Failure to induce tolerance to mechlorethamine hydrochloride.

In view of the contradictory results reported in the literature regarding induction of specific immunologic tolerance to mechlorethamine hydrochloride (HN2), the problem was reinvestigated using a "tolerogenic" schedule that had been reported to be effective. Mechlorethamine hydrochloride, 200 microgram, intravenously, was given weekly for five weeks before beginning topical therapy with it. In the test group, five of 13 patients (11 with mycosis fungoides and two with psoriasis) became contact sensitized to mechlorethamine. In another patient, what was probably a contact urticarial reaction developed. In the control group, five of 13 patients (12 with mycosis fungoides, one with parapsoriasis) became contact sensitized to mechlorethamine. Thus, 38% of the patients in both groups became contact sensitized to mechlorethamine. It is concluded that this tolerogenic schedule, just as others previously tried, was not effective in inducing specific tolerance to mechlorethamine.