Cytotoxic T Cell (CTL)
Definition
A CD8+ T lymphocyte that recognises peptide antigens presented on MHC class I molecules and kills the target cell by releasing perforin and granzymes. Historically relevant to forensic relationship testing through histocompatibility typing before DNA methods became standard.
- Marker
- CD8+
- Recognises
- Peptide antigens on MHC class I
- Killing mechanism
- Perforin and granzyme release
- Historical forensic use
- Histocompatibility typing before DNA methods
Common questions
Why was histocompatibility typing eventually replaced by DNA-based methods in forensic paternity and identity testing?+
DNA typing offers far greater individual discrimination and does not require live or viable cells the way histocompatibility assays did, so it displaced cellular immune typing once PCR-based STR methods became reliable and widely available.
How does a cytotoxic T cell differ functionally from a helper T cell in this context?+
A cytotoxic T cell directly kills cells presenting foreign or abnormal peptides via MHC class I, while a helper T cell coordinates the wider immune response by recognising MHC class II antigens and signalling other immune cells rather than killing targets itself.
Related terms
- Affinity Maturation
- The progressive increase in antibody-antigen binding strength that occurs during the secondary and subsequent responses. It results from somatic hypermutation of immunoglobulin...
- Clonal Selection
- The process by which an antigen binds selectively to the lymphocyte (B or T cell) that carries the complementary surface receptor, triggering...
- Helper T Cell
- A CD4+ T lymphocyte that recognises antigen on MHC class II molecules and secretes cytokines that amplify both the humoral and cellular...
- Memory B Cell
- A long-lived B cell generated during a primary immune response that retains the antigen-specific receptor and persists in lymphoid tissue. On re-exposure...
- Plasma Cell
- A terminally differentiated B cell that has lost most of its surface immunoglobulin and become a high-output antibody factory, secreting thousands of...