IL17A and autoimmune disease: More recently, other Th cell sub-groups have been identified, including interleukin-17 (IL-17)-secreting T-cells (Th17 cells) and these cells are also targets for vitamin D. In the autoimmune disease-susceptible non-obese diabetic (NOD) mouse treatment with 1,25D decreased expression of IL-17 (Penna et al., 2006).