The lymphocyte responsible for cell-mediated immunological reactions, such as graft rejection, and characterized by the possession of T cell receptors (q.v.). T lymphocytes differentiate within the microenvironment of the thymus gland. Mature T cells can be divided into two groups (CD4 and CD8) on the basis of their ability to recognize certain classes of histocompatibility molecules (HCMs). CD4+ cells, which recognize class II HCMs, function as helper T lymphocytes (q.v.). CD8+ cells, which recognize class I HCMs, function as cytotoxic T lymphocytes (q.v.). See histocompatibility molecules, V(D)J recombination. Compare B lymphocyte.
Subjects: Chemistry — Genetics and Genomics.