INHIBITION OF CHRONIC RELAPSING EXPERIMENTAL ALLERGIC ENCEPHALOMYELITIS IN THE BIOZZI AB/H MOUSE

Chronic relapsing experimental allergic encephalomyelitis (CREAE) can be reproducibly induced in Biozzi AB/H mice following injection of spinal cord homogenate (SCH) emulsified in complete Freund's adjuvant (CFA). Active clinical disease is associated with mononuclear cell infiltration of the central nervous system (CNS), mainly the spinal cord. Whole brain homogenate (BH), however, failed to induce clinical or histological disease. In contrast, substituting sciatic nerve homogenate in the inoculum induced experimental allergic neuritis (EAN). Clinical disease was manifest earlier (13.1 +/- 0.3 days) than CREAE (16.2 +/- 1.4) and was accompanied by mononuclear infiltration of the peripheral nervous system (PNS). In comparison to CREAE induction, pretreating mice with SCH or BH in incomplete Freund's adjuvant (IFA) suppressed the development of SCH-induced disease. The BH was more tolerogenic than the SCH and this hyporesponsiveness was CNS antigen-specific as PNS tissue failed to inhibit the course of CREAE. Tolerance induced by pretreatment with SCH or BH in IFA was reversed by a single injection of 200 mg/kg cyclophosphamide, 2 days prior to CREAE induction. This suggests that IFA-induced hyporesponsiveness is actively regulated, possibly via the action of suppressor cells. In addition, treatment with neuroantigens in IFA appears to be mainly afferent acting as it serves to prevent initial disease induction. This treatment after immunization for CREAE, however, fails to prevent disease progression. Furthermore, treatment with CNS antigens emulsified in IFA during the post-acute remission stage appeared to synchronize and induce (32 +/- 1 days) the onset of clinical relapse, compared with untreated controls (41 +/- 5 days). This indicates that such IFA treatment has minimal value in controlling an ongoing immune disease of the CNS.