BRAINCAKEThe Cell-Mediated Response
The cell-mediated response is the part of the specific immune response carried out by T lymphocytes. It acts against body cells that display non-self antigens: cells infected by viruses or by bacteria that live inside cells (such as Mycobacterium tuberculosis), cancer cells and transplanted cells. Antibodies cannot reach pathogens inside cells, so this response is essential.
The sequence:
1. Antigen presentation: infected body cells display fragments of the pathogen's antigens on MHC proteins on their cell surface membrane. Macrophages that have engulfed pathogens also present antigens.
2. Selection: T helper cells and T killer cells with receptors complementary to the presented antigen bind to it.
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Key terms in this lesson
- cytokine
- A small signalling protein released by cells, especially of the immune system, that influences the behaviour of other cells.
- mhc protein
- A protein displayed on the surface of body cells that presents antigen fragments to T cells, allowing self to be distinguished from non-self.
More in Response to Infection
- The Humoral Response
- The Effector Stage
- Clonal Selection
- Antibodies
- Cytotoxic T Cells
- Primary and Secondary Immune Response
- Types of Immunity
- Artificial Passive Immunity
All 20 lessons in Response to Infection · All Edexcel A-level Biology topics