# 61 Action of T-lymphocytes

T-lymphocytes include T helper cells and T killer cells. Both of these types of cell place their specific receptors in their cell surface membranes. On encountering the relevant antigen, they are activated and divide by mitosis to form a clone.

Activated T helper cells secrete chemicals called cytokines. These stimulate B-lymphocytes to produce plasma cells, and stimulate monocytes and macrophages to attack and destroy pathogens.

Activated T killer (cytotoxic) cells attach to body cells that display the antigen matching their receptor. This happens when a body cell has been invaded by a virus. The T killer cell destroys the infected body cell.

Someof the clone of T cells become memory cells, which remain in the body and can react swiftly if the same pathogen invades again.

Syllabus 2015   • The immune system (c) describe the modes of action of T-lymphocytes;

Syllabus 2016 - 2018 11.1  The immune system b)   describe the modes of action of T-lymphocytes