The effects of ultraviolet light and certain drugs on La-bearing Langerhans cells in murine epidermis

Epicutaneous Administration of 17β-Estradiol Induces Langerhans Cells Depletion

BACKGROUND

Langerhans cells (LC) number and function in mouse vaginal mucosa are affected by 17β-estradiol (E₂) application; nonetheless, its effect on epidermal LC has not been studied. The purpose of this study was to evaluate the effect of topical administration of E₂ on the number, phenotype, and migratory ability of LC in mouse skin.

METHODS

Ears of adult CD1 male mice were topically treated once with several doses. Immunohistochemical staining for CD207 and TUNEL staining were performed. LC migration to lymph nodes and the effect on the expression of costimulatory molecules on cultured dendritic cells (DC) were also evaluated.

RESULTS

E₂ decreased the number of CD207+ LC in a dose-dependent manner. One hour after treatment, 1 and 10 µg/mL E₂ significantly reduced the LC number by 21% and 26%, respectively, after two hours, the reduction was 23% and 41%, respectively. After 48 hours, LC recovered, and after 96 hours of treatment, the CD207+/MHCII+ DC numbers were increased in regional lymph nodes. However, CD86 and CD40 molecules were expressed at lower levels than in positive control. The TUNEL assay did not show apoptotic cells. Furthermore, in cultured DC, E₂ promoted a decrease in CD40 and CD86 expression and an increase in CD273, CD274, MHCII, and CCR7.

CONCLUSIONS

The topical administration of E₂ induced a transitory local diminution of LC population and a tolerogenic phenotype. This decrease in epidermal LC suggests that E₂ may affect skin immune responses, inducing an inhibitory response, which should be considered when prescribing topical E₂ medications.

Duration of topical therapy in the maintenance of atopic dermatitis remission in pediatric age

BACKGROUND

Topical corticosteroids (TCS) are the first-choice treatment for atopic dermatitis (AD) flares. In literature there are clear advice about the potency, dosage and frequency of application of TCS, but there are no shared indications about duration of the treatment during a flare. The aim of the study is to demonstrate if the use of a steroid cream for less than or 5 days, could be equal or more effective than the application for more than 5 days during a flare episode, in keeping a remission state of AD.

METHODS

The study population (N.=122) was selected according to the following inclusion criteria: at least one specialist allergological and dermatological examination in the period November 2015 to February 2017, age between 1 and 11 years; mild to moderate atopic dermatitis. All patients were given a standardized telephone questionnaire, which concerns on multiple aspects: parents' self-reported perceptions of the severity of their child's condition; actual use of emollients, moisturizers and steroid creams; number of consecutive days of using of topical steroid cream during an exacerbation of AD; average number of AD exacerbations per month in the last year; total number of AD exacerbations in the last year.

RESULTS

Data from 96 patients was examined. We classified three groups of patients from data collected: group 1 (N.=40): use of TCS for ≤5 consecutive days during an exacerbation event of AD; group 2 (N.=12): use of TCS for >5 consecutive days during an exacerbation event of AD; group 3 (N.=44): nonuse of TCS or use of TCS with a different posology. We found a further subgroup in group 3 (3a, N.=27) with patients using only emollient crème in AD management. In group 1, 27 patients (67.5%) did not show a good AD control; on the contrary, 13 patients (27.5%) reported a good AD control. In group 2, 4 patients (25%) did not show a good AD control; on the contrary, 8 patients (75%) reported a good AD control. By comparing the data obtained in the presence of good AD control, the difference between the percentages obtained was found to be statistically significant (P=0.034).

CONCLUSIONS

The results obtained show that a therapeutic pattern based on the use of TCS for a duration of more than 5 consecutive days during an episode of AD exacerbation is more efficient than the proposed alternative therapeutic scheme in the maintenance of AD remission.

Rationale Behandlung von Patienten mit Verbrennungen 1. Grades

First-degree burns are the most common type of burn, but are often inadequately treated. The methods of treatment and the course of healing are poorly documented owing to the fact that first-degree burns are generally not considered to be a serious injury. First-degree burns can be caused by thermal injury or UV irradiation (sunburn). The pathophysiology and the therapeutic approach are similar, although the damage follows a different time course for each injury--immediate damage after contact with hot objects, liquids or fire, delayed damage after sun exposure. After initial cooling with water, aqueous emulsions with small amounts of well-tolerated lipids (O/W emulsions) are best suited for treating first-degree burns or sunburn. Water evaporates producing cooling and reducing inflammation; the lipids accelerate the repair of the damaged skin barrier and reduce drying. Foam sprays and lotions are ideal because they are easy and painless to apply. The use of topical corticosteroids is not recommended, as superiority to the vehicle has not been shown.

Corticosteroids But Not Pimecrolimus Affect Viability, Maturation and Immune Function of Murine Epidermal Langerhans Cells

Given the importance of dendritic cells in the immune response, we investigated the effect of corticosteroids (CS) on the integrity, survival, and function of murine Langerhans cells (LC) in comparison with pimecrolimus, a novel anti-inflammatory drug for the topical treatment of atopic dermatitis. BALB/c mice were treated twice on one day with ethanolic solutions of the compounds. At 24-72 h after the last application, we observed fragmented DNA, caspase-3 activity, and an upregulation of CD95 expression in LC from mice treated with CS but not in LC of pimecrolimus- or vehicle-treated animals. CS-epidermal cell (EC) supernatants but not pimecrolimus-EC supernatants contained significantly lower amounts of soluble factors (GM-CSF, TNF-alpha, IL-1alpha) required for LC survival and maturation than EC supernatants from vehicle-treated mice. With regard to LC maturation, CS but not pimecrolimus inhibited the expression of CD25, CD205, and costimulatory molecules. In line with this, LC from pimecrolimus-treated mice were similar to LC from vehicle-treated mice in their capacity to stimulate antigen-presenting function and migration, whereas LC from CS-treated mice were greatly impaired in these abilities. In summary, our data show for the first time that CS but not pimecrolimus induce apoptosis in LC in situ, implying that the prolonged use of CS could have adverse effects on the skin immune system.

Skin changes in "screen dermatitis" versus classical UV- and ionizing irradiation-related damage--similarities and differences

An increasing number of persons say that they get cutaneous problems as well as symptoms from certain internal organs, such as the central nervous system (CNS) and the heart, when being close to electric equipment. A major group of these patients are the users of video display terminals (VDTs), who claim to have subjective and objective skin- and mucosa-related symptoms, such as pain, itch, heat sensation, erythema, papules, and pustules. The CNS symptoms are, e.g. dizziness, tiredness, and headache. Erythema, itch, heat sensation, edema and pain are also common symptoms of sunburn (UV dermatitis). Alterations have been observed in cell populations of the skin of patients suffering from so-called "screen dermatitis" similar to those observed in the skin damaged due to ultraviolet (UV) light or ionizing radiation. In "screen dermatitis" patients a much higher number of mast cells have been observed. It is known that UVB irradiation induces mast cell degranulation and release of TNF-alpha. The high number of mast cells present in the "screen dermatitis" patients and the possible release of specific substances, such as histamine, may explain their clinical symptoms of itch, pain, edema and erythema. The most remarkable change among cutaneous cells, after exposure with the above-mentioned irradiation sources, is the disappearance of the Langerhans' cells. This change has also been observed in "screen dermatitis" patients, again pointing to a common cellular and molecular basis. The results of this literature study demonstrate that highly similar changes exist in the skin of "screen dermatitis" patients, as regards the clinical manifestations as well as alterations in the cell populations, and in skin damaged by UV light or ionizing radiation.

Modulation of MHC class II+ Langerhans cell numbers in corticosteroid treated epidermis by GM-CSF in combination with TNF-alpha

It is important to understand how dendritic cells (DC) are recruited, maintained and stimulated to migrate from tissues to lymph nodes. This is because DC are potent initiators of primary immune responses and candidates for vaccine development. Identification of factors which could lead to increased numbers of DC in tissues could affect immune responses by modulating their interaction with antigen which penetrates the tissue. To identify cytokines which could increase DC in tissues we tested the ability of GM-CSF, TNF-alpha and IL-6 to partially prevent steroid depletion of Langerhans cells (LC) from the epidermis. Cytokines diluted in serum-containing medium were compared with cytokines diluted in albumin-containing, serum-free medium in order to determine a minimum combination of cytokines required to increase LC and the effect of serum on the LC-increasing activity of cytokines. In the presence of serum, GM-CSF or TNF-alpha could increase LC frequency compared to the control; but in the absence of serum neither of these cytokines were effective unless they were combined with each other. In the presence of serum the combination of GM-CSF with TNF-alpha was ineffective. The data support the hypotheses that GM-CSF and TNF-alpha are both important in regulating LC numbers in the epidermis in vivo. Serum may modulate how each of these cytokines, separately or in combination, affect LC frequency in the epidermis - GM-CSF and TNF-alpha separately probably interact with other factors present in serum to increase LC frequency, whereas in combination it is possible that these separate effects are cancelled in the presence of serum. TNF-alpha and GM-CSF together, in the absence of serum, form one combination of a minimum number of cytokines which can regulate LC frequency in the epidermis; and IL-6 alone, or in combination with GM-CSF, does not increase LC frequency.

Cell-mediated immunosuppressive mechanisms induced by UV radiation

Soon after UV exposure, mast cells degranulate, possibly because of the release of the mediators and cytokines from the epidermis, and there are subsequent vascular changes and cellular infiltration. Within a few hours, the soluble mediator milieu of UV-exposed skin becomes exceedingly complex and replete with interactions. Leukocytes newly entering the skin, as well as those already in the skin, must respond to these inflammatory signals. Altered antigen presentation and immune suppression likely derive from alterations induced in the APC that comprise the post-UV leukocyte population of the skin. Many of these mechanisms may explain the effectiveness of phototherapy in atopic dermatitis and psoriasis.

Modulation of Ia+ Langerhans cell numbers in vivo by cultured epidermis derived supernatants and by GM-CSF

This paper demonstrates that epidermal cells in culture produce an activity which can increase the frequency of Ia+ epidermal Langerhans cells (LC). This was achieved by treating mice topically with a mixture containing supernatant derived from primary culture of murine epidermis (ES) and a synthetic corticosteroid, triamcinolone acetonide (TAC). The presence of the supernatant in the mixture partially protected the Ia+ LC from depletion by the steroid. The Ia+ LC frequency increasing activity was measured as the difference between the Ia+ LC frequency due to treatment with steroid mixed with supernatant and the Ia+ LC frequency due to treatment with steroid mixed with negative control medium. The mean frequency of Ia+ LC in epidermis treated with TAC mixed with ES was 606(SD 43) cells/mm2, as compared with 486 (SD 68) cells/mm2 in the epidermis treated with TAC mixed with control medium. The activity appeared to be caused by (a) proteinaceous factor(s). A fraction of ES which was retained above a > or = 10 KDa molecular weight cut-off membrane was capable of partially protecting Ia+ LC frequency from TAC depletion. Supernatants from cultured lymph nodes, dermis as well as the squamous cell carcinoma lines T7 and T79, but not the human osteosarcoma cell-line 143B, also contained similar activities. We demonstrate that GM-CSF also increased the number of Ia+ epidermal LC when applied topically to mouse skin in this system. Therefore, using this Ia+ LC frequency modulation system, we propose that GM-CSF is one example of a cytokine which may be involved in the regulation of Ia+ LC numbers in epidermis and that epidermal cells produce factors which can increase the number of Ia+ LC.

Histochemical, immunohistochemical and ultrastructural studies on the action of glucocorticoids on epidermal Langerhans cells (ELC) of murine skin

We studied the influence of the glucocorticosteroids dexamethasone and prednisolone on epidermal Langerhans cells (ELC) in the ear skin of BALB/c mice. ELC were detected by HLA II-antigen-expression and ATPase staining. The number of ELC was counted by normal light and immunofluorescence microscopy. Both, dexamethasone and prednisolone decreased the number of ELC and the intensity of the reaction for HLA II and ATPase significantly. In the electron microscope, ELC were identified by their light cytoplasm, the lobulated nucleus and typical Birbeck Granula (BG). After systemic application of dexamethasone or prednisolone the ultrastructure was changed with respect to a loss of typical BG and occurrence of numerous small vacuoles without electron dense content instead of BG.

Ultraviolet B-induced local immunosuppression of contact hypersensitivity is modulated by ultraviolet irradiation and hapten application

The induction of contact hypersensitivity is suppressed when hapten is applied topically to an area irradiated by ultraviolet B (UVB). There is no standardized procedure to induce this local immunosuppression by UVB. We investigated the effects of the following factors on induction of dinitrofluorobenzene contact hypersensitivity in mice. UVB dose, divided UVB exposure, timing of sensitization after irradiation, hapten concentration, hapten volume (application area), sex, age, and simultaneous sensitization on UV-exposed and nonexposed skin. The suppression was enhanced by increasing the UVB dose. When 100 mJ/cm2 of UVB was irradiated, divided daily exposure (25 mJ x 4 d) was more suppressive than single exposure (100 mJ x 1 d). Sensitization 2 d after irradiation (100 mJ/cm2) induced suppression most effectively. When 25 microliters of dinitrofluorobenzene solution was applied to exposed skin, higher concentrations induced lower suppression. When the total dose of hapten was kept constant (92 micrograms), the application of lower concentrations to large areas (0.25%, 25 microliters) caused stronger suppression than higher concentrations (1%, 6.25 microliters) to small areas. Simultaneous sensitization on UV-exposed and nonexposed skin revealed less suppression than sensitization only on exposed skin. The suppression of contact hypersensitivity was significantly greater in young than in old mice. These results provide details that may be useful in designing studies involving immunosuppression by UVB radiation.

Long-term ultraviolet B-induced impairment of Langerhans cell function: an immunoelectron microscopic study

The influence of low-dose, long-term ultraviolet B (UVB) light exposure on HLA class II-positive human epidermal Langerhans cells (LC) was studied using a sensitive immunoelectron microscopic technique for the ultrastructural assessment of HLA class II expression on LC and for quantification of these cells in situ. Six healthy Caucasian volunteers participated in the experiments and received thrice weekly UVB treatments for 4 weeks. The initial dose ranged from 30 to 50 mJ/cm2 and the total dose from 600 to 3500 mJ/cm2, depending on skin type. Suction blisters and biopsies were obtained before the start of the UVB protocol and 48 h after the last UVB irradiation, and processed for the mixed epidermal cell-lymphocyte reaction (MECLR) and electronmicroscopy, respectively. The MECLR was used as a measure of the immune response. The distribution of HLA class II molecules on LC was studied by incubating ultrathin cryosections of human skin tissue with an anti-HLA class II MoAb that was conjugated to 10 nm colloidal gold. Furthermore, the number of LC was assessed ultrastructurally, when they could be recognized by their unique cytoplasmic organelle, the Birbeck granule (BG). The UVB protocol that was employed caused a marked suppression of the MECLR responses. This UVB-induced reduction of the immune response was not paralleled by changes in HLA class II expression on LC, nor in the number of epidermal LC. These findings are further support for our hypothesis that UVB-induced immune suppression in the skin is not due to a depletion of local LC.

Major histocompatibility class II antigen expression on the surface of epidermal cells from normal and ultraviolet B irradiated subjects

The influence of ultraviolet B irradiation in therapeutic doses on MHC II-positive epidermal cell numbers and their surface MHC II antigen expression was studied quantitatively using light microscopic immunoperoxidase and immunogold electron microscopic techniques. In multiple ultrathin sections through many MHC II-positive epidermal cells from five healthy subjects, prior to ultraviolet exposure, Langerhans cells and indeterminate cells were found to express similar densities of surface MHC II antigens, which were uniformly distributed over the cell surface. The variation in surface MHC II antigen expression on 97 dendritic epidermal cells from one subject was normally distributed. Following a 6-week course of ultraviolet B irradiation, in the same doses as those normally used for the treatment of psoriasis, MHC II-positive epidermal cell numbers were significantly reduced (mean decrease to 51% of the pre-UVB sample; p < 0.001 analysis of variance), but their surface MHC class II antigen density was significantly increased (p < 0.05 analysis of variance). No MHC II-negative Langerhans cells were detected in either the pre- or post-UVB samples.

Mechanisms of local, low-dose UVB-induced immunosuppression in contact hypersensitivity

Preirradiation of contact sensitizing sites to low-dose ultraviolet B (UVB) renders animals unresponsive to challenge reaction. This unresponsiveness is known as local, low-dose UVB-induced immunosuppression. Although researchers in this area have developed theories, the exact mechanisms of UVB-induced immunosuppression are still a matter of controversy. This article reviewed various scientific data on UVB-induced immunosuppression, categorizing them into individual sequential steps in the whole cascade.

PUVA augments cyclosporine A-mediated rat cardiac allograft survival

PUVA, the administration of the photosensitizer 8-methoxypsoralen (8-MOP) followed by exposure of the skin to longwave ultraviolet radiation (UVA, 320-400 nm), is employed clinically for the treatment of skin diseases. PUVA is immunosuppressive and we have shown previously that it can significantly prolong skin allograft survival. This enhanced survival is associated with reduced spleen cell cytotoxic activity against donor cell targets with preserved ability of treated animals to be immunized to third-party alloantigens 5 days after exposure to a course of PUVA. To examine whether PUVA may potentiate the effect of cyclosporine A (CYA) in inhibiting cardiac allograft rejection, we employed a rat cardiac transplant model. Lewis rats (RT1(1) received cardiac allografts at a heterotopic site from Lewis Brown Norwegian (RT1(1/n)) hybrid donors. Seventy animals were equally divided into 10 groups. Starting on the day of surgery, three groups received a suboptimal doses of CYA (1.5, 4.5, or 9.0 mg/kg im), three groups received the same doses of CYA and 1.0 mg/kg of 8-MOP injected ip followed by 6.35 J/cm2 of UVA radiation to their shaved dorsums (PUVA), one group received PUVA alone, one group received UVA radiation alone, one group received 8-MOP alone, and the final group received no treatment. Therapy was carried out daily for 7 days and survival of the allograft was assessed by daily palpation of the transplanted heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Side-effects of psoralen photochemotherapy (PUVA)

Although psoralen photochemotherapy (PUVA) is one of the most effective forms of therapy for psoriasis, the risk of potential long-term side-effects is, as yet, not clearly determined. Chronic degenerative and pigmentary skin changes similar to those of chronic solar exposure occur after long-term PUVA treatment; PUVA also causes non-melanoma skin cancers in man, although there is, as yet, no consensus as to what cumulative phototoxic PUVA dose is carcinogenic. Long-term multicentre studies from the U.S.A. indicate a definite risk of squamous cell carcinoma for long-term PUVA-treated patients, whereas European studies reveal no overall increase in skin cancers in similar patients except for those exposed to other carcinogens. Assignment to PUVA should be based on the risk:benefit ratio for the individual patient. Careful patient selection is therefore mandatory and should be limited to those who can be monitored and controlled by informed, competent and conscientious physicians.

UVB radiation and DNFB skin painting induce suppressor cells universally in mice

Ultraviolet radiation (UVR)3 from within the spectrum B (UVB) has the capacity to distort the induction of contact hypersensitivity (CH) in murine skin. A damaging effect of UVB on epidermal Langerhans cells (LC) appears to be universal in all genetically defined strains of mice tested. However, while UVB impairs the induction of CH in some strains of mice, it has no apparent effect on CH in others. Thus, a disparity exists between the effects of UVB on LC and on CH. This is a paradox because LC are generally regarded to serve as the antigen-presenting cells of the skin, placing them at the earliest stages of induction of CH. One possible explanation for this paradox has been that UVB-susceptible strains of mice may generate hapten-specific suppressor T cells, whereas their UVB-resistant counterparts may not, when their skin is treated with UVR and painted with haptens such as dinitrofluorobenzene (DNFB). This possibility was excluded by examining the capacity of UVR and hapten to generate suppressor T cells in several different inbred strains of mice. The results indicate that the induction of hapten-specific afferent T suppressor cells is a universal sequela to treatment of mice with UVB and hapten, irrespective of whether the mice display the phenotype of vigorous CH or not. Thus, the genetic basis of UVB-resistance does not reside in the ability of UVR to induce suppressor T cells. Rather, attention should now be focused on its ability to interrupt induction of effector mechanisms.

A study of systemic and topical effects of topical steroid application through the comparison of two application schedules

We compared two application schedules of a topical steroid, BV (Betamethasone valerate). The schedules were once daily and twice a week on juvenile Wistar rats treated for four weeks. Steroid actions were assessed topically (skin thickness and epidermal Langerhans cell density) and systemically (body weight and internal organ wet weights). The results revealed some rather severe systemic effects caused by frequent steroid application. And we also found a uniquely weak BV effect with Langerhans cells compared to obvious systemic effects on rats. We came to the conclusion that frequent steroid application to the young should be avoided.

Identification of the molecular target for the suppression of contact hypersensitivity by ultraviolet radiation

This study was conducted to explore the involvement of DNA damage in the suppression of contact hypersensitivity (CHS) by UV irradiation. The opossum, Monodelphis domestica, was used because cells of these marsupials have an enzyme that is activated by visible light (photoreactivating enzyme) and repairs ultraviolet radiation (UVR)-induced pyrimidine dimers in DNA. A single dose of 1,500 J/m2 of UVB (280-320 nm) radiation, representing 2 minimal erythema doses, was administered to the dorsal skin of opossums. This treatment prevented the opossums from developing a CHS response to dinitrofluorobenze (DNFB) applied either at the site of irradiation or an unirradiated site. In addition, this dose of UVR decreased the number of ATPase+ epidermal Langerhans cells in the dorsal epidermis to approximately 3% of that in unirradiated skin at the time of DNFB application. Treatment of the animals with wavelengths that activate the repair enzyme (320-500 nm, photoreactivating light, PRL) for 120 min immediately after UV irradiation inhibited the UVR-induced suppression of CHS almost completely. Exposure to PRL before UVR did not prevent UVR-induced suppression of CHS. PRL treatment after UV irradiation also prevented the decrease in the number of ATPase+ Langerhans cells. Measurements of lesions in DNA indicated that PRL treatment removed around 85% of the UVR-induced pyrimidine dimers. These data provide direct evidence that DNA, and most likely, the pyrimidine dimer, is the primary molecular target for the UVB-induced suppression of contact hypersensitivity to haptens applied to irradiated or unexposed skin.

Effect of psoralens and ultraviolet radiation on murine dendritic epidermal cells

Monofunctional psoralens produce less phototoxicity than bifunctional psoralens after ultraviolet A (UVA) irradiation. We investigated the effect of repetitive treatments with angelicin (isopsoralen), a monofunctional psoralen, plus UVA radiation (IPUVA) on the number and morphology of dendritic epidermal cells (dEC). This effect was compared with that of 8-methoxypsoralen plus UVA radiation (PUVA), UVA alone, and UVB radiation. C3H/HeN mice were treated topically with the drugs three times/wk for 4 consecutive wk; followed each time by 1 or 2.5 J/cm2 of UVA radiation. Other groups of mice were treated with the drugs alone, UVA alone, or 0.81 J/cm2 of UVB. Epidermal sheets were stained for ATPase, Ia, and Thy-1 markers. Mice treated with PUVA and UVB exhibited severe phototoxicity, whereas no overt phototoxicity was observed in mice treated with IPUVA, UVA alone, or the drugs alone. Early during the PUVA and UVA treatments the ATPase marker was lost from dEC, followed by loss of the Ia marker; the Ia marker was lost before the ATPase marker from dEC in animals treated with IPUVA. At the end of the treatment, however, nearly total depletion of ATPase+, Ia+, and Thy-1+ dEC was observed in mice treated with PUVA and IPUVA. UVB radiation caused rapid depletion of Thy-1+ dEC as well as ATPase+ and Ia+ cells. During treatments with IPUVA, PUVA, UVA, and UVB, the Langerhans cells became rounded and lost their dendrites. These changes were quantitated by image analysis. We conclude that alterations of cutaneous immune cells can occur in the absence of overt phototoxicity, and that monofunctional and bifunctional psoralens plus low dose of UVA radiation may have different effects on dEC markers.

Direct effects of glucocorticosteroids on epidermal Langerhans cells

To determine the direct effects of glucocorticosteroids on epidermal Langerhans cells (LC), we treated isolated LC with dexamethasone (DEX) in vitro, and investigated Ia expression by LC using immunofluorescence microscopy and FACS analysis. We found that DEX directly decreased the number of Ia+ LC in a dose- and time-dependent manner. Pulse incubation with DEX also inhibited the immunostimulatory function of LC in vitro. FACS analysis demonstrated that LC detected in DEX-treated culture expressed a similar amount of Ia antigen and Fc receptor on the cell surface as LC cultured with the solvent control, suggesting that LC may be composed of a heterogeneous population in terms of sensitivity to DEX, and DEX may completely abolish the expression of surface molecules on a subpopulation of LC or may be cytolytic to this sensitive population.

Disparate effects of in vitro low-dose UVB irradiation on intravenous immunization with purified epidermal cell subpopulations for the induction of contact hypersensitivity

Low-dose ultraviolet (UV) B irradiation suppresses contact hypersensitivity (CH) reactions and alters the antigen-presenting function of epidermal cells (EC) in mice. To identify the EC sources of immunosuppression in this system, we examined the effect of UVB on the capacity of EC to induce and to regulate CH to trinitrochlorobenzene (TNCB). On day 0, cell sorter-purified populations of Ia+EC, Thy-1+EC, or Ia-/Thy-1-EC from CBA and C3H/HeJ mice were exposed to 200 J/m2 UVB from unfiltered FS20 Sunlamps, derivatized with hapten, and inoculated intravenously into syngeneic mice (5000 cells per inoculum). After 6 d, responsiveness was tested by challenging the left ear with 2% TNCB and measuring ear swelling responses. On day 14, regulation was tested by painting 7% TNCB on abdominal skin; after 6 d the right ear was challenged. Whereas mice which received haptenated unirradiated Ia+EC exhibited full CH responses without down-regulation, mice inoculated with haptenated irradiated Ia+EC displayed significantly diminished primary responses and, on subsequent immunization, displayed down-regulation. On the other hand, panels of mice that received haptenated unirradiated Thy-1+EC, and haptenated irradiated Thy-1+EC both showed hyporesponsiveness as well as down-regulation. Intravenous immunization with haptenated unirradiated Ia-/Thy-1-EC or with haptenated irradiated Ia-/Thy-1-EC led in each instance to immunologically "null events." These findings indicate that UVB irradiation profoundly affected Ia+EC such that their capacity to sensitize for CH was not only abrogated, but that such treatment also resulted in down-regulation of CH responses. By contrast, the same phototreatment had no effect on the inherent property of Thy-1+EC to mediate down-regulation of CH. We conclude that Ia+EC are immunologically relevant targets of low-dose UVB radiation, and that two populations of irradiated EC, Ia+EC, and Thy-1+EC, have the potential to deliver down-regulatory signals in this model of immunosuppression.

Flow cytometrically-sorted residual HLA-DR+T6+ Langerhans cells in topical steroid-treated human skin express normal amounts of HLA-DR and CD1a/T6 antigens and exhibit normal alloantigen-presenting capacity

Topical corticosteroids decrease the number of HLA-DR+T6+ Langerhans cells (LCs) and the antigen-presenting capacity of epidermal cells (ECs). We have investigated the properties of residual HLA-DR+T6+ LCs in steroid-treated human skin. Flow cytometric analysis revealed that clobetasol propionate 0.05% applied twice daily for 7 d reduced the percentage of HLA-DR+T6+ LCs in EC suspensions to 46% of control (from a mean percentage +/- sem of 2.49 +/- 0.30 in control skin to 1.15 +/- 0.22 in steroid-treated skin), but did not significantly alter the relative amounts of HLA-DR and CD1a/T6 antigens per individual HLA-DR+T6+ cell. HLA-DR+T6- and HLA-DR-T6+ cells were not detected in either group. Steroid therapy significantly decreased the allostimulatory capacity of unsorted ECs. By contrast, in parallel experiments in which the same EC suspensions were greatly enriched (85% to 90%) for HLA-DR+T6+ LCs by flow cytometric sorting, the allostimulatory capacity of purified LCs from steroid-treated skin was not significantly different from control. Residual HLA-DR+T6+ LCs, which preserve their antigenic markers and alloantigen-presenting function, may be relatively unaffected because they have only recently immigrated into the epidermis, or they may represent a subgroup of steroid-resistant LCs. Alternatively, given the dose response relationship between topical steroid potency and decrease in HLA-DR+T6+ LC numbers, the apparent steroid resistance of residual HLA-DR+T6+ LCs may reflect heterogenity in the density of expression of LC steroid receptors.

Class II antigen expression of epidermal Langerhans cells in renal allograft recipients

This study was designed to investigate the influence of systemic immunosuppressive therapy on the HLA-DR expression of epidermal Langerhans cells. Fifteen renal allograft recipients immunosuppressed with cyclosporin A and steroids were studied. Skin biopsies were taken from the upper arm prior to transplantation and at different intervals during the post-transplantation period. The epidermis was separated from the dermis, and the epidermal sheet was subjected to immunohistochemistry in order to make the HLA-DR antigens on the Langerhans cells visible. Following 2 days of immunosuppression, the number of Langerhans cells expressing HLA-DR antigens started to decrease and after 1 week, only 60% of the initial number of positive cells were detected. The number of positive cells remained low throughout the experimental period. It is suggested that systemic immunosuppressive therapy will suppress the expression of HLA-DR antigens on epidermal Langerhans cells, something which may mirror a systemic effect on other antigen-presenting cells.

Relative lack of systemic effects of mometasone furoate on Langerhans cells of mice after topical administration as compared with other glucocorticosteroids

The effects of topically applied mometasone furoate were compared with those of other glucocorticosteroids, in particular fluocinolone acetonide, in assays of murine epidermal Ia+ Langerhans cell density. No evidence of systemic effects, as determined by a decline in the density of Ia+ LC in distant sites, was detected after local topical applications (5 times a week) of mometasone furoate 0.001% for periods of up to 3 weeks. Other steroids, even in such very low concentrations, and mometasone furoate in higher concentrations, produced systemic effects on Ia+ LC when used for longer than 5 d. The recovery time of Ia+ Langerhans cells is significantly shorter after application of mometasone furoate than after fluocinolone acetonide. However, with both compounds, recovery occurred more rapidly after 3 weeks than after a 1- or 2-week interval of compound administration.

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)

Effects of low or high doses of short wavelength ultraviolet light (UVB) on Langerhans cells and skin allograft survival

Since Langerhans cells (LC) are normally the only cells within the epidermis to express the class II major histocompatibility complex (MHC) transplantation antigens, depletion of LC could be expected to prolong skin allograft survival by reducing the antigenic disparity between host and recipient. To assess this hypothesis, donor C57BL mouse shaved dorsal trunk or tail skin was exposed to high (200 mJ/cm2) or low (40 mJ/cm2) doses of short wavelength ultraviolet light (UVB) before grafting on to the thorax of BALB/c mouse recipients of the same sex. These strains have different major and minor transplantation antigens. The effects of UVB treatments on LC were determined by electronmicroscopy. Skin grafted 1-14 days following a single high dose of UVB irradiation was ultrastructurally depleted of LC and survived significantly longer than unirradiated skin before being rejected. After a 21-day interval between exposure and grafting when LC were again present in the epidermis there was no significant difference between treated and control graft survival. Exposure to low dose UVB irradiation only significantly increased graft survival for skin transplanted 1-3 days after irradiation; skin grafted 4 days following irradiation survived for a similar period to unirradiated control skin grafts. Electronmicroscopy showed that the low UVB dose did not deplete LC from the epidermis. We conclude that after low dose UVB treatment the class II MHC antigens on the LC plasma membrane were lost temporarily, thus prolonging graft survival, but when the plasma membrane antigens were re-expressed graft survival returned to normal.(ABSTRACT TRUNCATED AT 250 WORDS)

T6+ and HLA-DR+ cell numbers in epidermis of immunosuppressed renal transplant recipients

The increased susceptibility of the skin of chronically immunosuppressed individuals to viral infections and sunlight-induced malignancies suggests specific drug-induced, dysfunction of local immune mechanisms within the sun-exposed skin of these individuals. To help understand the effect of immunosuppressive therapy alone in the absence of ultraviolet light on the immune system of skin, biopsies were collected from non-sun-exposed buttock skin of control, healthy volunteers and kidney transplant recipients immunosuppressed with either azathioprine/prednisone or cyclosporin A/prednisone and examined for incidences of T6+, and HLA-DR+ cells. No significant differences in the incidences of these 2 cell types were found (a) between control individuals and transplants recipients, (b) between transplant recipients receiving either of the immunosuppressive drug regimes, or (c) between transplant recipients who either had or had not developed skin cancer.

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.

Effect of UVB radiation on the biosynthesis of HLA-DR antigens

HLA-DR molecules on the surface of immunocompetent cells are thought to represent target structures for the immunomodulating effects of UV radiation during the induction of an immune response. We therefore investigated the effect of UVB radiation on the de novo synthesis of HLA-DR-gamma-chains in the cytoplasm and the expression of alpha- and beta-chains on the surface of the human lymphoblastoid B-cell line Raji. Raji cells were UVB irradiated before biochemical experiments were performed. Cells were then metabolically labeled or radioiodinated and detergent lysates immunoprecipitated using antibodies directed against the gamma- or the alpha- and beta-chain of the HLA-DR molecule. Over a wide dose range, UVB-irradiated Raji cells were shown to still express HLA-DR determinants on their surface and, even more importantly, to be capable of synthesizing HLA-DR-alpha, beta- and gamma-chains in a normal fashion. Despite this, the functional capacity of Raji cells was impaired in a dose-dependent manner. UV radiation thus seems to exert its immunomodulating effects primarily at a different level than the incriminated immune-response-associated antigens, which are expressed as recognition structures on the surface of immunocompetent cells.

Oxygen intermediates are involved in ultraviolet radiation-induced damage of Langerhans cells

Experiments were conducted to determine whether ultraviolet (UV) radiation exerts its effect through the generation of oxygen intermediates on Langerhans cells (LC). Guinea pigs were exposed to one single dose of UVB (0.9-2.7J/cm2), and biopsy specimens were taken 5 days after the irradiation. The population of LC was evaluated using ATPase-stained epidermal sheets. These exposures reduced the number of LC to 20-25% of the original density. On the other hand, superoxide dismutase (SOD) (0.02-0.2 mg), a scavenger of superoxide anion, which had been injected intradermally just before UV radiation, significantly prevented the depletion of LC, although not completely (37-40% of the original density). The injection immediately after the exposure was still significantly effective, but less so. Other scavengers of oxygen intermediates including catalase, D-mannitol, and L-histidine revealed no detectable effect. A single exposure of UVB at doses of 0.3-0.6 J/cm2 did not deplete the ATPase-positive LC. However, the same dose of UVB reduced the number of LC to 70%, when exposed after the injection of an SOD inactivator, diethyldithiocarbamate, possibly due to inactivation of physiologically existing SOD. These observations indicate that oxygen intermediates such as superoxide anion or its subsequent species are generated by UV radiation exposure and damage the epidermal LC.

Suppression of the cutaneous immune response following topical application of the prostaglandin PGE2

UVB irradiation (290-320 nm) and topical applications of arachidonic acid (AA) in mice decrease the number of identifiable Langerhans cells and alter the cutaneous immune response. Application of contact allergens such as dinitrofluorobenzene (DNFB) to irradiated or AA-treated skin induces antigen-specific tolerance. Indomethacin (IM), a cyclooxygenase inhibitor, administered orally to mice prior to UVB irradiation or prior to the topical application of arachidonic acid, abrogates suppression of contact hypersensitivity (CHS) to DNFB. This suggests a byproduct of arachidonic acid generated through the cyclooxygenase pathway may be involved in the immune suppression. Topical application of various prostaglandins (PGE2, PGD2, PGF2 alpha, and CTXA2) did not cause alterations in the population density of the identifiable Ia+ dendritic Langerhans cells. PGE2, but no other tested agent, produced a suppression of the CHS response to DNFB. These observations suggests that of the various prostaglandins, PGE2 might be one of several biochemical signals which mediate the suppression of contact hypersensitivity reactions following ultraviolet radiation exposure. However, the mechanisms by which PGE2 produces its suppressive effects have not been identified.

Prolongation of murine skin allograft survival by the systemic effects of 8-methoxypsoralen and long-wave ultraviolet radiation (PUVA)

Systemic administration of the photoactive drug 8-methoxypsoralen to a group of mice bearing cutaneous allografts, followed by exposure to long-wave ultraviolet radiation (UVA, 320-400 nm) (PUVA) daily for 14 days at a site distant from the allograft, significantly increased the survival time of the allografts. This effect was seen both in donor-recipient combinations that differ at the major histocompatibility complex and in those differing only at minor histocompatibility loci. Treatment with 8-methoxypsoralen or long-wave UV radiation alone was ineffective in prolonging allograft survival, as were doses of mid-wave UV radiation (UVB, 280-320 nm) that produced greater inflammation than the PUVA protocol. Allografted, PUVA-treated animals also demonstrated decreased alloantigen reactivity against donor-strain spleen cells during the period of treatment by cytotoxicity assays. Allografts of skin in the murine system are highly immunogenic and are generally rejected faster than organ allografts; thus PUVA treatment appears to exert a potent effect on prolonging allograft survival. The systemic nature of the effect and the fact that adverse side effects from PUVA are largely limited to the skin suggest that PUVA might have a role in clinical organ transplantation management.

Effect of orally administered aromatic retinoid on murine Langerhans cells

The effect of orally administered aromatic retinoid (Ro 10-9359) on murine epidermal Langerhans cells (LC) was studied in vivo and in vitro. Daily administration of retinoid caused a transient increase in LC density, as determined by staining for Ia antigens, during the first few days of treatment and thereafter a continuing decrease that reached a maximum at 2 weeks. In addition, the morphology and location in the epidermis had been altered. When the treatment was continued to 4 weeks, the density of LC returned to normal. The Ia-antigen-presenting function of epidermal cells to an allo-Ia-reactive cloned T cell line was elevated at all stages of retinoid treatment examined. This elevation did not correlate with the density of histochemically stainable Ia+ LC. These findings suggest that orally administered retinoid profoundly alters the functional capacity of Ia+ LC.

Further evidence for the self-reproducing capacity of Langerhans cells in human skin

The limited number of Langerhans cells (LC) in the epidermis is one of the main reasons for the technical difficulties in resolving the question of LC kinetics. In the present paper, we describe a method to evaluate the LC replication potential in epidermis. The procedure is based on the specific incorporation of bromodeoxyuridine (BrdU), a thymidine analogue, into the DNA during the S-phase of the cell cycle. Mice, bearing human skin grafts, were injected s.c. every 6 h for up to 17 days with BrdU. At different times, the incorporated BrdU as well as the human epidermal LC were revealed on skin sections using anti-BrdU and OKT-6 monoclonal antibodies, respectively. After 6 h, 4.9% of the LC were labeled with BrdU. Then, the number of OKT-6(+) BrdU(+) cells increased in a linear manner and achieved 34% at 120 h, 67% at 240 h, and 94% at 400 h during the course of continuous labeling procedures. Based on this result we calculated a total cell cycle time of 392 h (16.3 days) and 12 h for the S-phase for human epidermal LC. Applying this technique, we were able to show also that 48 h after local treatment with 12-O-tetradecanoylphorbol-13-acetate or after stripping, the number of BrdU-labeled LC was considerably increased. Furthermore, after i.p. injection of colchicine in the nude mouse, human epidermal LC undergoing mitosis were evidenced by electron microscopy in the graft. From these results we conclude that the LC are actively cycling--therewith a self-reproducing cell population in human epidermis.

In vitro suppression of the epidermal Langerhans' cells in necro split skin

The effect of ultraviolet light B irradiation and glucocorticosteroid incubation on the epidermal Langerhans' cell density and tissue viability was investigated, in vitro, on human thin necro split skin.

Differential analysis of experimental hypermelanosis induced by UVB, PUVA, and allergic contact dermatitis using a brownish guinea pig model

In moderately colored guinea-pig skin, UVB, PUVA, and allergic contact dermatitis were shown to induce hyperpigmentation that resembled the pigmentary changes observed in mongoloid human skin. Using this model, we examined the effects of chemical agents, including tyrosinase inhibitors and sunscreen agents, on the color changes induced by UV irradiation. The daily exposure of brownish guinea-pig skin to UVB irradiation at a variety of energies for 3 successive days induced clearly visible black pigmentation on the irradiated rectangular areas of the flank within a few days of irradiation, the maximum being reached about 1 week after irradiation, i.e., similar to the changes that occur in pigmented human skin. Split epidermal sheets prepared from untreated pigmented guinea pigs exhibited 200-400 melanocytes/mm2; 1 week after UV irradiation, the applied areas show an increased number of strongly dopa-positive melanocytes with stout dendrites (800-1,000 cells/mm2). UVA irradiation following an intraperitoneal injection of 8-methoxypsoralen (8-MOP) also produced black pigmentation 1 week after irradiation, and this was paralleled by a marked increase in the number of dopa-positive melanocytes in dopa-reacted split epidermal sheets. Allergic contact dermatitis produced by the application of 1-phenylazo-2-naphthol induced hyperpigmentation after an interval of about 14 days in 10 of the 21 allergy-acquiring animals examined. This induced pigmentation was accompanied by an increase in the number of dopa-positive melanocytes as compared to the number seen in controls. In contrast, allergic contact dermatitis produced by the application of dinitrochlorobenzene failed to induce such a high ratio of postpigmentation, with only 3 of the 21 allergy-acquiring animals showing hyperpigmentation and 5 showing depigmentation; in the latter, there was a slight decrease in the number of dopa-positive melanocytes. To study the preventive effect of tyrosine inhibitors on UVB-induced pigmentation, daily topical applications of these compounds were performed after three daily UVB irradiations. Treatment with 10% hydroquinone for 10 days interrupted UVB-induced pigmentation and resulted in a marked reduction in the number of epidermal melanocytes as compared to the number found in UVB-irradiated, untreated control skin.

The inhibitory effect of PUVA on the immunity of experimental dermatophytosis in guinea pigs

The effect of topical PUVA on the disease course and immunity of T. mentagrophytes dermatophytosis was investigated in guinea pigs. Animals which had been inoculated on nontreated skin showed mild erythematous lesions with scaling in a few days and then developed the most intense reaction between days 10 and 14. The lesions resolved completely by the third week. On the other hand, animals which had been inoculated on the PUVA-treated sites showed only mild squamous, erythematous lesions until the fourth postinfective week, when the intense reaction began to appear. Complete regression was observed by the fifth week in these animals. Trichophytin tests performed on the 14th day were positive in the guinea pigs of non-treated group, while negative in the PUVA-treated animals. The latter group revealed a positive reaction on the fifth week. PUVA did not show inhibitory effect on the sensitization by intracutaneous injection of trichophytin antigen. The PUVA treatment depleted the ATPase-positive Langerhans' cells. These results indicate that PUVA treatment suppresses the immunity of dermatophytosis and delays the spontaneous resolution of the lesions, and suggest that the Langerhans' cell is involved in the development of cell-mediated immunity in experimental dermatophytosis.

The effect of phototherapies on cutaneous lesions of histiocytosis X in the elderly

The effect of therapeutic ultraviolet light (UV) radiation on the skin lesions of histiocytosis X (HX) was studied in two old patients. Histiocytosis X cells in the biopsy specimens were strongly reactive with OKT-6, OK-Ia1, an anti-S-100 protein antibody, and were weakly stained with Leu-3a. Some HX cells outgrown from the explants bore immunoglobulin G receptors (Fc-IgG) and C3 receptors. In accordance with clinical improvement after repeated topical 8-methoxypsolaren (8-MOP) plus UV-A (PUVA) or UV-B radiation, the density of infiltrating HX cells gradually was decreased. The PUVA therapy seemed to be more effective than UV-B radiation in our treatment schedule. Even after repeated phototherapies, however, the reactivity of surface and cytoplasmic antigens related to OKT-6, OK-Ia1, and S-100 protein in the remaining HX cells were the same as in untreated HX cells. Although the exact mechanism remains obscure, satisfactory therapeutic results were obtained in response to the phototherapies. New skin lesions eventually recurred after cessation of the treatments, but such eruptions resolved when additional PUVA was resumed. These studies confirm that HX cells share a battery of cytologic characteristics with epidermal Langerhans' cells (LC) and that repeated phototherapies provide a beneficial effect for skin lesions of HX without adverse reactions.