The role of T helper 9(Th9) against Infectious Diseases

Background and aims: Infectious diseases are disorders caused by organisms such as bacteria, viruses, fungi or parasites .The Th9 subset develops in response to combined signals from TGF-b and IL-4 among a cacophony of other cytokines in an extracellular milieu. T helper 9 (Th9) cells,  as a novel CD4 T cell subset, seem to play a complex role in the outcome of specific immune responses. In this article, we aimed to review the role of these cells in infectious disease. Methods: In this mini-review study, we study 25 novel articles since 2009 to 2014 about the role of T helper 9 in some Infectious Diseases. Results: Pleural mesothelial cells promoted Th9 cell differentiation by presenting antigen. It significantly differentiated Th17, but not Th9 cells in the development of CVB3-induced VMC. The microenvironment of VMC seemed to contribute to the differentiation and proliferation of Th17 rather than to differentiation of Th9 cells. Having reviewed the limited number of articles considering this relevance, we came to this result that Lymphatic Filariasis and mycobacterium tuberculosis infections confirmed the existence of such relationship. In addition, Rapamycin resistant murine Th9 cells have a stable in vivo phenotype and inhibit graft-versus-host reactivity but concerning Viral Myocarditis, Th9 cells could not protect against it. Conclusion: The accurate molecular mechanisms underlying the generation and differentiation of human Th9 cells are not elucidated completely. Th9 cells exhibit  Ag specific expansion in a chronic helminth infection (lymphatic filariasis), but in relevance to viral myocarditis, Th9 cells did not play an efficient role against it. However; knowing that whether Th9 cells participate in the protection against infections needs further research.