Modulation of Th1 and Th2 responses for immunotherapy

Abstract

Novel therapeutic agents that differentially modulate immune responses are needed to boost protective immunity against infections and neoplasms and conversely, to suppress inappropriate immune reactions responsible for allergic and autoimmune disorders and the rejection of transplanted organs. One major concept that has guided the search for such agents asserts the existence of at least two types of CD4+ helper T-cells, Th1 and Th2 cells, that differ in their pattern of cytokine production and govern different arms of the immune response. Th1 cells produce IFN-γ, IL-2 and TNF-β and are involved in cell-mediated immune responses that are beneficial in host-defence against intracellular pathogens and malignant cells, but detrimental in mediating autoimmunity. Th2 cells secrete IL-4, IL-5, IL-9, IL-10 and IL-13, which augment antibody responses, including IgE production, and protect against helminth infestations but also cause allergy and asthma. Moreover, Th1 and Th2 responses are mutually antagonistic, such that they normally exist in equilibrium and cross-regulate each other. Alterations of this equilibrium are thought to underlie the etiopathogenesis of many immune-mediated diseases. By selectively targeting either one of these two types of polarised responses, it may therefore, be possible to achieve desired therapeutic effects without broad alterations of the immune system. The various strategies proposed in the patent literature of the last three years to modulate the Th1/Th2 balance are reviewed here. These include procedures that affect the differentiation of Th1 and Th2 cells, their production of effector cytokines and the activity of these cytokines. A profusion of new molecular targets for pharmacologic development has been identified and some attempts at therapeutic manipulation of Th1 and Th2 responses in clinical trials have been encouraging, while others have been disappointing. The emerging notion that Th1 and Th2 responses are themselves controlled by another category of T-cells, called regulatory T-cells, has offered further opportunities for immunotherapeutic intervention in autoimmunity and allergy.

• allergy
• autoimmunity
• cytokines
• immunoregulation
• T-cells
• Th1 cells
• Th2 cells