CD28
Description
The CD28 (CD28 molecule) is a protein-coding gene located on chromosome 2.
CD28 (Cluster of Differentiation 28) is a protein expressed on T cells that acts as a co-stimulator, essential for T cell activation and survival. When CD28 is stimulated alongside the T-cell receptor (TCR), it triggers the production of various interleukins, particularly IL-6. CD28 acts as a receptor for CD80 (B7.1) and CD86 (B7.2) proteins, found on antigen-presenting cells (APCs). CD80 expression is upregulated in APCs when activated by Toll-like receptor ligands, while CD86 expression is constitutive. CD28 is the only B7 receptor consistently found on naive T cells. If a naive T cell's TCR interacts with MHC:antigen complex without CD28:B7 interaction, the T cell becomes anergic. CD28 has also been identified on bone marrow stromal cells, plasma cells, neutrophils, and eosinophils, but its function on these cells is not fully understood. It's generally reported that CD28 is present on 50% of CD8+ T cells and over 80% of CD4+ T cells in humans. However, some T cells lose CD28 during activation, and antigen-experienced T cells lacking CD28 can still be reactivated without CD28 engagement.
CD28 is involved in T-cell activation, promoting cell proliferation and cytokine production, and enhancing T-cell survival. It works alongside TCR/CD3 ligation and CD40L costimulation to increase the production of IL4 and IL10 in T-cells. Isoform 3 specifically enhances CD40L-mediated activation of NF-kappa-B and kinases MAPK8 and PAK2 in T-cells.
CD28 is also known as Tp44.
