The Role of Co-receptors in T Cell Activation

Abstract

Although the expression of the T cell receptor-CD3 complex (TcR-CD3) confers T lymphocyte antigen specificity, several other integral membrane proteins play significant roles during T cell-mediated cellular immune responses (Bierer et al., 1989). By initiating signal transduction events and/or increasing the strength of adhesion between T cells and antigen presenting cells, these cell surface molecules cooperate with the TcR-CD3 complex to initiate biochemical signals that lead to efficient T cell activation and subsequent effector function. By binding their cognate ligands on antigen presenting cells, co-receptor molecules such as CD2, CD4 and CD43 play important roles in T cell adhesion and activation. Each of these molecules, however, contribute uniquely to the T cell response. The expression of these molecules as well as of mutated forms of these receptors in appropriate recipient cell lines has helped document the role of each of these molecules in T cell activation.