agonist CD28 aptamers with immunostimulatory properties in a mouse tumor model, a monoclonal anti-CD28 Fab´ antibody FR104, or an octapeptide AB103, which prevents CD28 homodimerization. Interactions CD28 has been shown to interact with: GRAP2, Grb2, and PIK3R1. See also List of human clusters of differentiation References Further reading External links Mouse CD Antigen Chart Human CD Antigen Chart Clusters of differentiation