissue samples can be analyzed by multiplex immunofluorescence of CD8, GZMB, and PRF1 to observe spatial localization.
(2) Activation status
CD69, CD25, CD44, CD137, IFN-γ, and IL-2 can be used to analyze CTL activation. PD-1, TIM-3, LAG-3, and TIGIT can be used to analyze exhaustion or inhibitory states.
(3) Degranulation capacity
CD107a externalization is an important indicator for judging CTL granule release. High GZMB expression with low CD107a suggests that cytotoxic granule reserves exist, but release is insufficient.
6.2 Target Cell Death Detection
(1) Apoptosis indicators
Target cell death can be evaluated by Annexin V/PI, cleaved caspase-3, cleaved PARP, TUNEL, mitochondrial membrane potential, and cell viability assays.
(2) Target cell distinction
In co-culture systems, CTLs and target cells need to be distinguished. Target cell fluorescent labeling, tumor cell-specific markers, or flow cytometry gating strategies can be used to avoid misidentifying effector cell death as target cell apoptosis.
(3) Spatial colocalization
In tissue samples, the spatial proximity between CD8⁺GZMB⁺ cells and cleaved caspase-3⁺ or TUNEL⁺ target cells should be analyzed. Counting CD8- or GZMB-positive cells alone is insufficient to prove direct CTL killing.
6.3 Functional Blockade and Causal Validation
(1) Perforin blockade
PRF1 inhibition or PRF1-deficient models can be used to validate perforin dependence. If GZMB-related apoptosis decreases after PRF1 blockade, this indicates that granzyme entry into target cells is a key step.
(2) GZMB blockade
GZMB inhibitors, GZMB knockdown, or GZMB deficiency can be used to verify whether caspase-dependent apoptosis is driven by GZMB. Cleaved caspase-3, PARP cleavage, and TUNEL changes should be detected simultaneously.
(3) Fas/FasL blockade
FasL neutralizing antibodies, Fas knockdown, or FADD/caspase-8 intervention can be used to validate the death receptor pathway. If apoptosis decreases after Fas/FasL blockade, it indicates that the death receptor axis participates in CTL-mediated killing.
Table 2 Common Detection Combinations for Killer T Cell-Mediated Apoptosis Pathway Studies
Research purpose | Recommended detection combination | Main interpretation |
Determine CTL infiltration | CD3, CD8, GZMB, PRF1 | Determines whether cytotoxic T cells enter the lesion |
Determine CTL activation | CD69, CD25, IFN-γ, TNF-α, CD137 | Reflects T cell activation and effector status |
Determine degranulation | CD107a, GZMB, PRF1 | Determines whether cytotoxic granules are released |
Determine GZMB-mediated apoptosis | GZMB, cleaved caspase-3, cleaved PARP, TUNEL | Determines whether granzyme B-mediated apoptosis occurs |
Determine Fas/FasL pathway | FasL, Fas, FADD, cleaved caspase-8 | Determines whether the death receptor pathway participates |
Determine mitochondrial involvement | tBid, BAX, Bcl-2, cytochrome c, JC-1 | Determines whether intrinsic apoptosis is amplified |
Determine immune escape | MHC I, PD-L1, PD-1, Bcl-2, Mcl-1 | Determines possible causes of insufficient killing |
Determine spatial killing | Colocalization of CD8/GZMB with TUNEL or cleaved caspase-3 | Determines whether CTLs are spatially associated with dying target cells |
6.4 Related Reagent and Detection Tool Selection
Table 3 Reagents and Detection Tools Related to the Killer T Cell-Mediated Apoptosis Pathway
Cat. No. | Product Name | Grade/Specification | Product category | Corresponding pathway link | Application positioning |
TCR α/β Mouse mAb | Carrier Free,Azide Free,Validated,PBS Only,≥95%(SDS-PAGE),See COA | TCR antibody | TCR-mediated target cell recognition | Used to identify αβ T cell populations; suitable for analyzing CTL origin and TCR-dependent killing responses | |
TCR α/β Mouse mAb (AF647) | ExactAb™, Validated, Ex:650nm, Em:668nm, 0.5 mg/mL | Fluorescent-labeled TCR antibody | TCR-mediated target cell recognition | Used for flow cytometry or immunofluorescence detection of αβ T cells | |
TCR α/β Mouse mAb (APC) | ExactAb™, Validated, Ex:650nm, Em:660nm, 0.5 mg/mL | Fluorescent-labeled TCR antibody | TCR-mediated target cell recognition | Used for flow cytometric analysis of CTL populations and their relationship with apoptotic target cells | |
TCR α/β Mouse mAb (FITC) | ExactAb™, Validated, Ex:498nm, Em:517nm, 0.5 mg/mL | Fluorescent-labeled TCR antibody | TCR-mediated target cell recognition | Used for T cell subset detection and effector cell identification in co-culture systems | |
TCR α/β Mouse mAb (PE) | ExactAb™, Validated, 0.5 mg/mL | Fluorescent-labeled TCR antibody | TCR-mediated target cell recognition | Used for flow cytometric detection of TCRαβ-positive T cells | |
TCR beta Armenian Hamster mAb | Carrier Free,ExactAb™,Azide Free,Validated,PBS Only,See COA | TCRβ antibody | TCR complex detection | Used to detect TCRβ expression and assist analysis of TCR-dependent CTL recognition | |
TOL101 (anti-TCR) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥95%(SDS-PAGE&SEC-HPLC), See COA | Anti-TCR antibody/functional tool | TCR signal regulation | Used for TCR-related functional regulation studies | |
CD3 Mouse mAb | Carrier Free, ExactAb™, Validated, See COA | CD3 antibody | TCR-CD3 complex | Used to detect overall T cell infiltration | |
CD3 Mouse mAb | Carrier Free,Azide Free,Validated,PBS Only,≥95%(SDS-PAGE),See COA | CD3 antibody | TCR-CD3 complex | Used for T cell detection, tissue infiltration analysis, and TCR-CD3 pathway studies | |
CD3 Mouse mAb (AF647) | ExactAb™, Validated, Ex:650nm, Em:668nm, 5 μL/test | Fluorescent-labeled CD3 antibody | T cell recognition and grouping | Used for flow cytometry or immunofluorescence detection of CD3⁺ T cells | |
CD3 Mouse mAb (APC) | ExactAb™, Validated, Ex:650nm, Em:660nm, 5 μL/test | Fluorescent-labeled CD3 antibody | T cell recognition and grouping | Used for CTL infiltration and T cell origin determination | |
CD3 Mouse mAb (FITC) | ExactAb™, Validated, Ex:498nm, Em:517nm, 0.1 mg/mL | Fluorescent-labeled CD3 antibody | T cell recognition and grouping | Used for flow cytometric detection of CD3⁺ T cells | |
CD3 Mouse mAb (PE) | ExactAb™, Validated, Ex:565nm, Em:575nm, 5 μL/test | Fluorescent-labeled CD3 antibody | T cell recognition and grouping | Used for multicolor flow cytometric analysis of T cell infiltration and activation status | |
CD3 Rat mAb | Carrier Free,ExactAb™,Azide Free,Validated,PBS Only,See COA | CD3 antibody | TCR-CD3 complex | Used for T cell detection and tissue localization in mouse or rat models | |
CD3 epsilon Mouse mAb | Carrier Free, ExactAb™, Validated, High Performance, See COA | CD3ε antibody | TCR-CD3 signaling complex | Used to analyze initiation of TCR-CD3 signaling | |
CD3 epsilon Syrian Hamster mAb | Carrier Free,Low Endotoxin,Azide Free,Validated,PBS Only,≥95%(SDS-PAGE&HPLC),See COA | CD3ε antibody | TCR-CD3 signaling complex | Used for T cell recognition, activation, or functional regulation studies | |
CD3 zeta Antibody | ExactAb™, Validated, Carrier Free, High performance, 0.5 mg/mL | CD3ζ antibody | TCR downstream signal transduction | Used to analyze TCR-CD3 complex signal transduction | |
CD3D Human Pre-designed siRNA Set A |
| siRNA | CD3δ gene silencing | Used to verify the role of the TCR-CD3 complex in CTL-mediated apoptosis | |
CD3E Human Pre-designed siRNA Set A |
| siRNA | CD3ε gene silencing | Used to analyze the effects of TCR-CD3 signaling on CTL activation and target cell apoptosis | |
CD3G Human Pre-designed siRNA Set A |
| siRNA | CD3γ gene silencing | Used to verify the effect of TCR-CD3 complex integrity on the killing pathway | |
Recombinant Human CD3 delta/CD3d Protein | Animal Free,Carrier Free,Bioactive,ActiBioPure™,His Tag,≥95%(SDS-PAGE) | Recombinant CD3 protein | TCR-CD3 complex tool protein | Used for antibody validation, binding assays, or TCR-CD3 method development | |
Recombinant Human CD3 epsilon Protein | Animal Free,Carrier Free,Bioactive,ActiBioPure™,His Tag,PBS Only,≥90%(SDS-PAGE),See COA | Recombinant CD3 protein | TCR-CD3 complex tool protein | Used for validation of CD3ε-related detection systems | |
Recombinant Human CD3 gamma Protein | Animal Free,Carrier Free,Bioactive,ActiBioPure™,Fc tag,PBS Only,≥90%(SDS-PAGE),See COA | Recombinant CD3 protein | TCR-CD3 complex tool protein | Used for CD3γ-related antibody or binding system validation | |
Recombinant Human CD3 zeta/CD247 Protein | Carrier Free,Bioactive,ActiBioPure™,His Tag,≥90%(SDS-PAGE),See COA | Recombinant CD3ζ/CD247 protein | TCR signal transduction tool protein | Used for TCR-CD3 downstream signaling studies | |
Muromonab (anti-CD3) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥95%(SDS-PAGE&SEC-HPLC), See COA | Anti-CD3 antibody/functional tool | T cell activation or regulation | Can be used for T cell activation, CD3 functional regulation, and CTL-mediated apoptosis model studies | |
Teplizumab (anti-CD3e) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥95%(SDS-PAGE&SEC-HPLC), See COA | Anti-CD3ε antibody/functional tool | TCR-CD3 regulation | Used to analyze T cell activation threshold and changes in cytotoxic effects | |
Foralumab (anti-CD3E) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥95%(SDS-PAGE&SEC-HPLC), See COA | Anti-CD3E antibody/functional tool | TCR-CD3 regulation | Used to analyze CTL function in T cell activation or immune regulation models | |
Otelixizumab (anti-CD3) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥95%(SDS-PAGE&SEC-HPLC), See COA | Anti-CD3 antibody/functional tool | T cell function regulation | Used in TCR-CD3-related regulatory experiments | |
Blinatumomab (anti-CD3&CD19) | Animal Free,Carrier Free,Recombinant,ExactAb™,Low Endotoxin,Azide Free,Moligand™,Validated,PBS Only,≥90%(SDS-PAGE&SEC-HPLC),See COA | CD3 bispecific antibody | T cell-redirected killing | Used to construct CD3-mediated T cell-redirected killing models | |
Catumaxomab (anti-CD3&EpCAM) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥90%(SDS-PAGE&SEC-HPLC), See COA | CD3 bispecific antibody | T cell-redirected killing | Used for T cell-mediated killing studies of EpCAM-positive target cells | |
Epcoritamab (anti-CD3&CD20) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥90%(SDS-PAGE&SEC-HPLC), See COA | CD3 bispecific antibody | T cell-redirected killing | Used in co-culture killing models involving CD20-positive target cells and T cells | |
Mosunetuzumab (anti-CD20&CD3e) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥90%(SDS-PAGE&SEC-HPLC), See COA | CD3 bispecific antibody | T cell-redirected killing | Used in CD20-targeted T cell killing experiments | |
Odronextamab (anti-CD20&CD3) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥90%(SDS-PAGE&SEC-HPLC), See COA | CD3 bispecific antibody | T cell-redirected killing | Used for T cell-mediated apoptosis models of CD20-positive target cells | |
Linvoseltamab (anti-BCMA&CD3) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥90%(SDS-PAGE&SEC-HPLC), See COA | CD3 bispecific antibody | T cell-redirected killing | Used for CTL-like killing studies of BCMA-positive target cells | |
Teclistamab (anti-CD3&BCMA) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥90%(SDS-PAGE&SEC-HPLC), See COA | CD3 bispecific antibody | T cell-redirected killing | Used to analyze induction of target cell apoptosis after CD3-bridged T cell engagement | |
Tarlatamab (anti-DLL3&CD3) | Animal Free,Carrier Free,Recombinant,ExactAb™,Low Endotoxin,Azide Free,Validated,PBS Only,≥90%(SDS-PAGE&SEC-HPLC),See COA | CD3 bispecific antibody | T cell-redirected killing | Used for T cell-mediated apoptosis models of DLL3-positive target cells | |
Tidutamab (anti-CD3&SSTR2) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥90%(SDS-PAGE&SEC-HPLC), See COA | CD3 bispecific antibody | T cell-redirected killing | Used for T cell-bridged killing studies of SSTR2-positive target cells | |
Cevostamab (anti-CD3&FCRL5) | Carrier Free, Recombinant, ExactAb™, Low Endotoxin, Azide Free, Validated, Animal Free, ≥90%(SDS-PAGE&SEC-HPLC), See COA | CD3 bispecific antibody | T cell-redirected killing | Used for T cell-mediated apoptosis studies of FCRL5-positive target cells | |
NKG2D/CD314 Rat mAb | Carrier Free,Azide Free,Validated,PBS Only,≥95%(SDS-PAGE),See COA | NKG2D antibody | Cytotoxic lymphocyte activating receptor | Used to analyze activation receptors related to CD8⁺ T cells/NK cells | |
NKG2D/CD314 Rat mAb (AF488) | ExactAb™, Validated, 0.5 mg/mL | Fluorescent-labeled NKG2D antibody | Cytotoxic lymphocyte activating receptor | Used for flow cytometry or immunofluorescence detection of NKG2D-positive cytotoxic lymphocytes | |
NKG2D/CD314 Rat mAb (AF647) | ExactAb™, Validated, 0.5 mg/mL | Fluorescent-labeled NKG2D antibody | Cytotoxic lymphocyte activating receptor | Used for multicolor flow cytometric analysis of CTL/NK-related activation status | |
TIM 3/CD366 Mouse mAb | Carrier Free,ExactAb™,Azide Free,Validated,PBS Only,See COA | TIM-3 antibody | T cell exhaustion/inhibitory status | Used to detect TIM-3 and assist evaluation of suppressed CD8⁺ T cell function | |
TIM 3/CD366 Mouse mAb (APC) | ExactAb™, Validated, Ex:650nm, Em:660nm, 5 μL/test | Fluorescent-labeled TIM-3 antibody | T cell exhaustion/inhibitory status | Used for flow cytometric analysis of TIM-3-positive T cells | |
TIM 3/CD366 Mouse mAb (FITC) | ExactAb™, Validated, Ex:498nm, Em:517nm, 5 μL/test | Fluorescent-labeled TIM-3 antibody | T cell exhaustion/inhibitory status | Used for detection of T cell exhaustion phenotype | |
TIM 3/CD366 Mouse mAb (PE) | ExactAb™, Validated, Ex:565nm, Em:575nm, 5 μL/test | Fluorescent-labeled TIM-3 antibody | T cell exhaustion/inhibitory status | Used for multicolor flow cytometry to detect relationships among TIM-3, CD3, and apoptosis endpoints | |
TIM3/CD366 Rat mAb | Carrier Free,Azide Free,Validated,PBS Only,≥95%(SDS-PAGE),See COA | TIM-3 antibody | T cell exhaustion/inhibitory status | Used for detection of T cell inhibitory status in animal models | |
GITR/CD357 Rat mAb | Carrier Free,Azide Free,Validated,PBS Only,≥95%(SDS-PAGE),See COA | GITR antibody | T cell co-stimulation/regulation | Used to analyze T cell activation and regulatory status | |
GITR/CD357 Rat mAb (AF647) | ExactAb™, Validated, Ex:650nm, Em:668nm, 0.5 mg/mL | Fluorescent-labeled GITR antibody | T cell co-stimulation/regulation | Used for flow cytometric detection of GITR-positive T cells | |
GITR/CD357 Rat mAb (APC) | ExactAb™, Validated, Ex:650nm, Em:660nm, 0.5 mg/mL | Fluorescent-labeled GITR antibody | T cell co-stimulation/regulation | Used to detect T cell activation/regulatory status | |
GITR/CD357 Rat mAb (FITC) | ExactAb™, Validated, Ex:498nm, Em:517nm, 0.5 mg/mL | Fluorescent-labeled GITR antibody | T cell co-stimulation/regulation | Used for multicolor flow cytometric analysis of T cell functional status | |
GITR/CD357 Rat mAb (PE) | ExactAb™, Validated, 0.5 mg/mL | Fluorescent-labeled GITR antibody | T cell co-stimulation/regulation | Used to detect GITR-related T cell activation background | |
Caspase 3 Mouse mAb | Carrier Free,ExactAb™,Azide Free,Validated,High Performance,PBS Only,≥95%(SDS-PAGE),1.0 mg/mL | Caspase-3 antibody | Apoptosis execution stage | Used to detect caspase-3 expression | |
Caspase 3 Mouse mAb | Carrier Free,ExactAb™,Azide Free,Validated,High Performance,PBS Only,≥95%(SDS-PAGE),1.0 mg/mL | Caspase-3 antibody | Apoptosis execution stage | Used for target cell apoptosis pathway detection and tissue sample analysis | |
Recombinant Caspase3 Antibody | ExactAb™, Validated, Recombinant, 0.9mg/mL | Caspase-3 antibody | Apoptosis execution stage | Used to detect caspase-3 and assist determination of whether apoptosis has entered the execution stage | |
Recombinant Caspase3 Antibody | ExactAb™, Recombinant, Validated, KD Validation, See COA | Caspase-3 antibody | Apoptosis execution stage | Used for caspase-3 detection and methodological validation | |
Recombinant Caspase 3 p12 Antibody | KD Validation | Caspase-3 cleavage fragment antibody | Apoptosis execution stage | Used to recognize caspase-3 activation-related fragments | |
Recombinant active + pro caspase 3 Antibody | KD Validation | Active/pro-caspase-3 antibody | Apoptosis execution stage | Used to distinguish caspase-3 precursor and activated states | |
Pro caspase 3 Antibody | KD Validation | Pro-caspase-3 antibody | Pre-execution apoptosis status | Used to analyze pro-caspase-3 levels | |
Caspase 3 Activity Assay Kit | BioReagent,Colorimetry,Suitable for Analysis | Caspase-3 activity kit | Apoptosis execution stage | Used for colorimetric detection of caspase-3 activity | |
Caspase 3/7 Activity Assay Kit | BioReagent | Caspase-3/7 activity kit | Apoptosis execution stage | Used to detect caspase-3/7 activity | |
aladdin™ 488 caspase-3 live cell assay kit |
| Live-cell caspase-3 analysis kit | Live-cell apoptosis detection | Used for live-cell imaging analysis of caspase-3 activation | |
Human Caspase 3 (CASP3) ELISA Kit | BioReagent | ELISA kit | Caspase-3 quantitative detection | Used to detect CASP3 levels in human-derived samples | |
Rat Caspase 3 (CASP3) ELISA Kit | BioReagent | ELISA kit | Caspase-3 quantitative detection | Used to detect CASP3 levels in rat models | |
Mouse Caspase 3 (CASP3) ELISA Kit | BioReagent | ELISA kit | Caspase-3 quantitative detection | Used to detect CASP3 in mouse tumor, infection, or transplant models | |
Caspase-3/7 Inhibitor | ≥97% | Caspase-3/7 inhibitor | Apoptosis execution stage blockade | Used to verify whether target cell death depends on the caspase-3/7 execution pathway | |
Caspase-3-IN-1 | Moligand™, 10 mM in DMSO | Caspase-3 inhibitor | Apoptosis execution stage blockade | Used to inhibit caspase-3 and verify caspase dependence of apoptosis | |
Caspase-3 activator 2 |
| Caspase-3 activator | Apoptosis execution stage regulation | Can serve as a positive regulatory tool for establishing caspase-3-mediated apoptosis models | |
Caspase-3 activator 3 |
| Caspase-3 activator | Apoptosis execution stage regulation | Used to induce caspase-3 activation | |
Caspase-3 activator 4 |
| Caspase-3 activator | Apoptosis execution stage regulation | Used as a positive control for caspase-3-dependent apoptosis studies | |
Caspase-3/7 activator 1 |
| Caspase-3/7 activator | Apoptosis execution stage regulation | Used to activate executioner caspases | |
Caspase-3/7 activator 2 |
| Caspase-3/7 activator | Apoptosis execution stage regulation | Used for caspase-3/7 activity-related methodological validation | |
Caspase-3/7 activator 3 |
| Caspase-3/7 activator | Apoptosis execution pathway positive control | Used as a positive control for the apoptosis execution pathway | |
Procaspase-3/6 activator 1 | Moligand™, 10 mM in DMSO | Procaspase activator | Apoptosis execution stage regulation | Used to induce procaspase-3/6 activation | |
Recombinant Human Caspase-3 Protein | ≥90%(SDS-PAGE) | Recombinant caspase-3 protein | Apoptosis execution stage tool protein | Used for antibody validation, enzymology studies, or apoptosis detection system development | |
Recombinant Human Caspase-3 Protein | Carrier Free,His Tag,≥90%(SDS-PAGE) | Recombinant caspase-3 protein | Apoptosis execution stage tool protein | Used for caspase-3-related experimental system validation | |
Live Cell Caspase-3/7 Activity and Annexin V Dual Apoptosis Detection Kit (LumiDye™ 488 Caspase-3/7, LumiDye™ 594-Annexin V, Hoechst 33342) | BioReagent,sterile,for microscopy,Biological Stain,for fluorescence analysis | Live-cell apoptosis assay kit | Caspase-3/7 activity and early apoptosis | Used to simultaneously detect caspase-3/7 activation, Annexin V positivity, and nuclei | |
Live Cell Caspase-3/7 Activity and Annexin V Dual Apoptosis Detection Kit (LumiDye™ 488 Caspase-3/7, LumiDye™ 647-Annexin V, EthD Gold) | BioReagent,Biological Stain,for microscopy,sterile,for fluorescence analysis | Live-cell apoptosis assay kit | Caspase-3/7 activity and membrane integrity | Used to distinguish early apoptosis, late apoptosis, and dead cells | |
Live Cell Caspase-3/7 Activity and Annexin V Dual Apoptosis Detection Kit (LumiDye™ 488 Caspase-3/7, LumiDye™ 647-Annexin V, EthD Gold, Hoechst 33342) | BioReagent,sterile,for microscopy,Biological Stain,for fluorescence analysis | Live-cell apoptosis assay kit | Caspase-3/7 activity, Annexin V, and nuclear staining | Used for comprehensive evaluation of CTL-mediated target cell apoptosis progression | |
Live Cell Caspase-3/7 Activity and Annexin V Dual Apoptosis Detection Kit (LumiDye™ 488 Caspase-3/7, LumiDye™ 647-Annexin V, Hoechst 33342) | BioReagent,Biological Stain,for microscopy,sterile,for fluorescence analysis | Live-cell apoptosis assay kit | Caspase-3/7 activity and Annexin V detection | Used to detect T cell-mediated apoptosis in live-cell systems |
7、Result Interpretation and Research Design Recommendations
7.1 Common Result Combinations
(1) Increased CD8⁺ T cells, elevated GZMB and PRF1, and enhanced target cell apoptosis
This combination supports enhanced CTL-mediated cytotoxic killing. If tumor burden or viral load also decreases, the functional conclusion is more reliable.
(2) Increased CD8⁺ T cells and elevated GZMB, but insufficient target cell apoptosis
This combination suggests that CTL infiltration does not necessarily translate into effective killing. Possible causes include T cell exhaustion, insufficient PRF1, impaired degranulation, MHC I downregulation, PD-L1-mediated inhibition, or enhanced anti-apoptotic capacity of target cells.
(3) Increased Fas/FasL with activation of caspase-8 and caspase-3
This combination supports the involvement of death receptor-mediated apoptosis in killing. If GZMB changes are not obvious, the killing process may rely more on the Fas/FasL axis.
(4) Increased TNF-α without obvious apoptosis indicators
This combination is more likely to indicate inflammatory activation rather than enhanced apoptosis. NF-κB, caspase-8, and target cell death endpoints should be further detected.
7.2 Key Points in Research Design
(1) Avoid single-indicator judgment
Increased CD8, GZMB, or IFN-γ alone only indicates enhanced cytotoxic immunity-related signals and cannot directly prove that target cells have undergone apoptosis. A complete evidence chain should include effector cells, cytotoxic molecules, degranulation, death pathways, and target cell endpoints.
(2) Distinguish killing from inflammation
CTLs can release GZMB, IFN-γ, and TNF-α simultaneously. GZMB is more directly associated with target cell apoptosis, while IFN-γ and TNF-α can also promote inflammation, antigen presentation, and tissue injury. Studies should distinguish “enhanced cytotoxic killing” from “enhanced inflammatory response.”
(3) Emphasize target cell status
MHC I expression, antigen processing capacity, Fas expression, Bcl-2 family protein levels, and PD-L1 expression in target cells all influence CTL-mediated apoptosis. Analyzing only T cell-side indicators can easily underestimate target cell resistance mechanisms.
The core of the killer T cell-mediated apoptosis pathway lies in antigen-specific recognition of abnormal target cells by CTLs and the initiation of target cell death programs through perforin-granzyme, Fas/FasL, and TNF-related signals. The GZMB-caspase axis represents rapid and typical apoptotic killing, while the Fas/FasL axis plays an important role in death receptor-dependent apoptosis and chronic tissue injury.
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[4] Metabolic signaling pathway
[5] Wnt Signaling