CD45 glycosylation controls T-cell life and death

CD45, an abundant and highly glycosylated cell-surface protein, is a critical regulator of T-cell development. CD45 is differentially glycosylated throughout the life of a T cell, and the glycosylation state of CD45 controls recognition by various binding partners, affects intracellular signaling by the cytoplasmic tyrosine phosphatase domain and modulates the response of the T cell to antigen. Although the importance of CD45 during T-cell development has been established, it is becoming increasingly clear that glycosylation of CD45 is a dynamic process that modifies T-cell survival, activation and immune function. In this review, we address changes that occur in CD45 glycosylation during T-cell development and differentiation, describe carbohydrate-binding proteins that recognize differentially glycosylated forms of CD45, and discuss how differential glycosylation alters the T-cell response to a variety of signals involved in selection, activation and apoptosis.