Signaling mechanisms in thymocyte selection

The processes known as positive and negative selection that determine the fate of T and B cells depend on finely tuned interactions between the T-cell receptor complex, CD4 or CD8 co-receptors, and a peptide-MHC complex. New work indicates that the avidity of this interaction is critical in the determination of its outcome. The effects of these interactions on developing thymocytes are also a function of the unique activation properties with which thymocytes are programed just before they undergo selection