Nasal administration of soluble antigens is an exciting means of specifically down-regulating pathogenic T-cell reactivities in autoimmune diseases. The mechanisms by which nasal administration of soluble antigens suppresses autoimmunity are poorly understood. To define further the principles of nasal tolerance induction, we studied the effects of nasal administration of myelin basic protein (MBP) on experimental autoimmune encephalomyelitis (EAE) in the Lewis rat. EAE is a CD4+ T-cell-mediated animal model for human multiple sclerosis. Nasal administration of guinea-pig (gp)-MBP at a dose as low as 30 gtg/rat can completely prevent gp-MBP-induced EAE, whereas nasal administration of bovine (b)-MBP is not effective even at a much higher dosage. Cellular immune responses, as reflected by T-cell proliferation and interferon-y (IFN-y)- ELISPOT, were suppressed in rats receiving the two different doses (30 and 600 Jig/rat) of gp-MBP, but not after administration of b-MBP. Rats tolerized with both doses of gp-MBP had also abrogated MBP-induced IFN-y mRNA expression in popliteal and inguinal lymph node mononuclear cells compared with rats receiving phosphate-buffered saline nasally. However, adoptive transfer revealed that only spleen mononuclear cells from rats pretreated with a low dose, but not from those pretreated with a high dose, of gp-MBP transferred protection to actively induced EAE. Low-dose (30 Jg/rat) gp-MBP-tolerized rats also had high numbers of interleukin-4 (IL-4) mRNA-expressing lymph node cells, while high-dose (600 Jg/rat) gp-MBP-tolerized rats had low numbers of IL-4 mRNA-expressing lymph node cells. Our data suggest an exquisite specificity of nasal tolerance. Dose-dependent mechanisms also relate to nasal tolerance induction and protection against EAE in the Lewis rat.

Background and Purpose—Cerebral ischemia is associated with inflammation involving accumulation of polymorphonuclearneutrophils. T cells have been suggested to contribute to the secondary progression of ischemic braininjury. Dendritic cells (DC) are potent regulators of immunity by activating and tolerizing T cells. DC have previouslybeen detected in rat meninges and choroid plexus. Hypothesizing that DC are involved in inflammation associated withcerebral ischemia, we investigated DC in the brain of Sprague-Dawley rats after permanent middle cerebral arteryocclusion (pMCAO) versus sham operation.Methods-All experimental rats (n 24) had the right MCA permanently occluded by inserting a nylon monofilamentthrough the right external carotid artery. Immunohistochemistry was used to detect DC (OX62), microglia/macrophages (OX42) that developed into DC, and activated DC expressing major histocompatibility complex class II (OX6) in the brain hemispheres at 1 hour to 6 days after pMCAO or sham operation.Results—Levels of DC were elevated at 1 hour in the ischemic versus sham hemispheres (P 0.001) and ischemic versusnonischemic hemispheres (P 0.001). Activated DC expressing major histocompatibility complex class II(OX62 OX6 ) were still elevated at 6 days after pMCAO in the ischemic versus nonischemic hemispheres (P 0.01).The area of brain lesion correlated with numbers of OX62 DC per 100-mm2 brain tissue section (r 0.79; P 0.0001). Conclusions-Increased levels of DC inthe brain after pMCAO and correlation between DC numbers and brain lesion areaindicate a role for DC in cerebral ischemia. This observation could constitute a basis for further studies on the role ofDC in inflammation related to cerebral ischemia.

Experimental autoimmune myasthenia gravis (EAMG) is an animal model for human myasthenia gravis (MG). Autoantibody-induced functional loss of nicotinic acetylcholine receptor (AChR) at the postsynaptic membrane is an important pathogenic feature of both MG and EAMG. To evaluate the extent at which the humoral immune response against AChR operates in the pathogenesis of EAMG, we immunized B cell knockout (mMT) and wild-type C57BL/6 mice with AChR and complete Freund’s adjuvant. The ability of AChR-primed lymph node cells to proliferate and secrete IFN-g in response to AChR and its dominant peptide a146-162 were intact in mMT mice as in wild-type mice. Similar amounts of mRNA for IFN-g, IL-4 and IL-10 in AChR-reactive lymph node cells were detected in mMT and wild-type mice. However, mMT mice had no detectable anti-AChR antibodies and remained completely free from clinical EAMG. We conclude that B cells are critically required for the genesis of clinical EAMG, but not for AChR-specific T cell priming.

Tolerance to B cell-mediated experimental autoim-mune myasthenia gravis (EAMG), an animal model for myasthenia gravis (MG) in human s, can be achieved byn asal adminis tra tion of the autoantigen acetylcholin ereceptor (AChR). Nasal tolerance induction requiresonly l/1000 0f the amount of AChR used for oral toler-ance in ductio n, but is as effe ctive in preventing EAMG.To investigate whether nasally induced tolerance toEAMG can be inOuenced by nasal administration ofcytokin es, recom bin ant rat IFN -y (total 5000 U/ra t), acombination of AChR and IFN-'y or AChR alone was given nasally to Lewis rats before immunization withAChR and complete Freun d's adjuvant (CFA). One ad-ditional group of rats received the same amount ofAChR nasally in conjunction with IFN-y (total5000 Ulrat) intraperitoneally. AChR given alone nasally in-duced effective tolerance to EAMG whereas rats re-ceiving AChR + IFN-y by the nasal route exhibited asimilar disease pattern, and similarly escalated T andB cell responses to AChR when compared to controlEAMG rats. In contrast, administration of IFN-y ip to-gether with AChR nasally did not affect the inductionof tolerance to EAMG. IFN-'y given alone nasally didnot affect clinic al EAMG. This study demonstrates th at nasal tolerance can be modulated by nasal administra-tion of minute amounts of IFN- y. Nas al adminis trationof certain cytokines with benemial effects mightbroaden the effectiveness of applying nasal toleranceas a poten tial therapeu tic means of preventing au toim-mune diseases..

Tumor necrosis factor receptor-1 (TNFR1, CD120a) has been implicated in the pathogenesis of several experimental models of T cell-mediated autoimmune disorders, but its role in antibodymediated autoimmune diseases has not been addressed. Experimental autoimmune myastheniagravis (EAMG), an autoantibody-mediated T cell-dependent neuromuscular disorder, representsan animal model for myasthenia gravis in human. To investigate the role of TNFR1 in thepathogenesis of EAMG, TNFR1-/- and wild-type mice were immunized with Torpedo acetylcholinereceptor (AChR) in complete Freund's adjuvant. TNFR1-/- mice failed to develop EAMG. Lymphoidcells from TNFR1-/- mice produced low amounts of Th1 (IFN-γ, IL-2 and IL-12)-type cytokines, butelevated levels of Th2 (IL-4 and IL-10)-type cytokines compared with lymphoid cells of wild-typemice. Accordingly, the levels of anti-AChR IgG2 antibodies were severely reduced and the level ofanti-AChR IgG1 antibodies were moderately reduced. Co-injection of recombinant mouse IL-12 withAChR in adjuvant restored T cell responses to AChR and promoted development of EAMG inTNFR1-/-mice. These results demonstrate that the TNF/TNFR1 system is required for thedevelopment of EAMG. The lack of a functional TNF/TNFR1 system can, at least in part, besubstituted by IL-12 at the stage of initial priming with AChR and adjuvant. Introduction.