INDUCTION OF INTERFERON-GAMMA, INTERLEUKIN-4, AND TRANSFORMING GROWTH-FACTOR-BETA IN RATS ORALLY TOLERIZED AGAINST EXPERIMENTAL AUTOIMMUNE MYASTHENIA-GRAVIS

Oral administration of nicotinic acetylcholine receptor (AChR) to Lewi s rats prior to myasthenogenic immunization with Torpedo AChR + comple te Freund's adjuvant (CFA) results in the prevention of experimental a utoimmune myasthenia gravis (EAMG) and the suppression of AChR-specifi c B cell responses and counteracts the development of AChR-reactive in terferon-gamma (IFN-gamma) secreting T cells. To study the involvement of the T helper type 1 (Th1) cell-related lymphokine IFN-gamma, the T h2 cell-related interleukin-4 (IL-4), and transforming growth factor b eta (TGF-beta) that suppresses the synthesis of IFN-gamma and IL-4, we used in situ hybridization with complementary DNA oligonucleotide pro bes to enumerate mononuclear cells (MNC) expressing mRNA for the cytok ines IFN-gamma, IL-4, and TGF-beta. Upon in vivo recognition of AChR, popliteal, inguinal, and mesenteric lymph nodes, spleen and thymus of rats with EAMG contained higher levels of IFN-gamma, IL,-4, and TGF-be ta mRNA-expressing cells compared to CFA-injected control rats, implic ating the involvement in EAMG of AChR-reactive Th1 and Th2 cells in pa rallel. TGF-beta was also upregulated in EAMG. Oral tolerance to EAMG was characterized by suppression of the levels of MNC expressing IFN-g amma and IL-4, but augmentation of cells expressing TGF-beta. The resu lts suggest that IFN-gamma, IL-4, and TGF-beta are involved in the dev elopment of EAMG, and that TGF-beta is important in the induction of o ral tolerance to EAMG. (C) 1994 Academic Press, Inc.