Sensitization, Immunological Tolerance and Desensitization of Guinea Pigs to Neoarsphenamine III.

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Abstract
A specific and complete immunological tolerance to neoarsphenamine (NEO) lasting for 8 to 12 months was Induced in adult guinea pigs by a single intravenous injection performed 3 to 4 weeks before the sensitizing attempt consisting in an intradermal injection of the same compound. Whereas the development of NEO hypersensitivity appeared to depend on the NEO lot and the diet, tolerance to NEO was obtained quite regularly whatever the NEO lot used and the diet fed. In contrast to what-had been observed with dinitrochloro-benzene, the time interval elapsed between the tolerogenic injection of NEO and the sensitizing attempt had little if any effect on the induction of tolerance, even when intervals as long as 1 yr. were considered. However, the induction of tolerance and the duration of the tolerant state were found to be proportional to the Injected tolerogenic dose. NEO solutions ''oxidized'' by standing were as capable of inducing tolerance as freshly prepared solutions. The state of tolerance could not be terminated by repeated weekly intradermal injections of NEO emulsified In Freund''s complete adjuvant. Tolerance to NEO was also induced by other aromatic arsenicals, trivalent arsenicals being more efficient than pentavalent arsenicals.