Infection with respiratory syncytial virus influences FasL-mediated apoptosis of pulmonary γδ T cells in a murine model of allergen sensitization

γδ T Lymphocytes in Asthma: a Complicated Picture

A minor subset (approximately 5%) of peripheral T cells has their TCR build up from γ and δ chains instead of α and β-those are the γδ T lymphocytes. They can be functionally divided into subsets, e.g., Th1-, Th2-, Th9-, Th17-, Tfh-, and Treg-like γδ T cells. They share some specifics of both innate and adaptive immunity, and are capable of rapid response to a range of stimuli, including some viral and bacterial infections. Atopic diseases, including asthma, are one of major health-related problems of modern western societies. Asthma is one of the most common airway diseases, affecting people of all ages and having potential life-threatening consequences. In this paper, we review the current knowledge about the involvement of γδ T cells in the pathogenesis of asthma and its exacerbations. We summarize both the studies performed on human subjects as well as on the murine model of asthma. γδ T cells seem to be involved in the pathogenesis of asthma, different subsets probably perform opposite functions, e.g., symptom-exacerbating Vγ1 and symptom-suppressing Vγ4 in mice model of asthma.

Mutual interplay between IL-17-producing γδT cells and microbiota orchestrates oral mucosal homeostasis

γδT cells are a major component of epithelial tissues and play a role in tissue homeostasis and host defense. γδT cells also reside in the gingiva, an oral tissue covered with specialized epithelium that continuously monitors the challenging dental biofilm. Whereas most research on intraepithelial γδT cells focuses on the skin and intestine epithelia, our knowledge on these cells in the gingiva is still incomplete. In this study, we demonstrate that even though the gingiva develops after birth, the majority of gingival γδT cells are fetal thymus-derived Vγ6+ cells, and to a lesser extent Vγ1+ and Vγ4+ cells. Furthermore, we show that γδT cells are motile and locate preferentially in the epithelium adjacent to the biofilm. Vγ6+ cells represent the major source of IL-17-producing cells in the gingiva. Chimeric mice and parabiosis experiments indicated that the main fraction of gingival γδT cells is radioresistant and tissue-resident, persisting locally independent of circulating γδT cells. Notably, gingival γδT cell homeostasis is regulated by the microbiota as the ratio of Vγ6+ and Vγ4+ cells was reversed in germ-free mice, and their activation state was decreased. As a consequence, conditional ablation of γδT cells results in elevated gingival inflammation and subsequent alterations of oral microbial diversity. Taken together, these findings suggest that oral mucosal homeostasis is shaped by reciprocal interplays between γδT cells and local microbiota.

Role of γδ T cells in exacerbated airway inflammation during reinfection of neonatally primed mice in adulthood

Age at primary infection with respiratory syncytial virus (RSV) is a crucial factor in determining the outcome of reinfection. However, how neonatal RSV infection affects the immune system and renders the host more susceptible to reinfection in later life is poorly understood. In the present study, by using BALB/c mice that were first infected with RSV as neonates, the role of γδ T cells in the development of airway inflammation during reinfection in adulthood was investigated. We found that neonatal RSV infection resulted in an aggravated infiltration of mononuclear cells in bronchoalveolar lavage (BAL) fluids, in parallel with a significant increase in the levels of type 2 cytokines in lungs on day 4 after reinfection. Since the numbers of total γδ T cells as well as activated γδ T cells, particularly IL-4-, IL-5-, and IL-13-producing γδ T cells, were enhanced markedly in the lungs of neonatally primed mice, we speculate that γδ T cells might participate in the augmented airway inflammation seen during reinfection. Indeed, depletion of γδ T cells attenuated the severity of lung histopathology during reinfection. Meanwhile, treatment of neonatal mice with anti-TCRδ mAb diminished not only the numbers of neutrophils, eosinophils, and lymphocytes, but also the levels of IL-4, IL-5, and IL-13 in the lungs after reinfection in adulthood, suggesting that γδ T cells, particularly Th2-type γδ T cells might play a critical role in exacerbating the pulmonary tissue pathology during reinfection of adult mice that were first infected as neonates.