|| Suppressor T cells (Ts cells) once became probably the most controversial topic in the field of immunology. However, recently the picture has changed dramatically. Suppressor T cells, now less provocatively renamed regulatory T cells (Treg cells) are isolated and can be expanded in vitro and in vivo and their role is the subject of intensive investigation. It is now well recognized that Treg cell is central components of fundamental immune functions such as self-tolerance, anti-tumor response, T cell homeostasis, allergic and autoimmune diseases, allograft transplantation and control of infection. Although regulatory T cells play a crucial role in the control of immune responses to bacteria, fungus, virus and parasites, little is known about the role of Treg cells in mycobacterial infections. Here, I briefly describe 1)the biology of Treg cells, 2)induction and expansion of pathogen-specific Treg cells, 3)beneficial and detrimental roles of Treg cells in infection and 4)“Old Friends” mechanism of hygiene hypothesis. This article also explores observations on Treg or Ts cells in mycobacterial infectious diseases such as leprosy and tuberculosis. I finally summarize the potential for Treg-targeted immunotherapy in infectious diseases allergic and autoimmune diseases as well as transplantation and anti-tumor immunity.
The correct balance of effector/pathogenic and regulatory T cells for successful immunotherapeutic approach is also emphasized.
Key Words : Hygiene hypothesis, Leprosy, Superantigen, Suppressor T cells, Tuberculosis.