[The biological role of UVB-induced cutaneous immunosuppression].

Skin is a large organ which protects our inner body from external stresses. Skin serves not only as a physical barrier but also as an important immune system. Ultraviolet rays B (UVB) activate melanin synthesis by melanocytes in the skin. Melanin, in turn, absorbs UVB and protects the skin from overexposure to UVB. In addition, it is generally known that UVB suppresses immune reaction in the skin. This phenomenon is applied to the treatment of cutaneous diseases such as psoriasis and vitiligo. UVB-induced immunosuppression is mediated by regulatory T cells (Tregs). We and other groups have figured out the mechanism of UVB-induced antigen specific immunosuppression. Here we propose that the role of UVB-mediated immunosuppression is the inhibition of self-destruction against external stresses.