CD28 Antibody (37.51.1): sc-12727

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T cell proliferation and lymphokine production are triggered by occupation of the TCR by antigen, followed by a costimulatory signal that is delivered by a ligand expressed on antigen presenting cells. The B7-related cell surface proteins CD80 (B7-1) and CD86 (B7-2), expressed on antigen presenting cells, bind the homologous T cell receptors CD28 and CTLA-4 (cytotoxic T lymphocyte-associated protein-4). The dominant co-stimulatory receptor CD28 is expressed on resting T-cells, while CTLA-4 is expressed as a co-inhibitory receptor on activated T-cells, and binds CD80 and CD86 with higher affinity then CD28. SLAM is a novel receptor on T cells that, when engaged, potentiates T cell expansion in a CD28-independent manner. B7, also designated BB1, is another ligand or counterreceptor for CD28 and CTLA-4 that is expressed on the antigen-presenting cell.