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.
Kang
K
K
Department of Dermatology, University of Michigan, Ann Arbor 48109-0530.
Hammerberg
C
C
Meunier
L
L
Cooper
K D
KD
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