The D665-CP042 monoclonal antibody is a chimeric version of the original D665 antibody。The variable domain sequences are identical to the original D665but the constant region sequences have been switched from mouse IgG1to mouse IgG2a。The D665-CP042antibody contains no Fc mutations just as the original mouse IgG1antibody does not。The D665-CP042monoclonal antibody reacts with mouse CD28，a45kDa costimulatory receptor and a member of the Ig superfamily。CD28is expressed by thymocytes，most peripheral T cells，and NK cells。CD28 is a receptor for CD80（B7-1）and CD86（B7-2）。Signaling through CD28induces IL-2and IL-2receptor expression and T cell proliferation。The D665 antibody is a CD28 superagonist and is most commonly used to induce the expansion of Treg cellsin vivoin various mouse models of disease。
