The stepwise activation of cytotoxic T lymphocytes.

The recognition of antigen is the first stage of T-lymphocyte maturation in vivo. Monoclonal antibodies directed against the T-cell receptor/CD3 complex and against other surface antigens can also provide this stimulus. Gianni Gromo and his colleagues are attempting to characterize the steps leading from this initial activation to full functional maturation. They suggest that while numerous pathways of activation exist, the particular pathway followed and to what extent activation occurs depend on both the stimulating ligand and its cell surface receptor.