Costimulatory signals contribute to immune regulation and homeostasis. CD28, as the best characterized costimulatory molecule, is constitutively expressed by the vast majority of T lymphocytes. Upon interaction with its ligand B7-1 (CD80)/B7-2 (CD86), CD28 mediates signals that promote T lymphocyte differentiation and proliferation, and enhance antibody production of B lymphocytes. T lymphocytes are the central regulator of the anti-tumor adaptive immune response. Lack of costimulatory signals leads to T lymphocyte tolerance and anergy. It has been demonstrated that deficiencies in both CD28 and inducible costimulator (ICOS) pathways result in complete T lymphocyte tolerance in vitro and in vivo.
Chen S, Zhang Q, Shen L, et al. Investigation of CD28 Gene Polymorphisms in Patients with Sporadic Breast Cancer in a Chinese Han Population in Northeast China. Coleman WB, ed. PLoS ONE. 2012;7(10):e48031.