Assessment of occupational exposure and spectrum of contact sensitization in metalworkers with occupational dermatitis: results of a cohort study within the OCCUDERM project.

BACKGROUND: Metalworkers occupationally exposed to metals, tools, metalworking fluids (MWFs), technical oils, gloves, skin care products etc. frequently suffer from occupational dermatitis (OD). OBJECTIVES: To investigate occupational exposure and to identify relevant occupational sensitizers in metalworkers with OD, and to evaluate suitability of current German patch test recommendations for this occupational group. PATIENTS AND METHODS: As part of the OCCUDERM project, occupational exposure of 230 metalworkers with suspected OD patch tested in the departments of dermatology in Göttingen and Osnabrück (both Lower Saxony, Germany) in 2012-2017 was recorded by questionnaire. These data, as well as results, of patch testing with standardized allergens and with workplace material were analysed. RESULTS: Metalworking fluids and skin care products were the most important exposures. Among MWF allergens, most frequently sensitizations to formaldehyde and formaldehyde releasers, colophony/abietic acid and monoethanolamine were observed. Sensitization to methylisothiazolinone (MI) was frequent, probably as part of the general European epidemic of contact allergy to MI in leave-on cosmetics. Sensitization to glove ingredients only played a minor role. CONCLUSIONS: The known occupational allergen spectrum could largely be confirmed. In order not to miss relevant sensitizations, patch testing with material from the patients' workplaces in parallel to baseline and MWF series is recommended. Sensitizations diagnosed could not always be linked to particular occupational exposures.

Properties of the carcinoma-associated antigen MH 99/KS 1/4 in normal and transformed human keratinocytes: regulation of synthesis, molecular cross-linking and ultrastructural localization.

A 38-kDa cell-surface glycoprotein defined by monoclonal antibody MH 99 is markedly increased in many epithelial tumours. In normal human skin, it is a characteristic marker for germ-cell phenotypic tissues. Although the gene encoding the MH 99 antigen has recently been cloned, and several histological and biochemical studies have been performed, the biological function of this interesting antigen still remains unknown. In the present study, we examined the synthesis of MH 99 in keratinocyte populations showing different in vitro differentiation capacity. Normal keratinocytes, spontaneously immortalized keratinocytes (cell line HaCaT), three SV-40-transformed keratinocyte lines (130, 425, and HaSV), and two squamous cell carcinoma lines (SCL-1 and SCL-2), were compared. Radioimmunoprecipitation revealed the highest levels of synthesis in cell populations with the least differentiation. This was paralleled by an increase of MH 99 synthesis in normal keratinocytes cultured in low concentrations of Ca2+ and by an increase of MH 99 synthesis during subculture of normal keratinocytes. Both phenomena were paralleled by an opposite behaviour of a differentiation marker. Molecular cross-linking and subsequent immunoprecipitation led to a decrease of the MH 99 signal, but an increase of a high molecular weight protein signal was seen. After cleavage of the crosslinker, the MH 99 signal reappeared, whereas the signal of the large protein remained unchanged. Thus, the MH 99 antigen may be associated with a high molecular weight protein on the cell surface, supporting the suggestion of a receptor-like function. Phosphorylation of the molecule could not be detected. Immunoelectron microscopy revealed homogeneous distribution on the cell surface, but cells of the same culture exhibited clear differences in their MH 99 expression. A concept for MH 99 regulation in normal and transformed human keratinocyte populations in vitro is proposed, showing that the synthesis of MH 99 is inversely correlated with cell differentiation. The association with a high molecular weight protein supports the suggestion that the MH 99 antigen interacts with other molecules.

The human hair follicle: glycoprotein-related antigenic profile of distinct keratinocyte populations in vivo and their alterations in vitro.

The cell surface expression of three glycoprotein antigens, as defined by the monoclonal antibodies BT 15, T 43, and MH 99, was investigated in follicular keratinocyte populations in vivo. In addition, the regulation of glycoprotein synthesis was studied in follicular and interfollicular keratinocytes cultured in vitro. The BT 15 antigen was strongly expressed in the inner root sheath and the area above Auber's line of the hair bulb, whereas the T43 antigen was mainly seen in the outer root sheath. Selectively high expression of the MH 99 antigen was found only in outgrowing germ buds of early anagen follicles. Radioimmunoprecipitation revealed strong signals with BT 15 in freshly prepared follicular keratinocytes, two to three times stronger than those in interfollicular keratinocytes, but the signals clearly decreased by 80% under continuing culture conditions. The T 43 antigen was found by FACS analysis and radioimmunoprecipitation in initially low amounts in both populations, but the signals increased dramatically (up to 50 times) in long-term cultures and in subcultures. The MH 99 antigen was also initially present only in low amounts, in interfollicular rather than in follicular keratinocytes, but its expression increased up to 15-fold with continuing culture and any differences between the two populations disappeared. Our investigation revealed that at least three populations of hair follicle keratinocytes are characterized by different surface glycoprotein antigens, clearly related to their state of differentiation and proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)

Carcinoma-associated 38-kD membrane glycoprotein MH 99/KS 1/4 is related to proliferation and age of transformed epithelial cell lines.

A 38-kD cell-surface glycoprotein (MH 99, KS 1/4) appears strongly elevated in epithelial malignancies, although it also occurs in a few immature, germ-cell phenotypic tissues in human epidermis. In this study, the expression and synthesis characteristics of the MH 99 antigen were examined in several transformed epithelial cell lines. Marked increase of MH 99 (by 100-200%) was found in highly proliferative cell populations, as demonstrated by radioimmunoprecipitation, fluorescence-activated cell sorter analysis, and proliferation experiments in cultures of spontaneously immortalized keratinocytes (HaCaT) squamous cell carcinoma lines (SCL 1 and SCL 2), and SV-40 transformed keratinocytes (130, 425, and HaSV). The relation of the MH 99 antigen to cell proliferation was underscored by a 70-75% decrease of synthesis in nonproliferating HaCaT cells treated with mitomycin C. Blocking of two distinct epitopes of the molecule with two different monoclonal antibodies (MH 99 and MM 104) decreased cell proliferation by approximately 25% (F = 519.6; df = 1,145; p < 0.0001), as compared to untreated cells and to cells treated with unrelated antibodies (BT 15 and J 143). Analysis of MH 99 synthesis in aging transformed keratinocytes cultured without passage revealed downregulation by approximately 50-60% after 60 d, indicating inverse correlation of the MH 99 antigen with increasing cell age. It seems, therefore, that the MH 99 antigen is directly correlated with cell proliferation and inversely correlated with increasing age of transformed epithelial cells, possibly playing an active role in the process of cell proliferation.