IMMUNOHISTOCHEMICAL STUDY OF CUTANEOUS NEURITIS IN POSITIVE LEPROMIN REACTIONS

Sixty skin biopsies taken from positive tuberculoid and borderline-tub erculoid late lepromin reaction were studied using histological techni ques. The distribution of mycobacterial antigen and nerves was demonst rated using immunochemical methods. A total of 557 nerve bundles was o bserved in 51 biopsies; 9 were devoid of nerves in the sections examin ed; 475 nerve bundles showed some relationship to the inflammatory inf iltrate (85%); perineuritis being seen in 144 (30%) and endoneuritis i n 5 (0.9%). Mycobacterial antigens inside the granuloma were detected in 59 of the 60 biopsies (98%). Only one specimen, showing a strong tu berculoid reaction, failed to show these antigens. On the contrary, my cobacterial antigen was absent in almost all nerves. Small deposits we re detected in the perineurium of one nerve with perineuritis, and ins ide a Schwann cell of another, the latter belonging to a previously mu ltibacillary patient. The neurotropic tendency of the granuloma does n ot seem to be stimulated by the presence of mycobacterial antigens ins ide the nerves, as normally these antigens do not penetrate them. The hypothesis of some antigenic fraction of the neural tissue which cross -reacts with Mycobacterium leprae antigens, thus eliciting a perineura l or near-perineural inflammatory reaction is put forward, but needs f urther investigation.