Retinal antigen-induced inhibition of experimental auto-immune uveoretinitis: Specific prevention and therapy of the disease

Abstract

Ethylenediamine (EDA) is reported to be a poorly characterized iatrogenic and occupational contact sensitizer. To better characterize EDA hypersensitivity, a guinea pig model was employed in which the animals were exposed epicutaneously to simulate conditions of human exposure, and selected immune parameters were measured. Induction of hypersensitivity was by the Buehler occluded patch method (6 hr application/day, once a week for 3 consecutive weeks) to 10, 20, 30, or 40% EDA, using either an ethanol or acetone/corn oil vehicle. Fourteen days after the last induction, guinea pigs were challenged by patch application of 2% EDA (nonirritating). The incidence of responders for erythema in the 10% EDA (ethanol) treatment group was 83 and 50% at 24 and 48 hr, respectively. In the 10% EDA (acetone/corn oil) group the corresponding values were 50 and 17%. For 20, 30, and 40% EDA, in either vehicle, the incidence of erythema was 83 to 100%. Severity grades (scale = 0–3) for cutaneous reactions to increasing concentrations of EDA in ethanol ranged from 0.8 to 2.5; those for EDA in acetone/corn oil ranged from 0.6 to 2.8. Using an enzyme-linked immunosorbent assay developed to detect the predominant serum antibodies to EDA, it was shown that guinea pigs treated by patch application did not produce the main allergic antibody IgG specific for EDA. However, intradermal administration of an EDA-guinea pig serum albumin conjugate (EDA-GSA) to guinea pigs presensitized by patch application resulted in antibody production by 39 and 86% of the animals, at the initial and second dosing, respectively. An in vitro blastogenesis assay, using peripheral blood lymphocytes from EDA-sensitized guinea pigs, was developed to identify specific chemical allergens implicated in in vivo sensitization. Maximum tritiated thymidine ([3H]TdR) incorporation by lymphocytes stimulated in vitro with EDA-GSA was observed on Day 7. Optimal antigen concentration for maximum lymphocyte proliferation ranged from 5 to 50 μg/ml, the major variation being attributable to interanimal differences. These results indicate that epicutaneous application of EDA in the guinea pig induces a Type IV delayed hypersensitivity; immunological memory to the hapten is maintained in cultured lymphocytes, suggesting the potential usefulness of the lymphocyte transformation test for in vitro diagnosis of chemically induced hypersensitivity in humans.