Human CD28 protein, ECD (extracellular domain), Fc-fusion, recombinant

Description :
CD28 is a single-pass type I transmembrane glycoprotein that belongs to the CD28/CTLA4 (cytotoxic T lymphocyte-associated antigen 4, also known as CD152) family of the immunoglobulin (Ig) superfamily. CD28 and CTLA-4 are structurally homologous molecules and both contain one Ig-like V-type domain in the extracellular region. CD28 and CTLA4 are expressed on the cell surface as disulfide­linked homodimers or as monomers. Together with their ligands, CD80 and CD86, they constitute one of the dominant co-stimulatory pathways that regulate T and B cell responses. CD28 is expressed in T-cells and plasma cells, but not in less mature B-cells. CD28 is involved in T-cell activation, the induction of cell proliferation and cytokine production and promotion of T-cell survival. CD28 is expressed constitutively on nearly all mouse T cells and surface expression is down­regulated upon ligation of CD28. CTLA­4 is not constitutively expressed but is up­regulated rapidly following T cell activation and CD28 ligation. The binding of CD80 and CD86 to its receptor CD28 induces T-cell proliferation and cytokine production. CD28 ligation has also been shown to regulate Th1/Th2 differentiation. CTLA4 binds to CD80 and CD86 with a 20-100 fold higher affinity than CD28 and is involved in the downregulation of the immune response. The CD80/CD86/CD28/CTLA4 pathway can positively and negatively regulate immune responses. CD28 is thus regarded as a promising therapeutic target for autoimmune diseases and cancer.