SUMMARYFrom anitnal studies we know that oral administration of T-dependent antigens before sensitization effectively induces systemic immune iinresponsiveness. Such 'oral tolerance" is persistent, dosedependent, antigen-specific and presumably T suppressor cell-mediated. Oral tolerance induction could be an effective way to prevent undesired T cell-mediated immune functions, sueh as playing a role in altograft reaciion, autoimmune and allergic diseases. In the present study allergic eontaet hypersensitivity (ACH) to nickel, currently presenting the most frequent contact allergy in man. was chosen to establish the feasibility of oral prevention of undesired T cell-mediated immunity in man. Potentially tolerizing {oral nickel contacts via orthodontic braces) as well as sensitizing (ear piercing) events were studied retrospectively in 2176 patients attending nine European patch test clinics. Patients were interviewed by means ofa confidential questionnaire. The results show that ear piercing strongly favoured development of nickel ACH. More importantly, patients having had oral contacts with nickel-releasing appliances (dental braces) at an early age, but only if prior lo ear piercing, showed a reduced frequency of nickel hypersensitivity. Frequencies of other hypersensitivities, in particular to fragrance, were not affected. These results support our view that induction of specific systemic immunologic tolerance by timely oral administration of antigens is feasible in man.

We detected significant clinical and tissue differences between agents, providing a novel approach to study the differential effects of topical formulations using a limited sample size.

During a 15‐month period. 536 patients being investigated for suspected contact dermatitis were paid) tested with the European standard series and palladium chloride 1% pet, 13 patients (2.4%) had a positive allergic response to palladium chloride and all 13 were also allergic to nickel. 12 of these 13 patients consented to further patch testing with discs of pure palladium metal Toil, mid none reacted. We have shown previously that palladium chloride patch test material contains traces of nickel, and propose an explanation for these results in terms of the additive effect of allergens when tested in combination.

A non-insulin dependent male diabetic is reported with subcorneal pustular dermatosis associated with intraepidermal IgA deposits and a benign IgA paraproteinaemia. Treatment with dapsone and etretinate was reasonably effective, but etretinate had to be discontinued due to the development of diffuse idiopathic skeletal hyperostosis. His subcorneal pustular dermatosis subsequently flared and was troublesome for 2 years until he was commenced on PUVA, with excellent response.

The keratinocyte expression of class II MHC antigens HLA-DR, DP and DQ was studied in 20 long-lasting allergic patch test reactions and 17 normal allergic patch tests reactions. No significant difference in the expression of these antigens in the 2 groups was detected. No 1 allergen was responsible for the majority of long-lasting allergic patch test reactions. The immunological mechanisms which may contribute to long-lasting allergic patch test reactions are discussed with reference to HLA-DR keratinocytes.