CD28 is a glycoprotein and member of the CD28/B7 family of co-stimulatory receptors that promotes T cell activation.{52543} Alternative splicing of CD28 produces one full-length long isoform, CD28 long, and three short isoforms, CD28a, CD28b, and CD28c.{52544} CD28 long exists as a membrane-bound homodimer and contains a leader peptide, an extracellular immunoglobulin variable (IgV) domain that interacts with the co-stimulatory molecules CD80 (Item No. 32013) or CD86 (Item No. 32010) and a cytoplasmic tail that mediates the association with the signal transduction enzyme PI3K and is critical for T cell activation.{52543,52545} CD28a, CD28b, and CD28c contain truncated extracellular or transmembrane domains and exist as soluble monomers (CD28a) or membrane-bound homodimers (CD28b and CD28c).{52544} CD28 is constitutively expressed on the surface of T cells, upregulated by antigen-presenting cells (APCs) displaying MHC-bound antigen, and downregulated after T cell activation.{52546,52547} CD28 competes with CTLA-4 (Item No. 32009), an inhibitor of T cell activation also expressed on T cells, for binding to CD80 or CD86, promoting T cell activation by inducing the production of cytokines, such as IL-2 and IFN-y, and decreasing the T cell receptor activation threshold.{52546} Genetic deletion of CD28 abolishes cellular infiltration and bone erosion in the joints and decreases serum levels of anti-collagen-IgG in a mouse model of collagen-induced arthritis.{52548} CD28 levels are decreased on plasma cells isolated from patients with multiple myeloma and this decrease is associated with disease progression and poor prognosis.{52549} CD28 SNPs have been found in individuals with sporadic breast cancer.{52550} Cayman's CD28 Long Isoform Extracellular Domain (human, recombinant) protein is a disulfide-linked homodimer. The reduced monomer, comprised of CD28 (amino acids 19-152) fused to human IgG1 Fc at its C-terminus, consists of 375 amino acids, has a calculated molecular weight of 42 kDa, and a predicted N-terminus of Asn19 after signal peptide cleavage. As a result of glycosylation, the monomer migrates at approximately 55 to 65 kDa by SDS-PAGE under reducing conditions.
100 ug
Cayman Chemical
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