Epidermal Langerhans cell apoptosis is induced in vivo by nonanoic acid but not by sodium lauryl sulphate.

Exposure to irritants may cause chronic irritant contact dermatitis (ICD), characterized by irregular epidermal thickening and a predominantly dermal mononuclear cell infiltrate. The mechanisms involved, and why only certain individuals are affected, are not clearly understood. Different irritants may trigger different cellular and molecular interactions between resident skin cells and recruited inflammatory cells. In some individuals these interactions may become self-perpetuating resulting in persistent inflammation in the absence of continued exposure. This study examined Langerhans cell (LC) density in clinically normal skin of 46 patients with chronic ICD and 10 healthy individuals, and compared the action of the two irritants nonanoic acid (NA) and sodium lauryl sulphate (SLS) on the LCs and keratinocytes of clinically normal skin in patients with chronic ICD. There was a higher number of LCs/mm basement membrane in patients compared with controls, although there was no difference in the number of dendrites/LC nor in dendrite length. SLS induced keratinocyte proliferation after 48 h exposure, had no effect on LC number or distribution, and induced keratinocyte apoptosis after 24 and 48 h exposure. In contrast, NA decreased keratinocyte proliferation after 24 h exposure but this returned to basal levels after 48 h, and induced epidermal cell apoptosis after only 6 h exposure. NA dramatically decreased LC number after 24 and 48 h exposure, which was accompanied by basal redistribution and decreased dendrite length. Most significantly, NA induced apoptosis in over half of the LCs present after 24 and 48 h exposure.

Epidermal keratinocyte production of interferon-gamma immunoreactive protein and mRNA is an early event in allergic contact dermatitis.

Previous work has indicated the importance of cytokine cascades in the induction of contact dermatitis, but there is little information on the cellular localization of cytokines in human skin, particularly during the early phases of the inflammatory response to contact allergens. Using in situ hybridization for mRNA and immunocytochemistry on biopsies from a series of 16 patients with known allergic contact dermatitis, we examined the kinetics of early cytokine production after challenge with relevant or irrelevant antigen. We show that epidermal keratinocytes from patients challenged in vivo with allergen, but not irrelevant antigen, rapidly synthesize (within 4 h) mRNA for interferon-gamma and produce immunoreactive interferon-gamma. Interleukin-1alpha and interleukin-8 mRNA were also detected but showed no correlation with relevant antigen challenge. This study demonstrates that keratinocytes can produce interferon-gamma and that this production is linked to challenge with relevant antigen in allergic contact dermatitis. These findings indicate that keratinocytes may amplify allergen-specific T-lymphocyte-triggered interferon-gamma dependent responses and might partially explain the speed of reaction in this common disease and other delayed hypersensitivity reactions involving the skin.

Topical diphencyprone for alopecia areata: evaluation of 48 cases after 30 months' follow-up.

Forty-eight patients (23 male, 25 female) with severe alopecia areata were sensitized and treated with topical diphencyprone. Thirty-eight per cent of the subjects had good regrowth of hair at a mean follow-up period of 30.8 months. The presence of nail changes, a personal history of atopy and a long duration of alopecia had an adverse prognostic effect.

Changes in skin pH after the use of baby wipes.

We recently made a double-blind safety-in-use comparison of four different brands of baby wipes using a panel of 302 infants over a period of 10 weeks. For the first two weeks, only soap and water was used to clean the babies' skin after each diaper change, and then for the eight-week test phase each baby was allocated one or other of the products for normal home use. The wipes differed in cleansing lotion formulation (emollients, preservative, pH) and fibrous composition. There were no clinically detectable differences in the effects of the wipes in terms of erythema, frequency of rashes, edema, and desquamation, but we recorded significant changes in the pH of pubic and buttock skin inside the diaper area. In particular, the brand of wipes with the lowest pH (2.8) in the lotion reduced the mean skin pH from 5.6 to 5.0 (p < 0.01), and those with a pH of 5.5 had no significant effect. Wipes of intermediate pH (3.7) gave a final skin pH of 5.4-but the downward trend was not statistically significant. These data indicate that skin pH can be depressed by such topical application, although the trial lasted only a fraction of the total time wipes might be used on each infant. Further research is necessary to evaluate the implications of these findings.

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.

A non-radiolabelled in situ hybridization method for the detection of epidermal cytokine mRNA.

We describe a non-radiolabelled method for the in situ detection of epidermal cytokine mRNA in paraffin sections of skin biopsies from sites of nickel contact sensitivity. The method uses fluorescein isothiocyanate-labelled oligonucleotide exon probe cocktails.

Isolated basal keratinocytes express pemphigoid gestationis antigen.

Basal keratinocytes were isolated from epidermal cell suspensions prepared by trypsinization of normal human skin. Cells were identified as basal cells by their adherence to collagen and confirmed as basal cells by the presence of pemphigoid antigen. Using an indirect immunofluorescence assay, cells were found to express pemphigoid gestationis-related antigen. Sera from patients with pemphigoid gestationis reacted in one of two immunofluorescence patterns: either polar, in a pattern similar to that observed with bullous pemphigoid serum, or with uniform staining around the cell periphery. Pemphigoid gestationis-related antigen is expressed by isolated basal keratinocytes and is resistant to trypsinization. The heterogeneity of immunofluorescence patterns may correspond to the heterogeneity of antigen recognition by different patients with pemphigoid gestationis.

An immunophenotypic study of lichen nitidus.

Skin biopsies from three patients with lichen nitidus were studied using a battery of monoclonal antibodies against cells in the dermal infiltrate. In each case the findings were identical with a marked excess of CD4+ cells over CD8+ cells and the presence of large numbers of CD1+ cells. These results are very similar to those seen in lichen planus reinforcing the association between these two conditions.

Dermatitis due to intravesical mitomycin C: a delayed-type hypersensitivity reaction?

Mitomycin C is an alkylating agent, used by intravesical instillation to treat carcinoma of the bladder. Repeated instillations can induce cystitis and an eczematous eruption affecting the palms, soles and face. If these effects are due to delayed hypersensitivity with sensitization to mitomycin C occurring in the bladder wall, it should be possible to demonstrate antigen-presenting cells in the bladder wall and positive patch tests to the drug. Using an immuno-alkaline phosphatase method we have identified CDI+ cells in bladder epithelium and submucosa and have demonstrated Birbeck granules in a few cells. In further support of our hypothesis it was also possible to demonstrate delayed type hypersensitivity in 13 out of 26 patients who had received mitomycin instillations by applying the allergen as a patch test. These results indicate that the eczematous eruption in this group of patients is most likely a hypersensitivity reaction and that it may be mediated transvesically.

Immunophenotyping of the eczematous flare-up reaction in a nickel-sensitive subject.

An eczematous flare-up reaction, occurring at a previously involved site, which followed oral challenge with 5.6 mg of nickel in a 29-year-old nickel-sensitive woman, was biopsied and studied by immunohistochemistry. The cellular infiltrate in the dermis and epidermis at 8 days was predominantly of Leu 3a phenotype (helper/inducer T lymphocytes), with smaller numbers of Leu-2a-reactive (suppressor/cytotoxic) T lymphocytes. Many infiltrating cells were DR-positive. No increase in epidermal Leu-6-positive Langerhans cells was seen but Leu-6-reactive cells were noted in the dermal infiltrate. Keratinocytes showed some expression of class II antigen (mainly DR). In comparison with the 48-hour allergic patch test reaction, the eczematous flare-up site showed no increase in epidermal Langerhans cell numbers nor infiltration with macrophages, but the responses were similar since both showed a superficial T cell reaction in the skin.

Keratinocyte expression of MHC class II antigens in allergic sensitization and challenge reactions and in irritant contact dermatitis.

Keratinocytes expressed major histocompatibility complex class II antigens during the development of irritant contact dermatitis, and during the induction of contact hypersensitivity, as well as in established allergic contact dermatitis. A battery of anti-class II monoclonal antibodies, some of which are specific for class II subregion products (DP, DQ, DR), was used in an immunohistochemical study of the sequential changes in the allergic challenge reactions to dinitrochlorobenzene (DNCB) and nickel, the irritant response to anthralin, and the induction of sensitization to DNCB. The induction of keratinocyte class II expression paralleled the influx of Leu-3a+ T cells into the skin and had occurred by 24 or 48 h in each type of reaction. Differential expression of class II subregion products on keratinocytes was noted: DR was the most frequently expressed molecule, followed by DP and DQ, although in the irritant response, DP expression was not observed. The importance of these observations can be decided only by functional studies.

Phenotypic characterization of the early cellular responses in allergic and irritant contact dermatitis.

Despite qualitative similarities there were subtle differences between the nickel allergic and dithranol irritant dermatitis reactions. In both responses, dermal and epidermal cellular infiltrates developed, which were predominantly of Leu 3a phenotype with lesser numbers of Leu 2a positive cells. Dermal infiltrates were larger in the allergic response, but epidermal invasion was greater in the irritant reaction. In the allergic challenge response, Leu 3a reactive cells appeared in the dermis and epidermis by 4 h. At 48 h, both reactions showed skin infiltration by Leu M3 positive macrophages, and had increased numbers of cells in the epidermis expressing class II antigens. The number of Leu 6 reactive Langerhans cells in the epidermis was almost halved at 48 h in the irritant reaction, but Langerhans cell counts were increased by a third between 24 and 48 h of the allergic response. Ultrastructural studies showed disruption of the Langerhans cell mitochondrial cristae at 8 h in the irritant reaction, with few identifiable epidermal Langerhans cells at 48 h. At 1 h in the allergic response, electron microscopy identified two populations of Langerhans cells; the majority showed an electron-dense cytoplasm with vacuoles, and the rest appeared normal. Peripolesis was noted in both types of reaction.

MHC class II antigen expression in normal human epidermis.

Monoclonal antibodies consistently demonstrated the presence of MHC class II antigens (HLA-DR,-DP and -DQ) on keratinocytes in normal human epidermis. Reactivity was normally greatest on the keratinocytes of the intraepidermal portion of sweat ducts or the external root sheath of hair follicles, but staining was noted on the surface of some interappendageal keratinocytes in most subjects. The patterns were varied but distinctive and depended on the antibody used. The functional importance of the MHC class II antigens expressed on normal keratinocytes remains to be investigated.

Early cellular reactions induced by dinitrochlorobenzene in sensitized human skin.

Serial biopsies during the first 24 hours after dinitrochlorobenzene (DNCB) challenge in fifteen sensitized patients have shown that DNCB associates with Langerhans cells within I hour of application, and has reached the dermis around the appendages by 6 hours.