MCA2839 recognises a chicken orthologue of Inducible T cell co-stimulator ligand (LICOS), a co-stimulatory molecule also known as CD275, GL50, B7-H2, B7RP-1, B7H2, or ICOSL. The interaction of LICOS with its receptor, ICOS (CD278) plays an important role in T-cell co-stimulation, and proliferation, in response to damage and infection. Mammalian LICOS is expressed on B-cells and macrophages and can be up-regulated in response to inflammatory cytokines. This antibody stains a proportion of splenocytes stimulated with CD40 ligand.