CD28 (C-Term) Rabbit Monoclonal Antibody (RM404)

CD28 is a glycoprotein and member of the CD28/B7 family of co-stimulatory receptors that promotes T cell activation.¹ Alternative splicing of CD28 produces one full-length long isoform, CD28 long, and three short isoforms, CD28a, CD28b, and CD28c.² 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 and a cytoplasmic tail that mediates the association with the signal transduction enzyme PI3K and is critical for T cell activation.^1,3 CD28a, CD28b, and CD28c contain truncated extracellular or transmembrane domains and exist as soluble monomers (CD28a) or membrane-bound homodimers (CD28b and CD28c).² 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.^4,5 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-γ, and decreasing the T cell receptor activation threshold.⁴ 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.⁶ CD28 levels are decreased on plasma cells isolated from patients with multiple myeloma and this decrease is associated with disease progression and poor prognosis.⁷ CD28 SNPs have been found in individuals with sporadic breast cancer.⁸ Cayman’s CD28 (C-Term) Rabbit Monoclonal Antibody (RM404) can be used for immunohistochemistry (IHC) and Western blot (WB) applications.

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1. Esensten, J.H., Helou, Y.A., Chopra, G., et al. CD28 costimulation: from mechanism to therapy. Immunity 44(5), 973-988 (2016).

2. Magistrelli, G., Jeannin, P., Elson, G., et al. Identification of three alternatively spliced variants of human CD28 mRNA. Biochem. Biophys. Res. Commun. 259(1), 34-37 (1999).

3. Stein, P.H., Fraser, J.D., and Weiss, A. The cytoplasmic domain of CD28 is both necessary and sufficient for costimulation of interleukin-2 secretion and association with phosphatidylinositol 3'-kinase. Mol. Cell Biol. 14(5), 3392-3402 (1994).

4. Mak, T.W., and Saunders, M.E. T cell activation. The Immune Response: Basic and Clinical Principles 373-401 (2006).

5. Vallejo, A.N., Brandes, J.C., Weyand, C.M., et al. Modulation of CD28 expression: Distinct regulatory pathways during activation and replicative senescence. J. Immunol. 162(11), 6572-6579 (1999).

6. Tada, Y., Nagasawa, K., Ho, A., et al. CD28-deficient mice are highly resistant to collagen-induced arthritis. J. Immunol. 162(1), 203-208 (1999).

7. Nair, J.R., Calson, L.M., Koorella, C., et al. CD28 expressed on malignant plasma cells induces a prosurvival and immunosuppressive microenvironment. J. Immunol. 187(3), 1243-1253 (2011).

8. Chen, S., Zhang, Q., Shen, L., et al. Investigation of CD28 gene polymorphisms in patients with sporadic breast cancer in a Chinese Han population in northeast China. PLoS One 7(10), (2012).