CD11b+ macrophages that infiltrate human epidermis after in vivo ultraviolet exposure potently produce IL-10 and represent the major secretory source of epidermal IL-10 protein.
Because activated human macrophages can be potent sources of IL-10, and because immunosuppressive tolerance-inducing macrophages populate the skin after UV exposure, we determined whether IL-10 is induced after UV exposure of human skin and whether it is related to the immigrating macrophages. Keratomes were obtained from control skin or from skin obtained 72 h after a single exposure to four minimal erythemal doses of UVB. Quantitative reverse-transcriptase PCR on total RNA extracted immediately from skin keratomes showed that IL-10 mRNA was elevated in UV-exposed skin. Epidermal cell suspensions from non-UV-exposed keratomes (C-EC) and UV-exposed keratomes (UV-EC) were fractionated by sequential immunobead selection. IL-10 mRNA was reproducibly 200- to 400-fold higher in CD11b+ UV-EC (macrophages) relative to CD11b- UV-EC (keratinocytes). IL-10 mRNA was not detected in C-EC that contained the CD1a+ population (Langerhans cells) nor in CD1a- C-EC keratinocytes from normal skin. As determined by ELISA, CD11b+ UV-EC IL-10 cell-associated protein was fivefold higher than that of CD11b- UV-EC; this was confirmed by flow cytometric visualization of IL-10 protein in permeabilized cells. CD11b+ UV-EC macrophages secreted IL-10 protein into the supernatant at a level of 333 +/- 51 pg/10(6) cells, whereas UV-EC keratinocytes did not secrete detectable levels of IL-10 (n = 3), although UV did induce low levels of IL-10 mRNA and cell-associated protein in keratinocytes. Therefore, although human keratinocytes accumulate intracellular IL-10 after in vivo UV exposure, the most potent production and secretion of IL-10 in the epidermis seems to be that of UV-induced macrophages. Skin-infiltrating macrophage secretion of such a potent immunoregulatory cytokine may account for the delayed immunosuppressive environment of sunburned skin and the altered APC activity of the infiltrating macrophages.
Department of Dermatology, University of Michigan, Ann Arbor 48109-0530.
K
K
Kang
C
C
Hammerberg
L
L
Meunier
K D
KD
Cooper
D000328:Adult; D004797:Enzyme-Linked Immunosorbent Assay; D004817:Epidermis / Q000276:immunology* / Q000528:radiation effects*; D005434:Flow Cytometry; D006652:Histological Techniques; D006801:Humans; D016753:Interleukin-10 / Q000096:biosynthesis*; D015603:Keratinocytes / Q000276:immunology / Q000528:radiation effects; D007801:Langerhans Cells / Q000276:immunology / Q000528:radiation effects; D016177:Macrophage-1 Antigen / Q000276:immunology; D008264:Macrophages / Q000276:immunology* / Q000528:radiation effects*; D016133:Polymerase Chain Reaction; D013471:Sunburn / Q000276:immunology; D014466:Ultraviolet Rays / Q000009:adverse effects; D015854:Up-Regulation
D016177:Macrophage-1 Antigen; D016753:Interleukin-10