T-HELPER CELL SUBSETS - POSSIBLE IMPLICATIONS IN IMMUNOTHERAPY

Helper T cells bearing CD4 surface receptor molecules (CD4+ T-H cells) are active in both humoral and cell-mediated immune responses. The 2 effector arms of the immune system act in coordination to control infections; one arm or the other usually predominates, depending on the nature of the infectious agent. Such a polarisation in the response is associated with different patterns of cytokine secretion. Type 1 T-H cells (T(H)1), which produce interferon-gamma, preferentially develop during infections by intracellular parasites. Type 2 T-H cells (T(H)2), which produce interleukin (IL)-4, IL-5 and IL-10, predominate during helminthic infestations. T(H)1 and T(H)2 not only provide different modalities of protection against exogenous offending agents, but are also responsible for several pathophysiological conditions. T(H)1 responses are pathogenic in organ-specific autoimmune disorders, contact hypersensitivity and acute allograft rejection. T(H)2-type responses are involved in the pathogenesis of allergic disorders and systemic lupus erythematosus, and are probably responsible for reduced resistance to several infectious agents, including human immunodeficiency virus. The fact that the two T cell subsets are counter-regulatory suggests immunotherapeutic strategies and new approaches to vaccine development.