IFN-gamma, IL-21 and IL-10 co-expression in evolving autoimmune vitiligo lesions of Smyth line chickens

The Smyth line (SL) of chicken is an excellent animal model for human autoimmune vitiligo. In SL vitiligo (SLV) post-natal loss of melanocytes in feathers appears to be due to cell-mediated immunity. In this study, leukocyte-infiltration and associated expression (RNA) of immune function-related cytokines in growing feathers were investigated throughout SLV-development and -progression. Both leukocyte infiltration and cytokine expression levels started to increase near visible SLV onset (early SLV), reached peak levels during active SLV, and decreased to near pre-vitiligo levels after complete loss of melanocytes. Specifically, significant increases were noticed in relative proportions of T cells, B cells, and MHC II-expressing cells during active SLV. Levels of T cell infiltration were higher than those of B cells, with more CD8+ than CD4+ cells throughout SLV. Elevated leukocyte infiltration in early and active SLV was accompanied by increased levels of cytokine expression, especially in interferon-gamma, interleukin (IL)-10 and IL-21. Low expression of IL-4 and IL-17 did not suggest important roles of Th2 and Th17 cells in SLV pathogenesis. Taken together, SLV appears to be a Th1 polarized autoimmune disease, whereby interferon-gamma expression is strongly associated with parallel increases in IL-10 and IL-21, particularly during early and active stages of SLV.