Cytokines and transplantation: Th1/Th2 regulation of the immune response to solid organ transplants in the adult

It has been very tempting to accept the suggestion that the route to rejection or tolerance of organ transplants is determined by T-helper type 1 and type 2 cells, respectively. Much of the data used to support this idea, however, is indirect and therefore cannot be used to imply a causal role for either population as suggested. Recent experiments have been aimed at further expanding knowledge in this area and conclude that the expansion of neither population alone inevitably results in graft damage or tolerance.