Helper T Cell
Definition
A CD4+ T lymphocyte that recognises antigen on MHC class II molecules and secretes cytokines that amplify both the humoral and cellular arms of the immune response. Without helper T cell activation, B cells cannot mount a full antibody response to protein antigens.
- Surface marker
- CD4+
- Recognises
- Antigen on MHC class II molecules
- Function
- Secretes cytokines amplifying immune response
- Required for
- Full B cell antibody response to protein antigens
Common questions
Why does helper T cell activity matter for forensic serology testing?+
Antibody-based forensic tests such as species and blood identification rely on the humoral response helper T cells help generate, so this pathway underlies why immunological reagents like anti-human haemoglobin antibodies work as species-specific markers.
What distinguishes a helper T cell from a cytotoxic T cell in the immune response?+
A helper T cell (CD4+) coordinates and amplifies other immune cells through cytokine signalling rather than killing infected cells directly, while a cytotoxic T cell (CD8+) recognises antigen on MHC class I and destroys the presenting cell.
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...
- Cytotoxic T Cell (CTL)
- A CD8+ T lymphocyte that recognises peptide antigens presented on MHC class I molecules and kills the target cell by releasing perforin...
- 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...