Immunoglobulin constant (IgC)-like domain of antigen receptor CD80
Glycoproteins B7-1 (CD80) and B7-2 (CD86) are expressed on antigen-presenting cells and deliver the co-stimulatory signal through CD28 and CTLA-4 (CD152) on T cells. Signalling through CD28 augments the T-cell response, whereas CTLA-4 signalling attenuates it. CD80 contains two Ig-like domains, an amino-terminal immunoglobulin variable (IgV)-like domain characteristic of adhesion molecules and a membrane proximal immunoglobulin constant (IgC)-like domain similar to the constant domains of antigen receptors. Members of the Ig family are components of immunoglobulin, T-cell receptors, CD1 cell surface glycoproteins, secretory glycoproteins A/C, and Major Histocompatibility Complex (MHC) class I/II molecules. In immunoglobulins, each chain is composed of one variable domain (IgV) and one or more IgC domains. These names reflect the fact that the variability in sequences is higher in the variable domain than in the constant domain. The IgV domain is responsible for antigen binding, and the IgC domain is involved in oligomerization and molecular interactions.