Human CellExp™ CD28, Human/ Cynomolgus / Rhesus macaque Recombinant

Human CD28 (Cluster of Differentiation 28) is expressed on the cell surface as a glycosylated, disulfide-linked homodimer. CD28 is the founding member of a subfamily of costimulatory molecules characterized by an extracellular variable immunoglobulin-like domain. Other members of the subfamily include ICOS, CTLA4, PD1, PD1H, and BTLA. CD28 and CTLA4 are highly homologous and compete for the same ligands B7-1 (CD80) and B7-2 (CD86). CD28 is expressed constitutively on almost all human CD4 T cells and approximately 50% of CD8 T cells. CD28 has diverse effects on T cell functions including the induction of cell proliferation and cytokine production and promotion of T-cell survival. Experiments showed that CD28 and CTLA4 have opposing effects on T cell stimulation. CD28 provides an activating signal and CTLA4 provides an inhibitory signal. Translation of a basic understanding of CD28 function into immunomodulatory therapeutics has been uneven, with both successes and failures from pre-clinical studies.