Interleukin-17 (IL-17) is produced by many subsets of immune cells including neutrophils, macrophages, NKT cells, CD8+ T cells, γδ T cells and Th17 cells, a new subset of CD4+ T lymphocytes. Louis-Marie Charbonnier, Benoit Vokaer and their research team previously observed in vitro that whole CD4+CD25+ containing a majority of foxp3+ regulatory T cells (Tregs) prevented Th1 and Th2 alloreactivity but not Th17 cells and even more seemed to promote them. This raised the possibility of a Th17-mediated alternative pathway of allograft rejection facilitated by Th1 and Th2 downregulation. Herein they investigated the implication of IL-17 in skin allograft rejection across MHC I or II mismatched skin allograft rejection or in case of different CD25+ on CD25- recipient CD4 T cell ratios.
Their preliminary results confirm the upregulation of IL-17 production by high ratio of CD4+CD25+/ CD4+CD25- T cells. Although IL-17 seems not to be critical for conventional MHC-mismatched acute skin allograft rejection, its role in case of suppressed Th1 and Th2 alloreactivity requires further investigations.