产品描述： Involved in T-cell activation, the induction of cell proliferation and cytokine production and promotion of T-cell survival. SUBUNIT:

Homodimer; disulfide-linked. Interacts with DUSP14. Binds to CD80/B7-1 and CD86/B7-2/B70. SUBCELLULAR LOCATION:

Membrane; Single-pass type I membrane protein. TISSUE SPECIFICITY: Expressed in T-cells and plasma cells, but not in less

mature B-cells. Human CD28 antigen is a 44 kDa disulfide linked homodimeric T cell specific surface glycoprotein. It is a cell

adhesion molecule of the immunoglobulin superfamily which is constitutively expressed on most peripheral blood T lymphocytes

(approximately 95% of CD4+ cells and 50% of CD8+ cells). Mature thymocytes exhibit higher levels of CD28 than the immature

cells. Activation of T cells results in enhanced CD28 expression. T cell activation requires two combined signals provided by antigen

presenting cells. The first is mediated via the T cell receptor following its interaction with antigenic peptide MHC complexes, and the

second is delivered by accessory or costimulating molecules through their counter receptors on T lymphocytes. CD28 bears structural

homology to CTLA 4 which is expressed at very low levels on the surface of CD4+ and CD8+ peripheral blood cells only following

activation. CD28 is the natural receptor for the B7/BB 1 ligand (CD80) a 55-60 kDa glycoprotein which is expressed on activated B

lymphocytes, on dendritic cells and on interferon gamma treated monocytes. The binding of B7 1/BB 1 molecules to CD28 is involved

in T lymphocyte activation and in the initiation and maintenance of chronic inflammation.