Immunoreactivity of two novel monoclonal antibodies against human inducible co-stimulator ligand.

Human inducible co-stimulator ligand (GL50, CD275), also known as B7-H2 or ICOSL, is a positive co-stimulatory molecule of B7/CD28 superfamily, which plays a critical role in immune response. Here we generated two novel mouse anti-human GL50 monoclonal antibodies (MAbs) using classical hybridoma technology. The two MAbs (clones 2B4 and 4D11) were IgG1 (κ) and IgG2a (κ), respectively, and bound specifically to human GL50. Epitope competition assay showed that 2B4 and 4D11 bind to the same epitope of GL50, which is not recognized by the commercially available GL50 MAb (9F-8A4). Functionally, the two MAbs act as a blocker of T cell proliferation. Taken together, as useful tools, these two antibodies might be of great value for further exploration of the immune identification and function of GL50.