Mark Robert Hurle

Analysis of CD28 Interactions with Its Cognate Counter-Receptors CD80 and CD86

CD28 serves as a co-signalling molecule for T cell activation through binding to its cognate counter-receptors CD80 and CD86, expressed on antigen presenting cells. This report summarizes studies conducted to determine the regions of CD28 which are involved in its interactions with CD80 and CD86, using site directed mutagenesis, CD28 mAb epitope mapping, receptor based adhesion assays and direct binding of Ig-fusion proteins to cell surface receptors. These studies show that, although the same overall region on CD28 may be involved in the interactions with CD80 and CD86, subtle but important differences distinguish recognition by the two molecules. These findings, along with other observations on the differential pattern of expression and tissue distribution of CD80 and CD86, and induction of differential cytokine profiles by the two counter-receptors, support the contention that these molecules play distinct roles in the regulation of immune responses in vivo.