The Role of T Regulatory Cells in Chlamydia trachomatis Genital Infection

Abstract

T cell-mediated immune suppression of adaptive immune responses is important for the homeostatic function of tissues. Compelling evidence has found that the normal immune system produces T cells with a specialized function in immune suppression and this type of T cell is called a regulatory T cell (TRC). There are various types of TRCs with suppressive function. The majority of TRCs express the transcription factor called forkhead box p3 or Foxp3, and play a pivotal role in the maintenance of immune tolerance by preventing autoimmunity and rejection of transplanted tissue [Grazia Roncarolo et al., 2006; Sakaguchi et al., 2008]. Recently TRCs have also been implicated in preventing inflammatory diseases. Extensive evidence has shown that TRCs exacerbate and suppress inflammatory responses in various diseases, including the human multiple sclerosis model, experimental autoimmune encephalomyelitis (EAE) [Farias et al., 2011] and chronic inflammatory bowel disease [Veltkamp et al., 2011]. TRCs also play major roles in regulating immunity to infections of viral, bacterial or parasitic pathogens. TRCs dampen immune response which control pathogen replication. In many instances, these responses increase pathogen survival. Alternatively, TRCs can also limit collateral tissue damage caused by powerful immune responses directed toward microbes [Belkaid & Tarbell, 2009]. However, tumors and microbes commandeer the immune suppressive properties of TRCs to evade host immunity and cause disease. This is especially prominent at mucosal tissues since they are exposed to a plethora of pathogens. In this review, we will introduce the broad category of TRCs with focus on their phenotype, function and role in maintaining mucosal tissues, especially of the genital tract.