IL-17A as important cytokine in host defense has been analysed intensively and various homologous have been identified. To further gain insight into the functional properties of chicken (gg) IL-17A its expression profile was analysed by intracellular cytokine staining. In splenocytes and peripheral blood mononuclear cells gg IL-17A was detected in subsets of CD4+ T cells and γδ T cells. In contrast the gg IL-17A producing populations in intestinal intraepithelial lymphocytes were characterized as either CD3+CD25+ cells or γδ T cells. Furthermore, using FLAG tagged gg IL-17A, binding to its receptor was demonstrated on the macrophage cell line HD11. In peripheral blood IL-17A binding activity was found on αβ and γδ T cell subsets, monocytes and a distinct population of CD25high cells. Treatment of HD11 cells with gg IL-17A induced IL-6 mRNA expression and nitric oxide production. These results demonstrate the presence of a αβ T helper17 cell subset and IL-17 producing γδ T cells in the chicken.