The CD28.2 monoclonal antibody specifically binds to CD28, a 44 kDa homodimeric transmembrane glycoprotein present on most mature T cells, thymocytes and plasma cells. CD28 is a costimulatory receptor that binds CD80 and CD86 as ligands and plays a very important role in T cell-B cell interactions. It has been suggested that CD28 initiates and regulates a separate and distinct signal transduction pathway from those stimulated by the TCR complex. Additionally, it has been reported that CD28 antibody clones vary in their ability to stimulate T cells to produce IL-2 and increase intracellular Ca2+ concentration. This finding suggests the existence of functionally distinct subregions on the CD28 molecule. CD28.2 has been demonstrated to bind to the same molecule as clone L293, another CD28 mAb, and has been reported to induce Ca2+ influx in Jurkat T cells.
This clone also cross-reacts with a subset of peripheral blood lymphocytes, but not monocytes or granulocytes, of baboon, rhesus and cynomolgus macaques. The distribution on lymphocytes is similar to that observed with normal human donor lymphocytes; however, as described in the literature, the frequency of CD28.2-positive lymphocytes is reduced in the non-human primate, with the majority of cells being CD28 negative.