UVB and UVC, but not UVA, potently induce the appearance of T6- DR+ antigen-presenting cells in human epidermis.

Non-Langerhans cell, antigen-presenting T6- DR+ epidermal cells (EC) appear 3 days following broad band ultraviolet radiation exposure of human skin and are responsible for the increased antigen presentation capacity of EC seen 3 days after UV exposure. To determine the UV wavelengths that induce T6- DR+ EC, volar forearm skin of 10 human volunteers was irradiated in vivo with 4 minimal erythema doses (MED) each of pure UVA (mean 482 J cm-2), UVB (mean 0.390 J cm-2), and UVC (mean 0.397 J cm-2). The purity of the light sources was as follows: UVB, 98% of the emission was in the UVB range; UVC, 97% of the irradiance was in the UVC range; UVA, 100% of the energy had wavelengths longer than 340 nm. Three days after UV irradiation with 4 MED of each wavelength band, suction blister-derived EC suspensions were prepared from the UV-exposed and unirradiated sites. Percentages of T6+ DR+ Langerhans cells (LC) and T6- DR+ EC were quantitated. Relative to control EC, which contained 2.4 +/- 0.3% T6+ DR+ LC, the mean percentage (+/- SEM) of T6+ DR+ LC contained within UV-exposed EC was significantly decreased as follows: UVB, 0.5 +/- 0.2%; UVC, 0.9 +/- 0.1%; UVA, 0.5 +/- 0.2% (n = 10). T6- DR+ EC, absent in control EC, were induced both by UVB, 5.2 +/- 1.7% and UVC; 1.5 +/- 0.4%. Despite the use of more than 1200 times greater doses in J cm-2 of UVA than UVB and UVC, UVA was a poor inducer of T6- DR+ EC (0.5 +/- 0.2%) and in about half of these individuals, T6- DR+ EC were undetectable. The UV wavelengths for induction of T6- DR+ EC lies predominantly within the UVB band, but also to a lesser extent within the UVC band. These wavelengths appear to be analogous to both the wavelengths for generation of increased host susceptibility to UV-induced murine tumors and to the wavelengths for UV-induced systemic suppression of contact hypersensitivity. However, our data indicate that UV wavelengths for decreasing the number of T6+ DR+ LC in humans differs from the wavelengths for induction of systemic suppression of contact hypersensitivity in mice. Taken together, these data suggest that the appearance of T6- DR+ EC, but not the disappearance of T6+ DR+ LC, following UV exposure may be related to the induction of such antigen-specific suppressor T cells.