title: Low expression of CD40 and B7 on macrophages infiltrating UV-exposed human skin; role in IL-2Ralpha-T cell activation.
abstract: After UV exposure of skin, epidermal Langerhans cells (LC) are depleted, whereas CD11b+CD36 CD1a- monocytes/macrophages (UV-Mphi) infiltrate. Different immunological outcomes in vivo are mediated by LC (sensitization) and UV-Mphi (tolerance) which may be related to the distinct T cell activation states that these antigen-presenting cells (APC) induce. We previously demonstrated that CD4+ T lymphocytes activated by UV-Mphi are, in contrast to LC-activated T cells, IL-2Ralpha deficient, and we hypothesize that this differential T cell activation is related to differences in co-stimulatory molecules between UV-Mphi and LC. Using four-color flow cytometry, we found a reduced capacity to up-regulate expression of the important co-stimulatory molecules CD40, B7-1 and B7-2 by UV-Mphi relative to LC. This alteration in co-stimulatory molecule expression was selective, because UV-Mphi express equal levels of ICAM-1 and ICAM-3, and increased levels of LFA-1, relative to LC. After bidirectional signaling with T cells during alloantigen presentation, UV-Mphi still exhibited less CD40 and B7-1 than LC. Addition of IFN-gamma induced CD40 and B7-1 expression on UV-Mphi and restored IL-2Ralpha expression on UV-Mphi-activated T cells but had no effect on IL-2Ralpha on resting or LC-activated T cells. The restoration of IL-2Ralpha expression on UV-Mphi-activated T cells by IFN-gamma was inhibited (67 %, p = 0.005) by addition of neutralizing anti-CD40. Therefore, differences in co-stimulatory molecule expression, in particular CD40, on UV-Mphi and LC are critical in determining the distinct T cell activation induced by these APC.
authors.affiliation: Department of Dermatology, Case Western Reserve University, Cleveland 44106, USA. ibk@po.cwru.edu
authors.forename: I B
authors.initials: IB
authors.lastname: Kremer
authors.forename: K D
authors.initials: KD
authors.lastname: Cooper
authors.forename: M B
authors.initials: MB
authors.lastname: Teunissen
authors.forename: S R
authors.initials: SR
authors.lastname: Stevens
mesh_terms: D018122:B7-1 Antigen / Q000096:biosynthesis / Q000276:immunology; D019013:CD40 Antigens / Q000096:biosynthesis / Q000276:immunology; D002465:Cell Movement / Q000276:immunology; D005434:Flow Cytometry; D006801:Humans; D008213:Lymphocyte Activation; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology*; D015375:Receptors, Interleukin-2 / Q000276:immunology*; D012867:Skin / Q000276:immunology* / Q000528:radiation effects*; D013601:T-Lymphocytes / Q000276:immunology*; D014466:Ultraviolet Rays
chemical_list: D018122:B7-1 Antigen; D019013:CD40 Antigens; D015375:Receptors, Interleukin-2