Tissue sections from diseased skin of sixteen patients with atopic dermatitis were investigated with haematoxylin-eosin and toluidine-blue staining, with direct immunofluorescence staining using FITC-conjugated antisera against IgG F(ab')2 and IgM, and with the indirect immunofluorescence method utilizing specific rabbit anti-human T lymphocyte antiserum with FITC-conjugated goat anti-rabbit Ig antiserum as the second layer. Furthermore, cryostat sections were investigated in a closed chamber immune adherence method using aminoethylisothiouronium bromide (AET) treated sheep red blood cells to detect E receptors on T lymphocytes, and with various types of coated sheep red blood cells to detect cells with IgG Fc receptors and complement factor C3b receptors. All sections presented dermal perivascular infiltrates of mononuclear cells as judged by haematoxylin-eosin staining. Staining with toluidine-blue demonstrated varying numbers of mast-cells, but in no case pathological increased number. The majority of the infiltrating cells presented rim-like membrane fluorescence with the anti-T antiserum, and the AET treated sheep red blood cells (SRBC) adhered to the infiltrates, thus indicating a predominance of T lymphocytes in the skin infiltrates of atopic dermatitis.

The patient group consisted of 18 elderly male patients with persistent light reactivity who were subjected to extensive phototesting with different wavelengths, including patch and photopatch testing. All reacted adversely to ultraviolet light and some also to longer wavelengths when tested on normal appearing skin. 17 patients showed contact or photocontact reactions, of which 12 were positive photopatch test reactions and 11 were plain contact reactions. Contact allergy to constituents of oak moss and different lichen compounds was twice as common as allergy to Compositae oleoresins. 72 patients with chronic polymorphic light eruption were used as a control group. 10 of these patients had either a positive photopatch test reaction or a plain contact allergy. Patients with persistent light reactivity are characterized by a particular susceptibility to develop a delayed-type hypersensitivity. They frequently have both photo and plain contact allergy, often to substances used in cosmetics. In 13 of 16 patients in whom a biopsy was carried out, the histology supported the clinical diagnosis. In none of the biopsies was the picture diagnostic in itself. This underlines the inadequacy of light microscopy as the only diagnostic procedure.

Thirty lightly pigmented hairless (Hr/Hr) mice were irradiated 5 days per week for 30 weeks to assess the photocarcinogenicity of a new Philips TL 01 narrow-band (311 nm +/- 2) UVB lamp. All mice were found to be tumour-bearing after 16 weeks and histologically, 83% of these had definite squamous cell carcinomas. Compared with our previous study where conventional broad-band Philips TL 12 UVB irradiation was used, tumours appeared earlier with the TL 01 lamp. The total irradiation dose was, however, several times greater in the TL 01 assay while the total MED dose was considerably less.

Photocarcinogenesis was induced in 90 lightly-pigmented hairless mice using a Philips Tl 40 W/12 light source which emits mainly UVB (290-320 nm). During one-third of the induction period (weeks 16-26) a group of 30 mice were protected by topical para-aminobenzoic acid (PABA) and then irradiated again without protection up to week 30 and observed for a further 10 weeks. The application of PABA resulted in a significant delay (p less than 0.05) in tumour induction and discontinuation of PABA caused an abrupt decline in the number of tumour-free animals. At the end of the study there was a significant difference in the yield of carcinomas for the PABA group, 20, compared with 78 for non-protected mice (p less than 0.05). There was also a statistically significant difference (p less than 0.05) between the weight of dorsal skin in non-protected mice compared with the PABA-protected group, the latter showing no difference from a control group of non-irradiated mice. The proportion of benign tumours in the PABA group was significantly (p less than 0.05) higher than in the non-protected group, suggesting an inhibition of the photo-carcinogenic process.