Antigen-presenting OKM5+ melanophages appear in human epidermis after ultraviolet radiation

Psoriatic epidermal cells demonstrate increased numbers and function of non-Langerhans antigen-presenting cells

The recent findings that the immunosuppressant cyclosporine A (CsA) improves psoriasis raises the possibility that cellular immune processes play a major role in the pathogenesis of psoriasis. We therefore investigated the phenotype and function of cells within psoriatic epidermis that can play a role in cellular immunologic reactivity. Double fluorescence microscopic studies with monoclonal antibodies of epidermal cells in suspension (EC) and of histologic sections demonstrated that involved psoriatic skin contained a significantly increased number of non-Langerhans cell T6-DR+ EC (4.9 + 2.1%) relative to uninvolved (0.3 +/- 0.1%), p less than 0.01. This non-Langerhans cell population was comprised of DR+ monocytes, DR+ activated T lymphocytes, a few DR+RFD1+ antigen-presenting cells (APC), and DR+ keratinocytes. Langerhans cell (LC) levels in EC suspension were not different between involved and uninvolved psoriatic epidermis. Functional studies demonstrated that involved psoriatic epidermal cells had an increased capacity to induce T-cell activation and proliferation relative to uninvolved EC (p less than 0.04). This increased APC activity was due to the non-LC T6-DR+HLe1+ APC population and not to DR+ keratinocytes. These results demonstrate that involved psoriatic epidermal cells contain both an increased number and function of antigen-presenting cells. The pathogenetic mechanisms in psoriasis may be related to ongoing cellular immune responses in the skin, and the effect of CsA may be mediated through a suppressive effect on the enhanced antigen-presenting cell activity.

T-cell response to purified protein derivative after removal of Langerhans' cells from epidermal cell suspensions containing keratinocytes expressing class II transplantation antigens

In a previous study we observed that human epidermal cell (EC) suspensions containing HLA-DR-expressing keratinocytes showed an amplified T-cell response to purified protein derivative (PPD). To evaluate further the possible immunological importance of class II transplantation antigens on keratinocytes we have compared the T-cell response to PPD in the presence of the following stimulator cells: EC suspensions from normal skin, or EC from tuberculin-reactive skin with or without removal of Langerhans' cells. The proliferation of purified T lymphocytes from peripheral blood in response to PPD in the presence of various concentrations of autologous EC was measured by [3H]thymidine incorporation on day 6. In 3 experiments out of 4 the EC from tuberculin-reactive skin, containing 28-76% HLA-DR-expressing cells as judged by immunocytochemistry (which also revealed fairly numerous HLA-DQ/-DP-expressing keratinocytes and a slight increase in CD36- and CD4- but not CD1-expressing cells), induced a more pronounced T-cell response to PPD than did normal EC. This was not the case in the fourth experiment, in which a small number of HLA-DR-(15%) and few if any HLA-DQ-/-DP-expressing keratinocytes were found. Immunomagnetic removal of CD1-reactive Langerhans' cells from the tuberculin-reactive EC suspensions resulted in a reduction of the T-cell response to PPD, in most cases down to background level (T cells alone + PPD). This study does not support the hypothesis that HLA-DR-expressing keratinocytes can in themselves act as antigen-presenting cells.

Melanophages in inflammatory skin disease demonstrate the surface phenotype of OKM5+ antigen-presenting cells and activated macrophages

Previous studies in our laboratory revealed that ultraviolet light induces the appearance of epidermal melanophages that have potent antigen-presenting ability, that can activate autoreactive T cells, and that exhibit the immunophenotype OKM5+, OKM1-, T6-, and DR+. Therefore we undertook immunophenotyping of melanophages in selected inflammatory mucocutaneous lesions to determine whether the OKM5+, OKM1- phenotype was limited to ultraviolet-induced inflammation or whether the occurrence of melanophages expressing this antigen-presenting cell phenotype was a more generalized phenomenon. Ten of the eleven patients with chronic inflammatory skin lesions demonstrated melanophages expressing the OKM5+, OKM1-, T6-, DR+ immunophenotype. In addition, they often expressed Mo3e, a marker of activated macrophages. In contrast, melanophages of a patient with post-inflammatory hyperpigmentation, although DR+, failed to express OKM5. These results are taken to support an active role for OKM5+, OKM1-, T6-, DR+ melanophages in inflammatory skin disease because these cells demonstrate the phenotype of activated inflammation-producing monocytes and potent antigen-presenting cells.

Photoimmunology: the mechanisms involved in immune modulation by UV radiation

Ultraviolet radiation (UVR) may be the most prevalent agent that man encounters in his environment. As a result, certain biological adaptations take advantage of the beneficial effects of UVR exposure, e.g. the photoactivation steps involved in vitamin D metabolism. In this regard, UVR plays an important role in maintaining our good health; however, it must be noted that UVR is potentially the most harmful naturally occurring agent in our environment. Thus, it appears that several mechanisms have evolved to protect us against the detrimental effects of UVR overexposure. Although epidermal melaninization or "tanning" may be the most obvious example of these processes, we would argue that adoptive mechanisms within the immune system also provide protection against UVR-induced skin damage. It is now known that UVR affects the distribution and functional activities of various immunocompetent cells within the skin, as well as modifying the production of inflammatory and hematopoietically active cytokines. This review will focus on the known mechanisms involved in the immune modulatory effects of UVR and how adoptive immune responses to UVR-induced skin damage contribute to specific pathological processes.

Cellular autoimmunity in psoriasis and lichen planus

The objective of this investigation was to determine whether specific cellular recognition of the epidermis is associated with the human skin diseases, psoriasis and lichen planus. Epidermal cells (EC) obtained from biopsies of involved and uninvolved skin of patients with these diseases were used as stimulators and targets for autologous peripheral blood mononuclear cells (PBMC) in assays of three conventional manifestations of cellular immunity: lymphocyte transformation, leukocyte migration-inhibition and cell-mediated cytotoxicity. Parallel tests were conducted with autologous PBMC as stimulators to ascertain the tissue specificity of the reactions evoked by autologous EC. Similar assays were conducted with EC and PBMC from a large group of normal subjects, and the results were compared to those of the dermatology patients by rigorous statistical analyses. No evidence of lymphocyte-mediated cytotoxicity towards autologous EC was obtained with any of the subject groups, but autologous EC, and to a lesser extent PBMC, of the psoriasis patients, but not of the other two groups, evoked significant lymphocyte transformation. These results were obtained only with patients on Goeckerman therapy, raising the possibility that they were a manifestation of the treatment (topical coal-tar and ultraviolet light irradiation) rather than of the disease, although reasons are presented why this is unlikely. Clearer evidence of disease-associated autoimmunity was obtained in the leukocyte migration-inhibition assays, where autologous EC, and to a lesser extent, PBMC, of the psoriasis patients in general, not just those on Goeckerman therapy, and not those of the lichen planus patients or of the normal subjects, stimulated the release of a leukocyte migration-inhibition factor. These results support the concept of a central role for T-cell mediated autoimmunity in the pathogenesis of psoriasis.

Expression of OKM5 antigen on epidermal cells in mycosis fungoides plaque stage

To characterize and quantitate potential antigen-presenting cell subsets in the epidermis of patients with cutaneous T-cell lymphoma, epidermal cells in suspension were obtained from involved and uninvolved skin. Involved epidermis contained increased numbers of OKT6+HLA-DR+ Langerhans cells and a variable number of OKM5+ epidermal cells (ECs) in all mycosis fungoides (MF) patients tested (N = 14). The OKM5+ EC population from involved epidermis of MF patients were heterogeneous and comprised both OKM5+HLe1- keratinocytes and OKM5+HLe1+ leukocytes. Uninvolved epidermis, in 6 of 14 patients with MF, contained a small number of OKM5+ leukocytes; however, no OKM5+ keratinocytes were detected. Neither OKM5+ leukocytes nor OKM5+ keratinocytes were detected in the epidermis obtained from healthy controls. The increased number of potential antigen-presenting cells, that is, OKT6+HLA-DR+ Langerhans cells and OKM5+HLA-DR+ monocytic leukocytes, in the epidermis of patients with MF may be important for the activation of abnormal T cells contained within the epidermis of these patients. Such activated T cells may release gamma-interferon and induce expression of both HLA-DR and OKM5 antigens on keratinocytes. OKM5+ keratinocytes are present in the epidermis of patients with MF, but not in normal skin, and may thus play a role in the pathogenetic mechanisms of mycosis fungoides by recruitment of immunocompetent cells to the epidermis.

Effects of topical corticosteroid therapy on Langerhans cell antigen presenting function in human skin

We have investigated the mechanisms by which topical corticosteroids modulate cutaneous immune reactions in man. Volunteers applied clobetasone butyrate 0.05% (Eumovate; EV), betamethasone valerate 0.1% (Betnovate; BV), clobetasol propionate 0.05% (Dermovate; DV), and control vehicles twice daily to forearm skin for 7 days. Steroid therapy significantly decreased the number of HLA-DR/T6 (CD1a) positive Langerhans cells (LCs) per mm2 in suction blister-derived epidermal sheets, expressed as a mean percentage of controls, as follows: EV 69.2%; BV 67.3%; DV 37.8%. LC antigen presenting capacity was determined in the allogeneic and autologous epidermal cell-lymphocyte reactions. The LC-dependent allostimulatory capacity of epidermal cells, expressed as a mean percentage of controls, was also significantly reduced by steroid therapy: EV 45.1%; BV 41.9%; DV 23.4%. Following therapy with clobetasol propionate 0.05%, the capacity of epidermal cells to present tetanus toxoid to, and to augment concanavalin A mediated lymphocyte stimulation of, autologous lymphocytes was reduced to 33.6% and 19.7% respectively of controls. Depression of epidermal cell allostimulatory capacity was not the result of a steroid-induced decrease in the production of epidermal cell-derived thymocyte activating factor (ETAF)/interleukin 1 by keratinocytes, since it could not be reversed by addition of exogenous interleukin 1. Indomethacin, added to block any potential prostaglandin synthesis during the culture period, did not restore the allostimulatory capacity of epidermal cells from steroid-treated sites. Addition of epidermal cells from DV-treated sites depressed the capacity of control epidermal cells to stimulate lymphocytes in the allogeneic epidermal-lymphocyte reaction. Our results demonstrate that the anti-inflammatory action of topical corticosteroids in man is associated not only with a reduction in the number of HLA-DR/T6 positive LCs, but also with a marked decrease in Langerhans cell-dependent T lymphocyte activation. The effects of the different steroids on both of these parameters correlated with their potency as determined in the standard occlusive vasoconstrictor assay. Topical corticosteroids are widely used for the treatment of inflammatory skin disorders, and inhibit not only the elicitation phase, but also the induction phase, of allergic contact dermatitis reactions.(ABSTRACT TRUNCATED AT 400 WORDS)

Parallel recovery of epidermal antigen-presenting cell activity and contact hypersensitivity responses in mice exposed to ultraviolet irradiation: the role of a prostaglandin-dependent mechanism

Contact hypersensitivity (CH) responsiveness to 2-4-dinitro-1-fluorobenzene (DNFB) is depressed in mice that are sensitized through skin sites exposed to ultraviolet radiation (UVR). This is partially due to a reduction in antigen-presenting cell (APC) activity within UVR-exposed skin, a condition marked by a decrease in the density of ATPase/Ia-positive epidermal cells. The purpose of this study was to correlate the histological and functional recovery of APC activity in the skin of C3H mice exposed to low-dose (4 X 450 J/m2) or high-dose (1 X 15 kJ/m2) UVR with the normalization of CH responsiveness. Skin biopsy specimens taken at various intervals after UVR exposure revealed a rapid recovery in the density of ATPase/Ia positive cells: about 70% of normal by 3 days, and normal after 5 days. Functional analyses showed that lymph node cells obtained from donors that were sensitized with DNFB 3 days after UVR treatment transferred normal ear-swelling responsiveness to non-primed recipients, thus indicating that APC activity in UVR-exposed skin paralleled the recovery of ATPase/Ia-positive epidermal cells. This suggested that an alternative mechanism causes the persistent depression of CH in mice exposed to UVR. Mice pretreated with indomethacin prior to UVR exposure demonstrated a capacity to elicit CH responses to DNFB, which paralleled the histological and functional recovery of APC in the skin (i.e., normal CH responses were elicited 3 days after exposure to UVR). We conclude from this study that APC activity in the skin recovers rapidly after exposure to UVR, and that a PG-dependent mechanism is responsible for many of the persistent and systemic effects that cause a depression in the CH responsiveness of mice treated with UVR.

Comparison of alloimmunogenicity of Langerhans cells and keratinocytes from mouse epidermis

Among lymphoreticular cells, Langerhans cells and splenic dendritic cells stand alone in their capacity, when hapten-derivatized, to induce vigorous immune responses, irrespective of route of inoculation, including intravenous. We have examined the comparative efficiency of relatively purified populations of Langerhans cells and their epidermal companions, keratinocytes, to induce alloimmunity when injected intravenously into adult mice. It was found that as few as 100 BALB/c Langerhans cells injected intravenously into C3H mice are capable of inducing specific sensitization as evidenced by subsequent accelerated rejection of BALB/c skin grafts. By contrast, 10,000 BALB/c keratinocytes failed to immunize similarly injected C3H recipients. These results emphasize the unparalleled capacity of Langerhans cells to induce sensitization, and they point to Langerhans cells, among cells within the epidermal compartment, as dominant in the alloimmunogenic potential of skin grafts.

Dose response and time course for induction of T6- DR+ human epidermal antigen-presenting cells by in vivo ultraviolet A, B, and C irradiation

In vivo ultraviolet (UV) exposure of human skin abrogates the antigen-presenting function of T6+ DR+ Langerhans cells and induces the appearance of antigen-presenting T6- DR+ epidermal melanophages. UV-exposed epidermal cells containing T6- DR+ epidermal antigen-presenting cells, in contrast to unexposed epidermal cells containing T6+ DR+ Langerhans cells, potently activate autoreactive regulatory T cells in the absence of exogenous antigens. Autoreactive T cells may be important for regulation of other immune responses such as those which occur in photosensitive lupus erythematosus and in immune surveillance of UV-induced skin cancers. It is therefore imperative to determine the factors that govern their appearance in the skin. It was found that UVB and UVC, but not UVA, induced a dose-dependent appearance of T6- DR+ epidermal melanophages. The optimal time of appearance was 2 or 3 days after UVB and UVC exposure. In contrast, UVA was a poor inducer of T6- DR+ cells at all doses and all time points tested. Although UVA was a poor inducer of T6- DR+ epidermal cells, UVA radiation resulted in depletion of T6+ DR+ Langerhans cells from the epidermis, as did UVB and UVC radiation. This differential effect of UV wave bands on the immunocompetent cells in human skin may be related to the greater potential of UVB exposure to induce skin cancers and to exacerbate systemic lupus erythematosus.

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.

Enhancement of Candida albicans killing activity of separated human epidermal cells by ultraviolet radiation

Ultraviolet irradiation enhanced the Candida albicans killing activity of freshly separated human epidermal cells in vitro. The stimulation was dose-dependent and was not due to soluble extracellular factors acting on non-irradiated epidermal cells. The enhancement of the killing activity remained unchanged when epidermal cells were depleted of Langerhans cells. Protein synthesis inhibitors and prostaglandin antagonists abrogated the ultraviolet-induced augmentation of killing activity.

Inflammatory acquired oral hyperpigmentation: association with melanophages demonstrating phenotypic characteristics of antigen presenting cells and activated monocytes

A case of a 30-year-old black woman who developed acute, extensive intraoral hyperpigmentation is reported. Its relationship to previously described entities is discussed. The condition was associated with the presence of melanophages both in the submucosa and in the oral epithelium. The melanophages displayed phenotypic markers of a population of intraepidermal melanophages previously described as potent T cell-activating, antigen presenting cells (T6- DR+ OKM5+ OKM1-) and of activated monocytes (Mo3e+), as well as other monocyte-macrophage markers (Mono 1 and My7). The distinct phenotype of these melanophages suggests that they could play an active role in the promotion of inflammatory disease.