The monoclonal antibody reacts with human CD28, a 45 kDa costimulatory receptor and a member of the Ig superfamily.
CD28 is expressed by thymocytes, most peripheral T cells, and NK cells. CD28 is a receptor for CD80 (B7-1) and CD86
(B7-2). Signaling through CD28 augments IL-2 and IL-2 receptor expression as well as cytotoxicity of CD3-activated T cells.
The antibody has been shown to stimulate the proliferation of human T cells in vitro.