CD86 is the B7-2 costimulatory molecule and a ligand for CD28 and CD152. CD86/B7-2 is an 80kD type I integral membrane protein and a member of the immunoglobulin superfamily of cell surface receptors. Along with CD80/B7-1, CD86 participates in T cell costimulation via interaction with CD28 and CD152/CTLA-4. It is expressed at very low density in normal tissues but is rapidly upregulated on stimulated B cells, monocytes and dendritic cells. Since CD86/B7-2 has rapid kinetics of induction, it is believed to be the major CD28 ligand expressed early in the immune response.1-9