Selective depletion of activated T cells: the CD40L-specific antibody experience.

Blocking the signal that provides co-stimulation to T cells during their encounter with antigen is thought to make T cells anergic or tolerant. Recently, treatments using CD40L-specific antibody, a co-stimulation blocking reagent, in primate transplant models indicated that this elegant concept could finally be turning into reality. In this context, the finding that CD40L-specific antibody acts through depletion of activated T cells rather than through co-stimulation blockade might seem undesirable. However, the selective removal of cells that are key effectors of immunopathology could provide a powerful tool for containing unwanted immune responses such as those that mediate autoimmune diseases and transplant rejection.