CD28 superagonists: mode of action and therapeutic potential.

Some CD28-specific monoclonal antibodies (mAbs) have the surprising property to activate T-cells without the need for TCR ligation. This review summarizes the differences between these "superagonistic" and conventional CD28-specific mAbs with regard to binding specificity and signalling properties. Furthermore, the dramatic effects of in vivo application of CD28 superagonists with regard to the induction of regulatory T-cells and polyclonal T-cell expansion in lymphopenic settings are discussed under the aspect of potential therapeutic applications.