Description
Information: The inducible costimulator (ICOS, T cell activation molecule H4) is similar to human CD28 (24% homology), and plays an analogous role in the T cell activation process. Unlike CD28, ICOS is only expressed on activated T cells. Secondary signaling through CD28 or ICOS results in discrete cytokine secretion profiles by the activated T cells(1). Engagement of CD152 (CTLA-4) anergizes cells costimulated with either CD28 and ICOS(2). Signaling through ICOS is particularly important in progression of TH2 immune response (5). The receptor for human ICOS is GL50(ICOS L), a member of the B7 family sharing ~20% homology with CD80 (B7-1) and CD86 (B7-2)(3). Two RNA splice variants exist for this molecule, differing only in the cytoplasmic domain(4). Blockade of the ICOS-GL50 interaction in mice improves allograft survival(6) and reduces EAE(7). Recombinant human CD275trn-muIg binds to recombinant and native CD278(ICOS) in EIA and Flow cytometry. Its binding is blocked by pre incubation with soluble recombinant CD278-muIg