Structure, function, and serology of the T-cell antigen receptor complex.

The vertebrate immune response involves a complex interplay between different cell types, mediated in part by interacting cell surface structures. Of the cells involved in the immune response, both the B and T lymphocytes have the capacity for specific recognition of a tremendous variety of anti­ gens. Despite this superficial similarity, the processes by which T cells and B cells acquire and carry out their recognition and effector functions differ in several important respects. T cells recognize antigen only on the surface of other cells, and antigens are recognized only in the context of products of the major histocompatibility complex (MHC). The antibody produced by B cells is capable of recognizing antigen both alone and in soluble form. The immunoglobulin molecule serves both recognition and effector functions for the B cell. T cells can be divided into subclasses according to effector function, including cells capable of cytotoxic (Tc) or helper (Th) activity. Each functional class has been demonstrated to employ a distinct set of cellular products in the effector function which can be distinguished from the structure used for antigen recognition. The T-cell antigen recep­ tor, unlike B-cell surface immunoglobulin, is intimately associated with an ensemble of auxiliary proteins that may function in signal transduction.