CD28 (human):Fc (human) (rec.) | CHI-HF-210CD28

CD28 and CTLA-4 together with their ligands, CD80 (B7-1) and CD86 (B7-2), constitute one of the dominant
costimulatory pathways that regulate T and B cell responses. CD28 and CTLA-4 are structurally homologous
molecules that are members of the immunoglobulin (Ig) gene superfamily. Both CD28 and CTLA-4 are composed
of a single Ig V-like extracellular domain, a transmembrane domain and an intracellular domain. CD28 and CTLA4 are both expressed on the cell surface as disulfide-linked homodimers or as monomers. The genes encoding
these two molecules are closely linked on human chromosome 2 and mouse chromosome 1. Mouse CD28 is expressed constitutively on virtually 100% of mouse T cells and on developing thymocytes. Cell surface expression
of mouse CD28 is downregulated upon ligation of CD28 in the presence of PMA or PHA. In contrast, CTLA-4 is
not expressed constitutively but is upregulated rapidly following T cell activation and CD28 ligation. Cell surface
expression of mouse CTLA-4 peaks approx.y 48 hours after activation. Although both CTLA-4 and CD28 can
bind to the same ligands, CTLA-4 binds to B7-1 and B7-2 with a 20-100 fold higher affinity than CD28. CD28/B7
interaction has been shown to prevent apoptosis of activated T cells via the upregulation of bcl-XL. CD28 ligation
has also been shown to regulate Th1/Th2 differentiation.

Use / Stability
Stable for at least 1 year after receipt when stored at -20°C. Working aliquots are stable for up to 3 months when stored at -20°C.

Product Specifications

Biological Activity

Measured by its binding ability in a functional ELISA. Immobilized CD28 (human):Fc (human) (rec.) (#CHI-HF-210CD28) at 20μg/ml (50μl/well) can bind the protein CD80 (human):Fc (mouse) (rec.) (#CHI-HF-211CD80). The EC50 is about 0.05μg/ml.

Purity

≥98% (SDS-PAGE)

Formulation

Lyophilized from 0.2μm-filtered solution in PBS.

Reconstitution

Reconstitute at 100μg/ml in sterile PBS.

Endotoxin Content

<0.06EU/μg protein (LAL test; Lonza).