T Lymphocytes

T Lymphocytes:
• thymus derived lymphocyte. Originate in thymus from T-cell precursors (prothymocytes)
• make up 2/3rds of lymphocyte population in the blood
• several subsets of T lymphocytes
• have surface T-cell receptors (TCR) – linked to a membrane protein (CD3) – used for recognition of antigen

T helper/inducer/CD4 cells:
• regulatory cells that release lymphokines
• after being primed by the antigen presenting cell presentation of the antigen  stimulate proliferation of other T cells
• help B cells produce antibodies
• carry CD4 marker molecules on surface

T suppressor:
• suppress unwanted antibody production
• mediate destruction of virus infected cells and tumour cells that are recognised as being foreign

T cytotoxic/cytolytic/killer/CD8 cells:
• directly attack and lyse virus infected cells and cancer cells
• specificity of attack is determined by antigens on surface of target cell and specificity of receptor on T cell
• CD8 refers to presence of ‘cell differentiation complex 8’
• ‘T’ refers to thymus, as they mature in thymus

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