The paradigm of Th1 and Th2 cytokines - Its relevance to autoimmunity and allergy

In the past few years, considerable evidence has accumulated to suggest the existence of functionally polarized responses by the CD4(+) T helper (Th)- and the CD8(+) T cytotoxic (Tc)-cell subsets that depend on the cytokines t hey produce. The Th1 and Th2 cellular immune response provide a useful mode l for explaining not only the different types of protection, but also the p athogenic mechanisms of several immunopathological disorders. The factors r esponsible for the polarization of specific immune response into a predomin ant Th1 or Th2 profile have been extensively investigated in mice and human s. Evidence has accumulated from animal models to suggest that Th1-type lym phokines are involved in the genesis of organ-specific autoimmune diseases, such as experimental autoimmune uveitis, experimental allergic encephalomy elitis, or insulin-dependent diabetes mellitus. Accordingly, data so far av ailable in human diseases favor a prevalent Th1 lymphokine profile in targe t organs of patients with organ-specific autoimmunity. By contrast, Th2-cel l predominance was found in the skin of patients with chronic graft-versus host disease, progressive systemic sclerosis, systemic lupus erythematosus and allergic diseases. The Th1/Th2 concept suggests that modulation of rela tive contribution of Th1- or Th2-type cytokines regulate the balance betwee n protection and immunopathology, as well as the development and/or the sev erity of some immunologic disorders, In this review, we have discussed the paradigm of Th1 and Th2 cytokines in relation to autoimmunity and allergy.