T Lymphocytes: Ontogeny, Function, and Relevance to Clinical Disorders

Abstract

T-lymphocytes, unlike B lymphocytes, predominantly recognize antigen when it is associated with membrane-bound products of the major histocompatibility complex (MHC).^{1 2 3} This "dual" recognition (i.e., for both antigen and the MHC) is important for activation of both cytotoxic effector T cells and immunoregulatory T cells. Cytotoxic T cells lyse specific target cells, including tumor cells and cells infected with virus, whereas immunoregulatory T cells act as inducers or suppressors for interactions among T cells, B cells, macrophages, and other cells.The exquisite specificity of T cells has long been thought to be determined by unique, clonally distributed (clonotypic) cell-surface receptors. Because . . .