TGFB1 and Autoimmunity: Moreover, apart from locally increasing levels of potent immunosuppressive cytokines, i.e., transforming growth factor-β1 (TGF-β1) and α-melanocyte stimulating hormone (α-MSH), PNM keratinocytes downregulate MHC class I, Langerhans cells downregulate MHC class II and CD209 expression, while numbers and functions of NK lymphocytes and mast cells in periungual area are also reduced giving the “immune privilege” conditions against autoimmunity (55, 56).