The T cell surface protein, CD28.

The cluster of differentiation (CD) antigen CD28 is a 44-kDa, disulphide-bonded, homodimeric glycoprotein, which is constitutively expressed on the surface of all murine T cells and the majority of human T cells. Ligation of CD28 by its counter receptor, B7, expressed on the surface of antigen presenting cells, has been shown to induce signals that, in synergy with those derived from engagement of the T cell receptor by an antigen bound to a major histocompatibility complex, enhance proliferation and cytokine production. Manipulation of this interaction can have dramatic effects on the outcome of T cell activation. Blocking CD28/B7 interactions may be useful in preventing unwanted activation in allergy and autoimmune diseases, whereas enhancing this interaction can promote tumour rejection. Thus, CD28 and its signalling pathways may prove to be useful targets in the development of new therapeutic treatments.