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

UVB-induced suppression of the mixed epidermal cell lymphocyte reaction is critically dependent on irradiance

The mixed epidermal cell lymphocyte reaction (MECLR) is a commonly used method to study the effects of ultraviolet B (UVB) radiation on the skin immune system. In UVB experiments dosimetry is very important. The influence of irradiance on the MECLR was studied in vitro using Philips FS40 lamps with variable UV intensities. Irradiation of isolated epidermal cells with high irradiance impaired the alloactivating capacity more than irradiation with low irradiance. In vivo, the influence of long-term UVB exposure on the MECLR was studied by treating normal healthy volunteers with suberythemagenic doses of UVB thrice weekly during 4 weeks. The first set of experiments, using low irradiance Sylvania UV-21 F75/85 W lamps, resulted in a decrease of MECLR responses of 83.1%. In the second set of experiments performed a year later, employing an identical protocol except for the use of high irradiance Waldmann UV-21 F85/100 W lamps, an increase of MECLR responses of 99.7% was observed. Volunteers of both sets of experiments received equal doses of UVB. In conclusion, this study shows that in vitro UVB-induced suppression of the MECLR is critically dependent on irradiance and therefore might explain contradictory results described in the literature. The in vivo data suggest that, comparable to the in vitro experiments, irradiance may influence the effects of UVB irradiation in vivo. Further experiments should prove whether this is indeed the case.

Modulation of immunity by ultraviolet radiation: key effects on antigen presentation

In addition to being the major cause of non-melanoma skin cancer, the ultraviolet radiation (UVR) present in sunlight is a potent immunosuppressive agent. Indeed, studies with mice and humans have indicated that the immune suppression induced by UVR is a risk factor for skin cancer development. These observations gave rise to the discipline of photoimmunology, which studies the interaction of electromagnetic radiation, primarily UVB (280-320 nm) light, with the immune system. The focus of this paper will be to review recent studies designed to unravel the mechanisms through which UVR suppresses immune reactivity. Particular emphasis is placed on the effects of UVR on antigen presentation.

Human Langerhans cells express E-cadherin

Murine Langerhans cells (LC) synthesize and express E-cadherin, a Ca(++)-dependent homophilic cell adhesion molecule that mediates LC-keratinocyte (KC) binding in vitro. In vivo, E-cadherin expression by LC may promote localization and persistence of LC within the epidermis through LC-KC adhesion. In addition, changes in LC E-cadherin expression or affinity may be an important factor in the egress of LC from the epidermis after exposure to antigen. The aim of the present study was to determine if human LC also express E-cadherin. Suction blister roofs were obtained from normal volunteers and epidermal cell (EC) suspensions were prepared by limited trypsinization in the presence of 1 mM Ca++. EC were then incubated with antibodies to E-cadherin and CD1a or HLA-DR, and examined by two-color analytical flow cytometry or immunofluorescence microscopy. Most (82.9% +/- 7.4% [mean +/- SD], range 67-89%, n = 7) freshly prepared human LC expressed E-cadherin, as did the majority of KC. The amount of E-cadherin (as determined by mean fluorescence intensity) expressed by LC and KC was similar. Trypsin/EDTA treatment of freshly prepared EC abrogated expression of E-cadherin by LC and KC, whereas E-cadherin was not degraded by trypsin in the presence of Ca++. LC expressed lower levels of E-cadherin after 3 d in culture. Thus, human LC, like murine LC, express the homophilic adhesion molecule E-cadherin, which may be important in establishing and maintaining interactions between LC and KC in mammalian epidermis.

Suppressive and enhancing effects of ultraviolet B radiation on expression of contact hypersensitivity in man

Ultraviolet B (UVB) radiation has multiple effects on the immune system, and these effects contribute to the development of UVB-induced skin cancers in mice, and probably man. Depending upon dose and duration of UVB exposure, the resultant immune aberrations may be strictly local (at the irradiated skin site) or systemic. One important local effect of acute, low-dose UVB regimens is impaired induction of contact hypersensitivity (CH). Because a significant proportion of humans who develop CH when hapten is painted on UVB-exposed skin fall to display a primary allergic reaction at that site, we inquired into the effects of UVB radiation on the expression of CH in man. A high proportion of individuals who were first exposed to a sensitizing dose of hapten via UVB-exposed skin displayed CH when challenged on unirradiated (normal) skin 11 d later. However, only 50% of these subjects developed CH when challenged simultaneously on skin that had been exposed to UVB radiation 11 d previously. Because the density of epidermal antigen-presenting cells was comparable in both responders and non-responders, we interpret these findings to mean that UVB radiation can create a sustained immunosuppressive microenvironment that inhibits the expression of CH. In separate experiments, when normal volunteers were sensitized with hapten via unirradiated (normal) skin, expression of CH at UVB-exposed challenge sites 11 d later was found to be enhanced, at least in some individuals, compared to expression of CH at unirradiated challenge sites. Thus, the local effects of UVB radiation on expression of CH in man may be enhancing or inhibitory, depending upon whether initial sensitization occurred through normal or through UVB-exposed skin.

Cumulative effects from repeated exposures to suberythemal doses of UVB and UVA in human skin

BACKGROUND

The skin is repeatedly exposed to solar UV radiation. Long-term photodamage is a consequence of cumulative UV radiation injury. Hence an examination of the repetitive effects of UV exposure is more likely to yield clues to the early alterations that lead to photoaged skin than a single exposure.

OBJECTIVE

We examined the effects of repetitive low-dose UV irradiation on human skin with the aim of identifying UVA-induced effects that may have a different wavelength dependence than acute erythema.

METHODS

Areas on the lower part of the back were each exposed to a suberythemal dose (0.5 minimal erythema dose [MED]) of solar simulated radiation (290 to 400 nm) and of UVA (320 to 400 nm) once daily, 5 days a week, for 28 doses. One site was also treated daily with a sunscreen having a sun protection factor of 22 and then exposed to 11 MEDs of solar simulated radiation for the same duration. Epidermal and dermal changes were analyzed and quantified by histochemical stains in combination with computer-assisted image analysis of tissue sections.

RESULTS

At equal 0.5 MED doses, UVA induced greater cumulative changes than solar simulated radiation, as assessed by development of a greater cumulative erythema response in the first week of treatment, the presence of epidermal hyperplasia and stratum corneum thickening, depletion of Langerhans cells, dermal inflammatory infiltrates, and deposition of lysozyme on elastin fibers. These changes were not prevented by the sunscreen. A single short-term dose of UVA did not elicit these changes.

CONCLUSION

These findings suggest that UVA may contribute significantly to long-term actinic damage and that the spectral dependence for cumulative damage does not parallel the action spectrum for acute injury (erythema) in human beings.

Extraction and quantitation of cytokine mRNA from human epidermal blister roofs

The demonstration of cytokine mRNA expression in epidermal cells by the polymerase chain reaction technique preceded by reverse transcription (RT-PCR) requires linear test conditions (i.e. that the product obtained after amplification reflects the relative amounts of starting material) and high reproducibility, specificity, and sensitivity. By combining well-defined techniques for mRNA extraction and concentration measurement with a sensitive and well-calibrated RT-PCR technique, we demonstrated the presence of IL-1 alpha, IL-1 beta, IL-6, and TNF alpha in epidermal cells obtained from suction blister roofs from normal volunteers. Messenger RNA was extracted with superparamagnetic oligo(dT)25 Dynabeads, and the amount of mRNA was measured by spectrophotometry using a Beckman 5-microliters Ultra-Microcell prior to RT-PCR. Linear PCR conditions were obtained by carefully titrating the amounts of mRNA and the number of cycles. Reproducibility was estimated at different steps of the procedure, and the specificity of the enhanced cDNA products was verified by liquid hybridization with end-labelled probes. We suggest that this combination of techniques might prove useful for the simultaneous assessment of the expression of various cytokines from small samples of fresh human epidermal cells.

Evidence that regression in keratoacanthoma is immunologically mediated: a comparison with squamous cell carcinoma

Recent research observations suggest that the keratoacanthoma (KA) is a form of resolving squamous cell carcinoma (SCC). The mechanism by which this resolution takes place has not been fully explored, although it may have an immunological basis. To investigate this, we compared 15 clinically and histologically diagnosed KAs and 15 SCCs with regard to cellular infiltrate and keratin expression. We found that KAs have significantly higher numbers of CD3+ and CD4+ cells invading their epidermal component than SCCs. The T lymphocytes infiltrating KAs were more immunologically active, as greater numbers expressed the interleukin-2 receptor (IL-2R) than those in SCCs. It is of interest that CD36 was expressed by a significantly greater proportion of tumour cells within KAs than SCCs. This was also the case for the intercellular adhesion molecule ICAM-1, and the differentiation marker keratin 10. Overall, these findings suggest that KA regression is immunologically mediated, with activated (IL-2R+) CD4+ T lymphocytes and adhesion molecules playing a pivotal role in the immune response.

CD36(+)-dendritic epidermal cells: a putative actor in the cutaneous immune system

In the present study we have investigated by indirect immunofluorescence staining and mixed lymphocyte reaction methods, the localization, distribution, percentage, and the immunological involvement of CD36(+)-dendritic epidermal cells (CD36(+)-DECs) in normal human skin. Human epidermal cell suspensions were obtained from skin specimen of healthy persons. First, an indirect immunofluorescent staining method was performed on frozen skin sections, freshly isolated cells, nonadherent and adherent cells and second, the allogeneic mixed epidermal cell-lymphocyte reaction (ELR) method was performed with human peripheral blood mononuclear cells and irradiated CD36(+)-DECs plus CD-1a+ (Langerhans cells) and/ConA (at 10 micrograms/mL). We found that CD36(+)-DECs were localized in the epidermis mainly in the basal layer. They were non adherent cells. The percentage of these CD36(+)-DECs was of about 2%. These CD36(+)-DECs were AE3 (which recognizes keratin normally expressed by keratinocytes) positive cells. Our immunoreactivity study using allogeneic mixed ELR, showed that CD36(+)-DECs stimulated allogeneic lymphocyte proliferation. Their stimulatory effects were important when Langerhans cells and ConA were added separately or together to the PBMCs culture. The above results suggest that CD36(+)-DECs may contribute to the immunological role of skin and could be involved in cutaneous allograft recognition and rejection.

ABBREVIATIONS

DECs: dendritic epidermal cells; ConA: concanavalin A; DPM: disintegrations per minute; ELR: epidermal cell-lymphocyte reaction; LC: Langerhans cells; PBMCs: peripheral blood mononuclear cells.

Antigen-presenting capacity in normal human dermis is mainly subserved by CD1a+ cells

A proposed role for antigen-presenting dermal dendrocytes in the pathogenesis of many dermal inflammatory skin diseases remains speculative. We therefore sought to determine the phenotype and functional characteristics of antigen-presenting cells isolated from normal human dermis. Normal adult human skin was incubated overnight with dispase at 4 degrees C, the epidermis was removed, and the residual dermal preparation was then minced and digested with a mixture of hyaluronidase, collagenase, and DNAase at 37 degrees C, prior to filtration through mesh. Dermal cell suspensions thus obtained were stained using specific monoclonal antibodies, and analysed by fluorescence microscopy or flow cytometry. Mean values were as follows: CD45+ leucocytes 39%, HLA-DR+ cells 39%, Ulex europaeus agglutinin I+ endothelial cells 26%, CD1a+ cells 3.9%, CD11b+ cells 16%, CD11c+ cells 6%. Mitomycin C-treated crude dermal cell suspensions induced allostimulation of peripheral blood mononuclear cells in a 7-day culture, as assessed by 3H-TdR incorporation. Depletion of CD1a+ Langerhans-like cells from the dermal cell preparation, by 95, 74 and 90% in three separate experiments using immunomagnetic beads, reduced 3H-TdR incorporation at optimal responder-to-stimulator cell ratios by 90, 64, and 87%, respectively. Our findings suggest that, in normal human dermis, the great majority of the alloantigen-presenting capacity resides in the CD1a+ Langerhans cell-like dendritic antigen-presenting cell population, and not to any great extent in either CD1a- macrophage-like cells, or HLA-DR+ endothelial cells. The relationship of the CD1a+ dermal antigen-presenting cells to the Langerhans cell lineage remains to be determined.

Dendritic cells in cutaneous lupus erythematosus: a clue to the pathogenesis of lesions

In view of the critical role of dendritic cells in immune mediated skin diseases, we have investigated the membrane antigen patterns and ultrastructure of cutaneous dendritic cells in eight patients with chronic discoid lupus erythematosus and five with subacute cutaneous lupus erythematosus. In the lesional epidermis, the expression of HLA-DR antigens by epidermal dendritic cells was reduced, as compared with perilesional, clinically normal skin. In addition, only few CD1a+ dendritic cells (Langerhans' cells), along with some CD11c+ and CD14+ cells (presumable precursors of Langerhans' cells), were found in atrophic areas of lesional epidermis. In contrast, the number of Langerhans' cells in non-atrophic areas of lesional epidermis was similar to that in perilesional skin. On electronmicroscopy, epidermal Langerhans' cells appeared depleted of organelles and dendrites and contained tubuloreticular inclusions. In the lesional dermis, both CD1a+ and CD36+ dendritic cells were found, associated with CD4+ and CD8+ T-cells, respectively. Moreover, CD11c+ and CD14+ cells were found around capillaries in the papillary dermis on electronmicroscopy. Indeterminate cells (dendritic cells with features of Langerhans' cell lineage, but apparently without Birbeck granules) and dendritic macrophages were found, associated with lymphocytes and mast cells. No cells with intermediate/transitional features between these two dendritic cell types were found. Conversely, peculiar dendritic cells--with short and blunt dendrites and cytoplasm containing many flat, rough cisternae, moderately well developed Golgi apparatus and no lysosomes--were found in the same location as the CD11c+ and CD14+ cells identified by light microscopy. These findings might be interpreted as follows: 1 the alterations in cytological differentiation and expression of functionally meaningful molecules by epidermal Langerhans' cells in cutaneous lupus erythematosus lesions suggest an impairment of their immunological efficiency; 2 in the lesional dermis of cutaneous lupus erythematosus, a CD4+ T-cell/CD1a+ dendritic cell-based, delayed-type immune response is possibly modulated by a suppressor T-cell circuit in which CD36+ dendritic cells may act as accessory cells; 3 CD11c+ and CD14+ cells with peculiar ultrastructure are possible precursors of both CD1a+ indeterminate cells and CD36+ dermal dendrocytes in the dermis.

Relationship between the ability of sunscreens containing 2-ethylhexyl-4'-methoxycinnamate to protect against UVR-induced inflammation, depletion of epidermal Langerhans (Ia+) cells and suppression of alloactivating capacity of murine skin in vivo

The UVB sunscreen 2-ethylhexyl-4'-methoxycinnamate was evaluated in hairless albino mouse skin for its ability to inhibit UVR-induced (i) oedema, (ii) epidermal Langerhans cell (Ia+) depletion and (iii) suppression of the alloactivating capacity of epidermal cells (mixed epidermal cell-lymphocyte reaction, MECLR). The sunscreen, prepared at 9% in ethanol or a cosmetic lotion, was applied prior to UVB/UVA irradiation. In some experiments there was a second application halfway through the irradiation. Single applications in both vehicles gave varying degrees of protection from oedema and Langerhans cell depletion but afforded no protection from suppression of MECLR. When the sunscreens were applied twice there was improved protection from oedema and Langerhans cell depletion and complete protection was afforded from suppression of MECLR. There was a clear linear relationship between Langerhans cell numbers and oedema with and without sunscreen application. The relationship between Langerhans cell numbers and MECLR was more complex. These data confirm published discrepancies between protection from oedema (a model for human erythema) and endpoints with immunological significance, but show that 2-ethylhexyl-4'-methoxycinnamate can afford complete immunoprotection, although protection is dependent on the application rate and vehicle.

Atopic dermatitis: recent trends in pathogenesis and therapy

Emerging concepts in the areas related to the pathogenesis and treatment of atopic dermatitis are reviewed. In particular, recent findings have revealed several key steps in the maintenance of a vicious circle of spongiotic dermatitis associated with elevated T-lymphocyte activation, hyperstimulatory Langerhans cells, defective cell-mediated immunity, and B-cell IgE overproduction. The discovery of specific IgE-binding structures on Langerhans cells provides a mechanism for Langerhans cells to capture and present IgE-targeted allergens to allergen-specific T cells. Furthermore, certain microbial allergens that tend to preferentially elicit IgE-type responses also elicit a T-cell response dominated by the IgE-inducing lymphokine interleukin 4. Repeated stimulation by activated Langerhans cells appears to induce just such a response. Abnormal biochemical responsiveness and mediator release by AD monocytes, mast cells, and eosinophils also participate in the sustainment or initiation of such a vicious circle, and contribute directly to the dermatitis as well. Developments in the areas of neuropeptides, genetics, microbial superantigens, and cytokine networks in the skin also appear to have promise in providing a rational link between immune defects and the inflammatory events in AD. Conventional therapy remains the mainstay of atopic dermatitis management; however, new therapies based upon the above concepts are being tested in clinical trials. Although the difficulty of objectively grading AD lesional activity and the high placebo response of AD patients hampers the interpretation of many reports, several types of approaches are coming into focus. The effectiveness of cyclosporin A, which targets T-cell activation and antigen presentation, indicates that additional agents with such activity should be effective, and verifies the criticality of these cells in AD pathogenesis. Therapy with biologic response modifiers, such as interferon gamma or thymopentin, is oriented toward normalization of imbalanced immune responsiveness, rather than direct suppression of the immune system. The mechanism of action of and toxicities of Chinese herbal mixtures require further investigation, but may reveal hitherto unconsidered avenues. Other recent therapeutic trials have focused on reduction of trigger factors, such as house dust mite exposure, foods, and the abnormal epidermal lipid barrier to irritation.

Melanocytes freshly isolated from normal human skin express the cell membrane receptor for the adhesive glycoprotein thrombospondin

Thrombospondin (TSP) is an adhesive protein with multiple binding sites, which is able to mediate several cell-to-cell and cell-to-matrix interactions, particularly through its cell membrane receptor (TSP-R). Because human keratinocytes are able to synthesize and express TSP, and as TSP is also localized at the dermal-epidermal junction in normal human skin, we questioned whether epidermal cells are able to bind available TSP, that is, to express TSP-R. To investigate this, we employed gold immunoelectron microscopy on epidermal cells freshly isolated from normal human skin; the TSP-R was detected by OKM5 monoclonal antibody. Epidermal cells showing ultrastructural characteristics of melanocytes were gold-stained on their plasma membrane, whereas keratinocytes, Langerhans cells and lymphocytes were unstained. Although functional studies are clearly necessary to clarify the role(s) played by the TSP-R on the cell surface of melanocytes, it is tempting to speculate that the TSP-R may be important for melanocyte adhesion to the dermal-epidermal junction and to keratinocytes. Such adhesion may not only subserve the steric localization of melanocytes, but also have important implications for those functional activities of melanocytes which have been shown to require close contact between these cells and adjacent keratinocytes and/or basement membrane components.

Expression of intercellular adhesion molecule-1 (ICAM-1) and OKM5 in UVA- and UVB-induced lesions in patients with lupus erythematosus and polymorphous light eruption

Pathological skin reactions were induced with both UVA and UVB in 12 patients with lupus erythematosus (LE) and with UVA in 7 with polymorphous light eruption (PMLE) but in none of the controls. Biopsy specimens taken from UV-induced lesions showed that in dermal infiltrates of LE cases CD4-positive cells predominated, whereas in the majority of PMLE cases CD8-positive cells predominated. Keratinocytes expressed intercellular adhesion molecule-1 (ICAM-1) in 7 of the 12 UVA- and in eight of the ten UVB-induced LE lesions, and in three of the UVA-induced lesions of PMLE patients. Three different staining patterns were found. In subacute cutaneous LE (SCLE) cases staining throughout the epidermis resembled that seen in genuine SCLE lesions. In discoid LE (DLE) lesions, the staining was most prominent in and near the basal cell layer. In the one systemic LE case and in the PMLE cases, ICAM-1 expression was seen only in association with epidermal spongiosis and T-cell infiltration. Keratinocytes did not express ICAM-1 in the controls or in the non-irradiated skin of the LE patients. In five on the UVA-induced lesions, in eight of the UVB-induced LE lesions and in one of the PMLE cases, keratinocytes expressed CD36. In four of the six LE lesions with fewer CD1a-positive cells, dendritic CD36-positive cells were seen in the epidermis. In conclusion, the pattern of activated keratinocytes and immunocompetent cells in the dermis was similar to that seen in genuine LE and PMLE lesions, but dissimilar to each other and to the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies of contact hypersensitivity induction in mice with optimal sensitizing doses of hapten

To avoid unsuspected and unwanted consequences of excess hapten during epicutaneous sensitization, optimal sensitizing doses of dinitrofluorobenzene (DNFB) were determined for several ultraviolet B radiation (UVB)-resistant and UVB-susceptible strains of mice. Using these doses of hapten applied epicutaneously or injected intracutaneously into normal or UVB-exposed body wall skin, it was determined that four consecutive daily exposures to UVB prevented contact hypersensitivity induction in all mice when optimal sensitizing doses of DNFB were applied epicutaneously. By contrast, UVB-resistant, but not UVB-susceptible, mice developed contact hypersensitivity when an optimal sensitizing dose of DNFB was injected intracutaneously into UVB-irradiated skin. Moreover, whereas UVB-susceptible mice failed to develop contact hypersensitivity when an optimal sensitizing dose of DNFB was painted on skin exposed to a single dose of UVB, UVB-resistant mice did develop contact hypersensitivity under similar circumstances. Based on these results, it is concluded that 1) conventional doses of epicutaneously applied haptens induce contact hypersensitivity with the aid of antigen-presenting cells derived from both the epidermis and the dermis, 2) the phenomenon of UVB susceptibility is mediated by cells and molecules within the dermis when conventional doses of hapten and UVB radiation are employed, and 3) UVB susceptibility is mediated by cells and molecules within the epidermis when optimal sensitizing doses of hapten and a single exposure to UVB are employed.

Neutrophils, differentiated macrophages, and monocyte/macrophage antigen presenting cells infiltrate murine epidermis after UV injury

We asked whether, as in humans, a population of antigen-presenting macrophages infiltrates the epidermis of ultraviolet (UV)-exposed BALB/c mice. Using three-color flow cytometry on cell suspensions plus in situ immunofluorescence microscopy, the phenotype of normal Langerhans cells was class II major histocompatibility complex (MHC+), CD11b+, NLDC-145+, BM8+ CD45+ and homogeneous. By contrast, in epidermal cells harvested 3 d following UV (UV-EC), there were two subsets of class II MHC+ cells: 1) class II MHChi CD11b+, and 2) class II MHClo CD11b-. Neither expressed the Langerhans cell markers BM8 and NLDC-145. In addition, there were two major populations of class II MHC- CD11b+ cells; half of these expressed the GR-1 neutrophil marker. Langerhans and dendritic epidermal T cells were markedly reduced after UV injury. By electron microscopy, immunomagnetic bead-purified CD11b+ cells in UV-EC were comprised of neutrophils, differentiated macrophages, and mononuclear cells with prominent lysosomes, but no Birbeck granules; the class II MHC+ subset resembled a monocytic cell in between differentiated macrophages and indeterminate dendritic cells. Functionally, immediately following in vivo UV exposure, the allogeneic antigen-presenting cell capacity of UV-EC was reduced to 21 +/- 6% of control epidermal cells (C-EC); by 3 d, antigen-presenting cell activity of UV-EC had recovered to 59 +/- 11% of C-EC, although at this time NLDC-145+ Langerhans cells had reached their lowest number. The recovered antigen-presenting cell activity was critically dependent upon the class II MHChiCD11b+ cells. Sensitization of BALB/c mice through skin that contained these antigen-presenting cells (3 d after UV) resulted in tolerance to dinitrofluorobenzene. By contrast, sensitization through UV-exposed skin immediately after the exposure resulted in unresponsiveness without tolerance, demonstrating temporal association of tolerance with leukocytic infiltration. In summary, murine epidermis responds to an acute UV injury in vivo with an initial abrogation of antigen-presenting activity followed by epidermal infiltration with neutrophils, differentiated macrophages, and monocytic antigen-presenting cells that are distinct from Langerhans cells with regard to expression of Langerhans cell markers and ultrastructure.

Effects of acute, low-dose UVB radiation on the induction of contact hypersensitivity to diphenylcyclopropenone in man

Healthy volunteers (n = 14, age range 20-31 years, mean 23) were irradiated on the inside of the left forearm on four consecutive days with their individual minimal erythemal dose of ultraviolet B (UVB) prior to sensitization in the same skin area with a 2% solution of diphenylcyclopropenone (DPCP). The reaction patterns were compared with 14 alopecia areata patients (age range 16-69 years, mean 40) starting topical immunotherapy with DPCP, sensitized without prior UVB treatment. Primary allergic reactions occurred in ten volunteers and in four alopecia areata patients. Patch testing on the upper back with serial dilutions of DPCP (1% to 10(-8)%) showed minimal dermatitis-eliciting concentrations ranging from 1 to 10(-4)% (mean 0.19%) in the volunteers as compared with 10(-1) to 10(-8)% (mean 0.025%) in the alopecia areata patients. Two patterns were discernible within the volunteers with respect to the intensity of the primary allergic and elicitation reactions. Ten volunteers reacted in a similar way to the alopecia areata patients, whereas four probands demonstrated very high minimal dermatitis-eliciting concentrations and overall less severe reactions. The DPCP-specific T-cell response using blood macrophages and B lymphocytes as antigen-presenting cells was measured in an in vitro assay in two alopecia areata patients and two volunteers having similar skin reactions as well as in two volunteers with overall less severe skin reactions. B lymphocytes from the alopecia areata patients and the volunteers with similar skin reactions induced a significant DPCP-specific T-cell proliferation exceeding the responses obtained using macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)

UV exposure reduces immunization rates and promotes tolerance to epicutaneous antigens in humans: relationship to dose, CD1a-DR+ epidermal macrophage induction, and Langerhans cell depletion

Increasing UVB radiation at the earth's surface might have adverse effects on in vivo immunologic responses in humans. We prospectively randomized subjects to test whether epicutaneous immunization is altered by prior administration of biologically equalized doses of UV radiation. Multiple doses of antigens on upper inner arm skin (UV protected) were used to elicit contact sensitivity responses, which were quantitated by measuring increases in skin thickness. If a dose of UVB sufficient to induce redness (erythemagenic) was administered to the immunization site prior to sensitization with dinitrochlorobenzene (DNCB), we noted a marked reduction in the degree of sensitization (P less than 0.0006) that was highly dose responsive (r = 0.98). Even suberythemagenic UV (less than a visible sunburn) resulted in a decreased frequency of strongly positive responses (32%) as compared to controls (73%) (P = 0.019). The rate of immunologic tolerance to DNCB (active suppression of a subsequent repeat immunization) in the groups that were initially sensitized on skin receiving erythemagenic doses of UV was 31% (P = 0.0003). In addition, a localized moderate sunburn appeared to modulate immunization with diphenylcyclopropenone through a distant, unirradiated site (41% weak responses) as compared to the control group (9%) (P = 0.05). Monitoring antigen presenting cell content in the epidermis revealed that erythemagenic regimens induced CD1a-DR+ macrophages and depleted Langerhans cells. In conclusion, relevant and even subclinical levels of UV exposure have significant down modulatory effects on the ability of humans to generate a T-cell-mediated response to antigens introduced through irradiated skin.

Cultured human Langerhans cells process and present intact protein antigens

Epidermal Langerhans cells (LC) undergo profound phenotypic and functional alterations when cultured for 2 to 3 d. To determine whether the in vitro culture of human LC modulates their capacity to process and present intact protein antigens, we compared the ability of freshly isolated LC (fLC) and cultured LC (cLC) to stimulate in vitro T-cell proliferative responses to recall antigens. We found that human fLC and cLC were able to process and present recall antigens to primed T cells, inducing significant proliferative responses. For tetanus toxoid and Candida albicans extract, T-cell proliferative responses at 6 d to antigen-pulsed fLC were slightly greater than responses to antigen-pulsed cLC. For live influenza A virus, the T-cell responses induced by antigen-pulsed cLC were comparable or slightly greater compared with fLC. Allogeneic T-cell proliferation for both LC preparations were also comparable. The exogenous pathway of antigen processing was demonstrated by chloroquine inhibition.

Effect of topical sunscreens on the UV-radiation-induced suppression of the alloactivating capacity in human skin in vivo

Exposure of mice or humans to solar or artificial ultraviolet radiation (UV) has been shown to induce a number of changes in the immune system that may influence their susceptibility to skin tumors. The protective effect of sunscreens on these changes is not clear. Thirty-two patients with a variety of dermatoses routinely undergoing treatment with standard UVB (n = 19) or PUVA (n = 13) therapy were studied. One of the two tested sunscreens or its vehicle was applied to the right flexor forearm immediately prior to each total-body UV exposure. Epidermal sheets were obtained by the suction-blister method from the left flexor forearm before treatment and from both flexor forearms after 4 weeks of photo- or photochemotherapy and used as stimulator epidermal cells (EC) in the mixed epidermal cell-lymphocyte reaction (MECLR). After 4 weeks of either UVB or PUVA therapy the MECLR responses on EC from both arms were markedly decreased. Neither the tested sunscreens nor their vehicles prevented the UV-induced suppression of the alloactivating capacity. The failure of sunscreens to protect against the UV-induced suppression of the alloactivating capacity could be explained in two ways. First, the energy not absorbed by the sunscreen could be sufficient to induce suppression of the alloactivating capacity. An alternative explanation could be systemic immune suppression by UV. In order to discriminate between these possibilities only the right forearms of 10 healthy volunteers, treated with a sunscreen or its vehicle, were irradiated with UVB during 4 weeks. In this manner systemic immune suppression by UVB could be excluded. This experiment resulted in a similar suppression of the MECLR responses, as induced by total body UVB irradiation, without any protection by the sunscreen. Apparently, the UV dose not absorbed by the sunscreen was capable to induce suppression of the alloactivating capacity. Our results indicate that people protected from sunburn by sunscreens may be exposed to UV for a long period of time, and thereby subject themselves to its immunosuppressive action.

CD36(OKM5)+ dendritic cells in the oral mucosa of HIV- and HIV+ subjects

In this study, we have investigated by light and electron microscopy the presence, distribution, and inner structure of CD36(OKM5)+ dendritic cells (DC) in the lamina propria and epithelium of the oral mucosa of HIV- and HIV+ subjects; in the latter, both clinically healthy areas and areas of hairy leukoplakia (HL) were studied. Perivascular CD36+ DC were present in the lamina propria of all the specimens studied. They were also found in small numbers in the epithelium of clinically healthy mucosa of HIV- and HIV+ subjects, but were practically absent from the epithelium of HL. CD36+ DC seemed to be regularly HLA-DR+ in HIV-subjects; this positivity was recognized only in some cells in the clinically healthy mucosa of HIV+ subjects, and practically never in HL. Because the only perivascular cells observed in the clinically healthy areas of HIV+ subjects were CD36+, we investigated the ultrastructure of perivascular DC in these same areas. These cells were characterized by the presence of a prominent Golgi apparatus, many lysosomes, and focal adhesions to the extracellular matrix. It may be concluded that 1) CD36+ DC are physiologic components of the oral mucosa, 2) they share some ultrastructural features with macrophages, 3) no differences in numbers were found between HIV+ and HIV- subjects, and 4) these cells are affected in their expression of HLA-DR antigens during HIV infection, particularly in areas of HL. This may be a hint that the antigen-presenting function of these cells in the oral mucosa is negatively affected during HIV infection.

Regional development of Langerhans cells and formation of Birbeck granules in human embryonic and fetal skin

The regional development of Langerhans cells (LC) and the formation of Birbeck granules (BG) were examined in human embryonic and fetal skin. Samples were obtained from multiple anatomic sites and stained with anti-CD36, anti-CD1a, and anti-HLA-DR antibody as well as Lag antibody specifically reactive to BG and some vacuoles of human LC. In the first trimester, CD36+ dendritic epidermal cells were identified before the appearance of CD1a+ cells and Lag+ cells. Some of the former co-expressed HLA-DR antigens but not CD1a antigens. In the second trimester, regional variations in LC development were observed. Epidermal LC of palms and soles reached a peak in number in the first trimester but were rarely detected after 18 weeks estimated gestation age (EGA), whereas, in other regions, their number increased with age. In the second trimester, CD1a+ cells and Lag+ cells were also identified in the epidermis, although Lag+ cells appeared later than CD1a+ cells. The Lag+ cells until 17 weeks EGA showed a variety of staining intensities and immunoelectron microscopy revealed that they contained various amounts of Lag-reactive BG. Flow cytometric analysis showed that relative amounts of Lag antigens in LC increased during the second trimester and that fetal LC of 18 weeks EGA expressed the same amounts of HLA-DR, CD1a, and Lag antigens as did adult human LC. In the dermis, in the second trimester, numerous CD36+ cells and HLA-DR+ cells were found, whereas CD1a+ cells and Lag+ cells were rarely detected. Taken together, it is suggested that HLA-DR+ dendritic cells acquire CD1a+ antigens first and then form BG after migration to the epidermis and that fetal LC are phenotypically mature in the second trimester.

Dermal dendrocytes and photochemotherapy

We studied the fate of dermal dendrocytes in patients treated with psoralens and ultraviolet light by combining immunohistochemistry and computerized image analysis. Factor-XIIIa-positive dermal dendrocytes were found to be altered in these patients. When compared with controls, dermal dendrocytes were often increased in number and had an uneven size and tissue distribution. Their cytoplasm was occasionally fragmented. These changes were more pronounced when early photosclerosis was present. The alterations described probably reflect vascular changes, and may be responsible for immunomodulating actions and disorder of the connective tissue structure induced by ultraviolet light.

Keratinocyte expression of CD36 antigen in benign and malignant epidermal cell-derived tumours

Keratinocytes express the macrophage/monocyte antigen CD36 in a variety of inflammatory cutaneous diseases characterised by a T lymphocyte rich infiltrate. Since cell-mediated immune mechanisms also play a role in host responses to skin tumours, we investigated the presence of CD36 antigen on keratinocytes in a range of epidermal cell-derived benign and malignant tumours characterised by a peritumoural, dermal lymphocytic infiltrate. Frozen tissue sections of lesional tissue from a range of epidermally derived tumours were labelled with antibodies to CD1a, CD11b, CD36, and HLA-DR antigens. Benign and malignant squamoproliferative tumour cells exhibited a spectrum of CD36 expression, whereas those of basal cell origin were consistently CD36-. Suprabasal expression of CD36 was present in the normal perilesional epidermis of all tumours studied including basal cell carcinoma. Keratinocyte CD11b expression was not observed. The widespread presence of keratinocyte CD36 positivity in squamoproliferative, but not basal epidermal, tumours suggests its expression may be linked to the degree of keratinocyte differentiation. The stimulus for expression is unknown, but the fact that suprabasal perilesional epidermis expressed CD36 strongly in the absence of infiltrate suggests it may represent a non-specific response by keratinocytes to various stimuli.

Immune sensitization against epidermal antigens in polymorphous light eruption

To get further insight into the pathogenesis of polymorphous light eruption, we studied nine patients with polymorphous light eruption and six healthy persons. Two skin biopsy specimens were obtained from each person, one from previously ultraviolet light-irradiated skin and another one from unirradiated skin. An epidermal cell suspension, skin homogenate, or both were prepared from each specimen. Autologous cultures were made with peripheral blood mononuclear cells combined with irradiated or unirradiated skin homogenate and peripheral blood mononuclear cells combined with irradiated or unirradiated epidermal cell suspension. Cell proliferation was assessed by 3H-thymidine incorporation assay. The response of peripheral blood mononuclear cells to unirradiated epidermal cells or unirradiated skin homogenate was similar in both patients and controls. However, peripheral blood mononuclear cells from patients with polymorphous light eruption showed a significantly increased proliferative response to both irradiated epidermal cells and irradiated skin homogenate. Our results indicate that ultraviolet light increases the stimulatory capability of polymorphous light eruption epidermal cells in a unidirectional mixed culture with autologous peripheral blood mononuclear cells. This suggests that an immune sensitization against autologous ultraviolet light-modified skin antigens occurs in polymorphous light eruption.

Lymphocytic infiltrates of the skin in association with cyclosporine therapy

Three patients, one of whom has been previously reported, had erythematous papules and nodules of the face and upper part of the chest during cyclosporine therapy for inflammatory skin diseases. Histologic examination and DNA analysis (performed in two cases) revealed benign dermal lymphocytic infiltrates. In two cases proliferation of only T cells occurred. In the third case, both T and B cell populations were expanded and there was vacuolar degeneration of the basal layer of the epidermis and IgG, IgM, and C3 deposition along the dermoepidermal junction. These findings may be the result of cyclosporine-induced immune dysregulation. The lesions resolved in all patients after therapy was stopped.

Interactions of epidermal cells and T cells in inflammatory skin diseases

Multiple cell types and their factors and cytokines are involved in regulating the immune response in inflammatory skin diseases. Stimulatory and inhibitory factors interact to determine whether the immune response is regulated up or down. Normally, stimulatory signals are counteracted by inhibitory signals to prevent an immune reaction from being initiated. However, exogenous antigens and irritants or endogenous factors and altered immunogenic self-peptides can upset this balance. When that occurs, T cells are activated and an inflammatory skin reaction develops. Lymphokines released from such activated T cells can modify the phenotype and function of normal keratinocytes. They can induce the expression of adhesion molecules and receptors involved in antigen presentation. Furthermore, they can also stimulate keratinocyte proliferation. This may be important in development of the hyperplasia seen in inflammatory skin diseases, especially in psoriasis. Cytokines released from the activated keratinocytes can both stimulate and attract T cells to the epidermis and thereby continue the ongoing immune reaction.

Ultraviolet radiation can either suppress or induce expression of intercellular adhesion molecule 1 (ICAM-1) on the surface of cultured human keratinocytes

Interactions of the ligand/receptor pair LFA-1(CD11a/CD18) and ICAM-1(CD54) initiate and control the cell-cell interactions of leukocytes and interactions of leukocytes with parenchymal cells in all phases of the immune response. Induction of the intercellular adhesion molecule 1 (ICAM-1) on the surface of epidermal keratinocytes has been proposed as an important regulator of contact-dependent aspects of cutaneous inflammation. Ultraviolet radiation (UVR) also modifies cutaneous inflammation, producing both up- and down-regulation of contact hypersensitivity. We have found that UVR has a biphasic effect on the induction of keratinocyte CD54. Using immunofluorescence and FACS techniques to quantitate cell-surface CD54 staining, we have shown that UVR (100 mJ/cm2 of UVB) significantly (p less than 0.01) inhibits keratinocyte CD54 induction by gamma interferon 24 h after irradiation. However, at 48, 72, and 96 h after UVR (10 to 100 mJ/cm2), CD54 expression is significantly induced (p less than 0.01 to p less than 0.001) to levels even greater than are induced by gamma interferon (20 U/ml). In addition, at 48, 72, or 96 h following UVR (30-100 mJ/cm2), the gamma-interferon-induced CD54 expression on human keratinocytes is also strongly (p less than 0.05 to p less than 0.001) enhanced. In this cell-culture system, gamma interferon and TNF-alpha are both strong CD54 inducers and are synergistic, but GM-CSF, TFG-beta, and IL-1 have no direct CD54-inducing effects. Thus the effects of UVR on CD54 induction are biphasic, producing inhibition at 24 h and induction at 48, 72, and 96 h. This effect on CD54 may contribute to the biphasic effects of UVR on delayed hypersensitivity in vivo. The early inhibition of ICAM-1 by UVR may also contribute to the therapeutic effects of UVR. We also speculate that the late induction of ICAM-1 by UVR might be an important step in the induction of photosensitive diseases such as lupus erythematosus.

Phenotype, ultrastructure, and function of CD1+DR+ epidermal cells that express CD36 (OKM5) in cutaneous T-cell lymphoma

This study investigated the phenotype and function of different antigen-presenting cells (APC) present within the epidermis of patients with cutaneous T-cell lymphoma (CTCL). Involved epidermis of CTCL compared with uninvolved was found to contain increased numbers of CD1+DR+ APC. This population was heterogeneous and comprised both leucocytes of a novel CD1+DR+CD36 (OKM5)+ phenotype and CD1+DR+CD36- indeterminate/Langerhans cells. The CD1+DR+CD36+ leucocytes did not express TcR-1, CD5, CD15, or CD22, and only a minor population expressed CD11, demonstrating that they were neither T nor B cells, and did not belong to the major CD11+ (OKM1+) blood monocyte population. Electron microscopy of purified CD36+ lesional epidermal cells (EC) demonstrated that they lacked Birbeck granules found on CD1(+)-selected Langerhans cells, and most cells exhibited features of indeterminate cells or macrophages. The capacity of EC from involved epidermis to present alloantigens was found to be increased relative to uninvolved epidermis in all patients tested, and this capacity was critically dependent upon the presence of CD45+DR+ bone marrow-derived cells but not on the presence of CD45-DR+ keratinocytes. Positive selection using MoAb against CD1 and CD36 demonstrated that both cell populations exhibited the capacity to stimulate T cells. The results indicate that a novel antigen-presenting cell population with a unique phenotype is present within involved skin of patients with mycosis fungoides. These cells express CD36 in addition to CD1 and have an ultrastructural appearance consistent with a dendritic antigen-presenting cell derivation.

Organization of the monocyte/macrophage system of normal human skin

Monocytes and macrophages are known to be important for a variety of functions; however, whereas epidermal Langerhans cells have been studied in great detail, few data are available for the dermal monocyte/macrophage system. Therefore we investigated the density, distribution, and phenotype of dermal macrophages in normal human skin using a panel of monoclonal antibodies for single and double labeling. We demonstrate here that within normal human dermis macrophages reside with a remarkable density. Principally, these cells exhibit the phenotype of the phagocytic macrophage system (CD11c+, KiM8+), whereas members of the immune phagocyte system (CD11c+, KiM8-) are absent from normal dermis with the exception of a few Langerhans cells in the papillary body. Within the dermal phagocytic macrophage system we uncover an unexpected phenotypical and morphologic heterogeneity, which correlates with the tissue localization. This study provides a basis for investigating the participation and change of the dermal macrophage system in cutaneous disorders.

Immunohistochemical comparison of actinic reticuloid with allergic contact dermatitis

Biopsy specimens of chronic lesions and ultraviolet-induced lesions from actinic reticuloid patients were examined by immunoperoxidase techniques and compared with those of allergic contact dermatitis skin, one of the delayed-type hypersensitivity conditions. Each lesion of actinic reticuloid showed a clear predominance of suppressor/cytotoxic T cells to helper/inducer T cells and an increase of Langerhans cells in the epidermis and the dermis. These findings are generally similar to those in the late phase (on day 7 and 11) but not in the early phase (on day 2) of allergic contact dermatitis and suggest that delayed-type hypersensitivity might be involved in some parts of the pathogenesis of actinic reticuloid. CD36+DR+ epidermal cells were also observed in ultraviolet-induced lesions from actinic reticuloid patients, suggesting a possible role in the modulation of the mechanism.

Antigen presentation and T-cell activation in epidermodysplasia verruciformis

Aberrant immune responses may play a role in the susceptibility of patients with epidermodysplasia verruciformis to human papilloma virus (HPV). We examined the stimulatory capacity of antigen-presenting cells from HPV-infected skin and peripheral blood T-cell responses of patients with epidermodysplasia verruciformis. The percentage of Langerhans cells in relation to total epidermal cells in suspension was slightly reduced in HPV-infected lesions, relative to apparently clinically uninfected epidermis. In addition, the morphologic appearance of Langerhans cells was altered in lesional epidermal sheets. Despite these abnormalities, Langerhans cells were functionally intact in their capacity to present alloantigens to T cells and, in fact, the epidermis of HPV-infected lesions demonstrated enhanced antigen-presenting activity in three of four patients tested. The antigen-presenting activity was entirely abrogated by removal of Langerhans cells and was not associated with increased activity of cytokines with stimulatory activity for the thymocyte co-stimulation assay. Although epidermodysplasia verruciformis T cells were unresponsive to autologous HPV-infected epidermis, they responded well to mitogens, allogeneic mononuclear leukocytes, and allogeneic epidermal cells. Epidermodysplasia verruciformis T cells were inhibited in their capacity to respond to allogeneic epidermal cells when they were simultaneously exposed to autologous epidermal cells from HPV-infected lesional epidermis, but not to normal-appearing epidermis. Thus, although Langerhans cell activity is intact in epidermodysplasia verruciformis, these individuals fail to respond to autologous papillomas, which may, at least in part, be explained by an interaction between papillomal epidermal cells and autologous T cells that results in an inhibited response.

Cutaneous T-cell lymphoma lesional epidermal cells activate autologous CD4+ T lymphocytes: involvement of both CD1+OKM5+ and CD1+OKM5- antigen-presenting cells

Cutaneous T-cell lymphoma is characterized by infiltration of the skin by activated CD4+ T lymphocytes. The mechanism by which these T lymphocytes achieve and maintain their activated state is unknown. Antigen-specific activation of T lymphocytes is dependent upon antigen-presenting cells which express HLA-DR class II major histocompatibility complex molecules, such as epidermal Langerhans cells. In addition to CD1+DR+ Langerhans cells, cutaneous T-cell lymphoma lesional epidermis contains major histocompatibility complex class II positive non-Langerhans cell populations, including CD1+OKM5+ bone-marrow-derived cells and DR+ keratinocytes. We asked whether any of these epidermal cell populations demonstrate capacity to activate T lymphocytes. Various numbers of epidermal cells from uninvolved and involved cutaneous T-cell lymphoma plaques were therefore used to stimulate autologous CD4+ and CD8+ T lymphocytes in the absence of exogenous antigen. Involved epidermal cells potently induced proliferation of CD4+ T lymphocytes (S.I. +/- SEM = 466 +/- 45). In contrast, uninvolved epidermal cells only induced background levels of proliferation (S.I. +/- SEM = 2 +/- 0.5, N = 8, p less than 0.01). Neither involved nor uninvolved epidermal cells were able directly to activate CD8+ lymphocytes. The capability of involved epidermal cells to activate CD4+ T lymphocytes was dependent upon CD1+DR+ leukocytes and not DR+ keratinocytes, because depletion of either HLA-DR+, CD1+ or HLe1+ epidermal cells totally abrogated the T-lymphocyte proliferation. Interestingly, on a cell per cell basis CD1+DR+ cells obtained from involved skin, demonstrated relative to CD1+DR+ cells from uninvolved skin, enhanced capacity to activate CD4+ T lymphocytes. Furthermore, CD1+OKM5+ cells from involved epidermis stimulated autologous CD4+ T lymphocytes. This indicates that a unique hitherto undescribed CD1+OKM5+ epidermal antigen-presenting cell population may participate in T-lymphocyte activation. These findings provide support for the concept that the epidermal cells in cutaneous T-cell lymphoma patients, particularly the antigen-presenting cells, may contribute significantly to the activation of CD4+ malignant and/or non-malignant inflammatory T lymphocytes within the skin.

Cutaneous dermal Ia+ cells are capable of initiating delayed type hypersensitivity responses

The presence of Langerhans cells (LC) within the epidermis has been shown to be critical for inducing T-cell-mediated immune responses in the skin. The purpose of this study was to assess whether cells in the dermis can initiate T-cell-mediated delayed-type hypersensitivity responses in vivo. Initially, back skins from C3H mice were trypsinized to remove the epidermis. The dermis was enzymatically dispersed and filtered to obtain a cell suspension. However, dermal cells exposed to trypsin were contaminated with numerous disaggregated hair follicles. These hair follicles contained Ia+ cells (presumably LC), and upon haptenation in vitro with trinitrophenyl, initiated contact hypersensitivity reactions in vivo. We therefore used dispase in place of trypsin to prevent follicular disaggregation and to allow preparation of dermal cell suspensions free of hair follicles. These hair follicle-free dermal cells were haptenated with trinitrophenyl and injected intradermally. Elicitation of contact hypersensitivity by epicutaneous painting 6 d later revealed the mean +/- SEM incremental ear-swelling response to be 53 +/- 8 mm X 10(-3). In contrast, mice sensitized by injection with dermal cells depleted of Ia+ cells demonstrated only 10 +/- 1 mm X 10(-3) of ear swelling. Thus, like dendritic LC of the epidermis, perivascular dendritic Ia+ cells of the dermis are capable of initiating T-cell-mediated contact hypersensitivity in vivo and may be highly relevant for presentation of antigen to T cells trafficking through the dermis.

UVB radiation and human monocyte accessory function: differential effects on pre-mitotic events in T-cell activation

Purified T lymphocytes fail to proliferate in response to antigenic and mitogenic stimuli when cultured in the presence of accessory cells that have been exposed in vitro to sublethal doses of UVB radiation. Because proliferation represents a final stage in the T-cell activation process, the present study was conducted to determine whether T cells were able to progress through any of the pre-mitotic stages when UVB-irradiated monocytes were used as model accessory cells. In these experiments, monoclonal anti-CD3 antibodies were employed as the mitogenic stimulus. Culture of T cells with UVB-irradiated monocytes did allow the T cells to undergo an increase in intracellular free calcium, which is one of the first steps in the activation sequence. The T cells expressed interleukin-2 receptors, although at a reduced level. However, T cells failed to produce interleukin-2 above background levels when they were placed in culture with monocytes exposed to UVB doses as low as 50 J/m2. Incubation of T cells with UVB-irradiated monocytes did not affect the subsequent capacity of T cells to proliferate, since they developed a normal proliferative response in secondary culture when restimulated with anti-CD3 antibodies and unirradiated monocytes. These studies indicate that T lymphocytes become partially activated when cultured with UVB-irradiated monocytes and mitogenic anti-CD3 monoclonal antibodies. In addition, they suggest that interleukin-2 production is the T-cell activation step most sensitive to inhibition when UVB-irradiated monocytes are employed as accessory cells.

Oral cyclosporine for the treatment of alopecia areata. A clinical and immunohistochemical analysis

Cyclosporine inhibits the activation of helper T cells that may be pathogenic in alopecia areata. Therefore we treated six patients with alopecia areata (five men, one woman) with oral cyclosporine, 6 mg/kg/day for 12 weeks. Three patients had alopecia universalis, one had alopecia totalis, and two had patchy alopecia areata of the scalp. Hair regrowth in the scalp of all patients occurred within the second and fourth weeks of therapy, followed by hair regrowth of the face and chest (in the male patients), pubic area, extremities, and axillae. Overall, the site of best response was the scalp. Cosmetically acceptable terminal hair regrowth on the scalp occurred in three of six patients. Significant hair loss, however, occurred in all patients within 3 months of discontinuation of cyclosporine treatment. Clinical response correlated with changes in immune cell infiltration of the hair follicles. The number of leukocytes per hair follicle was quantified in transverse scalp biopsy sections stained with a panel of monoclonal antibodies. The degree of terminal hair regrowth correlated significantly with decreases in follicular epithelial human lymphocyte antigen-DR and intercellular adhesion molecule-1 expression, T cells, helper/inducer (CD4) T cells, suppressor/cytotoxic (CD8) T cells and Langerhans cells (CD1+DR+) from the hair follicles during cyclosporine therapy. A significant decrease in the CD4/CD8 ratio occurred early in the course of treatment and was maintained throughout the therapy. This decrease suggests that cyclosporine not only cleared immune cells from the hair follicles but also altered the balance of regulatory lymphocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Intralesional cyclosporine in the treatment of psoriasis. A clinical, immunologic, and pharmacokinetic study

In a double-blind, vehicle-controlled study, all of six psoriatic plaques treated with intralesional cyclosporine administered three times weekly for 4 weeks showed complete clearing or incomplete but significant clearing in comparison with vehicle-treated plaques (p less than 0.01). Epidermal thickness decreased from 0.42 +/- 0.07 to 0.27 +/- 0.08 mm at 4 weeks (p less than 0.03). Biopsy specimens obtained on day 5, before any clinical improvement, revealed a significant reduction of epidermal DR+CD1- antigen-presenting cells, epidermal and dermal monocytes, and keratinocyte intercellular adhesion molecule-1 expression. By day 5 the stratum corneum reverted to normal in the plaques receiving cyclosporine. Pain at the injection site was the major side effect. Steady-state blood cyclosporine levels ranged from 20 to 30 ng/ml during the first 12 hours after injection and became undetectable at 48 hours. These data suggest that cyclosporine improves the skin of patients with psoriasis by a local mechanism of action.

Treatment of severe lichen planus with cyclosporine

Two patients with severe chronic lichen planus were successfully treated with oral cyclosporine (6 mg/kg/day). A response was noted within 4 weeks, and complete clearing was achieved after 8 weeks of treatment. No significant adverse effect was noted. The patients have remained in remission 3 and 10 months after therapy, respectively. Clinical improvement was accompanied by significant reduction in the T cell infiltrate in the skin. Abnormal expression of keratinocyte intercellular adhesion molecule-1 (ICAM-1), which was present before therapy, became undetectable after 1 week of cyclosporine therapy, before any significant clinical and histologic change.

Effects of ultraviolet radiation on the immune system in humans

In experimental animals, exposure to UV-B radiation produces selective alterations of immune function which are mainly in the form of suppression of normal immune responses. This immune suppression is important in the development of nonmelanoma skin cancer, may influence the development and course of infectious disease and possibly protects against autoimmune reactions. The evidence that this form of immune suppression occurs in humans is less compelling and very incomplete. The wavelengths of radiation most affected by a depletion of the stratospheric ozone layer are those known to be most immunosuppressive in animals and it is likely that such depletion will increase any suppressive effect of sunlight on immunity in humans. In addition to establishing whether or not UV-B radiation can cause suppression of immune function in humans, studies are required to determine if melanin can provide protection against such suppression, the role of this suppression in the pathogenesis of skin cancer, the development of infectious disease and vaccine effectiveness, and the capacity for humans to develop adaptive, protective mechanisms which may limit damage from continued exposure to UV-B radiation.

Characterization of factor XIIIa positive dermal dendritic cells in normal and inflamed skin

The immunocytochemical identification and characterization of indigenous dermal dendritic cells (dermal dendrocytes) using a rabbit polyclonal antibody to clotting enzyme factor XIII subunit A (FXIIIa) was carried out on normal and inflamed human cutaneous tissue. The immunophenotype of FXIIIa positive dendritic cells was analysed with a panel of 18 monoclonal antibodies using immunoperoxidase and double immunofluorescence staining techniques. The antibody against FXIIIa detected highly dendritic dermal cells located particularly in the upper reticular and papillary dermis. Double fluorescence microscopy showed that FXIIIa positive cells were bone marrow derived (HLe-I+) and co-expressed monocyte, macrophage or antigen presenting cell markers (HLA-DR+, LFA-I+, HLA-DQ+, OKM5+, Mo I+, Mono-I+, Leu M3+). No labelling was obtained with cell markers for Langerhans cells (CDI), T lymphocytes (CD2), granulocytes (LeuMI) fibroblasts (Te7), intercellular adhesion molecule-I (ICAM-I) or endothelial cells (Factor VIII related antigen). Gamma interferon induced increased expression of HLA-DR and co-expression of ICAM-I on FXIIIa+ dermal dendritic cells in normal skin in organ culture. Moreover, in benign inflammatory dermatoses such as atopic eczema and psoriasis there was an increased number of FXIIIa+, DR+, ICAM-I+ cells in the upper dermis and foci of FXIIIa+ cells in the epidermis closely associated with lymphocytes. FXIIIa positive cells in human skin represent a specific population of bone-marrow dermal dendritic cells, distinct from Langerhans cells, that share some features common to mononuclear phagocytes (monocyte/macrophages). In addition, the detection of HLA-DQ on 48% of FXIIIa+ cells and the lack of OKMI in combination with high OKM5 expression suggests an antigen-presenting cell phenotype.

Lymphocytes and macrophages of the epidermis and dermis in lesional psoriatic skin, but not epidermal Langerhans cells, are depleted by treatment with cyclosporin A

Since cyclosporin A (CsA) is an immunosuppressive agent, its beneficial effect in psoriasis suggests that immune cells may play a role in the pathogenesis and resolution of psoriasis. To determine early effects of CsA in psoriasis, we quantitated immune cells using double immunofluorescence microscopy on biopsy specimens obtained prior to therapy and after 3, 7, and 14 days of CsA therapy. CsA therapy resulted in significant reductions in the absolute number of immune cells (including T cells, monocytes/macrophages, and antigen presenting cells) contained within psoriatic skin. The effect was rapid, with over one-half of the reduction in the density of HLe1+ (human leukocyte antigen-1 positive or bone marrow derived) cells, including T cells, activated T cells, monocytes, and Langerhans cells (LCs), occurring within 3 days. Despite the overall reduction in the numbers of immunocytes in the skin, the proportion of T cells, Langerhans cells, and monocytes in relation to the total number of immune cells was unchanged with therapy, reflecting equally proportional losses of each subtype. Dermal CD1+DR+ cells (putative Langerhans cells), which are not found in normal skin but are present in lesional psoriasis skin, were virtually cleared from the papillary dermis after CsA therapy. Although absolute numbers of epidermal Langerhans cells, defined as cells expressing both CD1 (T6) and DR molecules (CD1+DR+), were also reduced after CsA, epidermal non-Langerhans CD1-DR+ cells (macrophages, activated T cells, DR- keratinocytes) demonstrated a proportionally greater decrease, with the ratio of CD1+DR+ Langerhans cells/non-Langerhans CD1-DR+ epidermal cells changing from a mean of 0.82 at baseline to 1.92 at day 14.(ABSTRACT TRUNCATED AT 250 WORDS)

Immediate decrease in antigen-presenting function and delayed enhancement of interleukin-1 production in human epidermal cells after in vivo UVB irradiation

Human skin was irradiated in vivo with a single UVB dose (100 mJ/cm2 or 200 mJ/cm2) to examine simultaneously the antigen-presenting function and interleukin-1 (IL-1) production capacity of irradiated epidermal cells (EC). Suction blisters were produced on irradiated areas on days 0, 3 and 7 after UVB. Irradiated EC were harvested and co-cultured with autologous T lymphocytes in the presence of antigens (PPD, HSV) or mitogen (ConA). Culture supernatants were tested for IL-1 activity using the thymocyte comitogenity assay. We found that a single 200 mJ/cm2 dose of UVB caused an immediate suppression of the antigen-presenting function of EC, but no alteration in their IL-1 production capacity or surface marker expression (ATPase, CDI). PPD- and HSV-induced lymphocyte proliferation was decreased 70-80% and ConA-driven proliferation 30% when compared to non-irradiated EC. However, this suppression was restored on days 3 and 7 after UVB irradiation, this being coexistent with an increased capacity of EC to produce IL-1. It remains to be elucidated whether the immediate UVB-induced photoimmunosuppression observed in the present study is due to inhibitory mediators or impaired membrane function of EC or both.

Distribution patterns of the OKM 5 antigen in normal and diseased human epidermis

The distribution of OKM 5-positive dendritic cells in the epidermis was investigated in 75 cases of inflammatory dermatoses and in 14 cases of normal human skin by immunohistochemical and morphometric methods. Furthermore 6 cases of normal human skin, 14 cases of nevocellular nevi, 26 cases of malignant melanoma, 7 cases of contact dermatitis and 6 cases of mycosis fungoides have been examined with special emphasis on the expression of OKM 5 antigen on keratinocytes. OKM 5-positive dendritic cells were present in normal human epidermis at a density of 46 +/- 3.4 cells/mm2 section area. However, there was a significant increase in cutaneous drug eruptions (166 +/- 17.2 cells/mm2; U-test: p less than or equal to 0.05). Concerning OKM 5-positive keratinocytes, a mean percentage of 10.2% +/- 5.0% OKM 5-positive keratinocytes was found in nevocellular nevi, compared to 0.5% +/- 0.5% in the adjacent skin. The corresponding values for malignant melanomas were 52.5% +/- 3.4% (lesional epidermis) and 7.1% +/- 2.2% (adjacent epidermis). There were significant differences of both lesional and adjacent epidermis between nevi and melanomas (U-test: p less than or equal to 0.05). Our cases of contact dermatitis revealed a mean percentage of 19.3% +/- 6.7% OKM 5-positive keratinocytes, whereas in mycosis fungoides the corresponding value represents 42.7% +/- 6.2%. The differences between the percentage of OKM 5-positive keratinocytes in normal epidermis and contact dermatitis as well as mycosis fungoides were significant (U-test).(ABSTRACT TRUNCATED AT 250 WORDS)