Induction of contact sensitivity and antigenic competition by the intravenous administration of contact sensitizers.

The effect of route of administration of contact sensitizers on the induction of antigenic competition between dinitrofluorobenzene (DNFB) and picryl chloride (PCl) and between oxazolone (Ox) and PCl was investigated. Antigenic competition (depressed contact sensitivity to PCl) was induced not only by painting with DNFB via various routes, such as intravenous (i.v.), oral or subcutaneous routes. Antigenic competition was abolished by the treatment with cyclophosphamide (CY) 4 days after i.v. injection of competing DNFB or Ox, and also by thymectomy 6 weeks prior to the injection of DNFB. These results suggest that thymus-derived suppressor cells may be involved in the antigenic competition induced by the i.v. injection of DNFB. Primary contact sensitivity (CS) was induced by painting of DNFB or Ox and also by i.v. injection of Ox. Although an i.v. injection of DNFB into normal mice did not induce CS, it induced a strong CS in the mice pretreated with CY 2 days prior to the injection of DNFB. Examination on the effect of dose of contact sensitizers on the induction of antigenic competition, primary CS and tolerance by painting or by i.v. injection of DNFB or Ox showed that the degree of antigenic competition has a closer relationship with CS, than with unresponsiveness.