The UC10-4F10-11 antibody reacts with an extracellular epitope on mouse CD152 (CTLA-4), a type I transmembrane glycoprotein receptor expressed on the surface of activated T and B cells and thymocytes. CD152 comprises a disulfide-linked homodimer of ~35 kDa subunits and is a member of the immunoglobulin protein superfamily. It functions as an antagonistic homolog of CD28 by binding the CD28 co-stimulatory ligands, CD80 and CD86. CD152 thereby acts to inhibit CD28-mediated stimulation during the early stages of T cell expansion. It also contributes to the suppressor function of T regulatory cells. CD152 has important roles in immunological tolerance and immunity, and mutations in its cognate gene have been associated with certain autoimmune disorders.