The role of lymphocyte subpopulations in the transfer of rat EAE

Relapsing and remitting experimental autoimmune encephalomyelitis in B cell deficient mice

Experimental autoimmune encephalomyelitis (EAE) is an animal model for the human autoimmune central nervous system (CNS) disease multiple sclerosis (MS). To examine the role of B cells in EAE with a relapsing and remitting disease course (R-EAE) we generated (B10.PL x SJL/J)F1 mice deficient in B cells by disrupting their mu heavy chain transmembrane region (B10.PL x SJL/J)F1 muMT-/-. By immunizing (B10.PL x SJL/J)F1 and (B10.PL x SJL/J)F1 muMT-/- mice with the encephalitogenic N-terminal peptide Acl-11 of myelin basic protein (MBP), we observed that B-cell deficient mice exhibited a relapsing and remitting disease course. Since a similar day of onset and day of first relapse were observed these data suggest that B cells do not play a vital role in the activation of T cells leading to the initiation of EAE, nor in the reactivation of T cells resulting in R-EAE.

Suppression of experimental allergic encephalomyelitis by intraventricular administration of interferon-gamma in Lewis rats

Experimental allergic encephalomyelitis (EAE) is an autoimmune inflammatory disease of the central nervous system (CNS) which causes paralysis. Several studies have reported the involvement of Ia antigen-expressing cells in the pathogenesis of EAE. Interferon-gamma (IFN-gamma) can induce Ia antigen expression on a wide range of cells. We examined the effect of IFN-gamma on EAE in Lewis rats. Systemically administered IFN-gamma did not change the disease course of EAE, whereas IFN-gamma applied locally into the ventricular system of the CNS resulted in complete suppression of clinical signs. Furthermore, we found that systemic administration of anti-IFN-gamma just prior to the onset of clinical symptoms resulted in a more severe disease course. We conclude that IFN-gamma is capable of exerting a suppressive action in EAE, possibly through induction of Ia antigen expression or through the induction of suppressive mechanisms locally in the CNS.

The adoptive transfer of chronic relapsing experimental allergic encephalomyelitis with lymph node cells sensitized to myelin proteolipid protein

In this report we describe the transfer of chronic relapsing experimental allergic encephalomyelitis (EAE) with in vitro-stimulated lymph node cells (LNC) from SJL/J mice immunized with human myelin proteolipid protein (PLP). No additional immune enhancing procedures were applied in the transfer recipients. Clinical and histological EAE was transferred with 10-30 X 10(6) LNC to 27/28 mice. The LNC proliferated in vitro to PLP, but not to myelin basic protein (MBP), and induced delayed-type hypersensitivity. Enrichment for lymphoblasts by Ficoll centrifugation was essential for the disease development. The clinical course usually showed an early episode of acute paralytic illness, followed by chronic relapsing disease, and resembled the transfer of EAE using MBP-specific cells, both clinically and histologically.

Immune mechanisms in the pathogenesis of demyelinating diseases

The loss of myelin which characterises many human and experimental demyelinating diseases, among them multiple sclerosis, is thought to be immune mediated, but the precise mechanisms responsible remain unknown despite intense research. Normally, myelin in the central nervous system (CNS) is protected from systemic immune responses by the blood brain barrier, which separates nervous tissue from the peripheral circulation. Here we review evidence suggesting that an understanding of the demyelinating disorders may be helped by considering their immune pathogenesis in two stages. The first is damage to the blood brain barrier; this appears to be cell mediated, and allows infiltration into the CNS of other immune effectors. These include complement and also macrophages, which together may mediate the second stage, injury to the myelin/oligodendrocyte complex.

Induction of Ia molecules on brain endothelium is related to susceptibility to experimental allergic encephalomyelitis

We have examined the responses of brain endothelium from different rat strains to interferon-gamma (IFN-gamma) which induces expression of MHC class II molecules. There is a marked difference between the strains in the sensitivity of their endothelium to MHC induction. LEW and DA rats, which are susceptible to experimental allergic encephalomyelitis (EAE) can be induced to express higher levels of class II molecules than EAE-resistant strains. In both the EAE-susceptible and -resistant strains, RT-1B locus-encoded molecules occur at higher surface densities than RT-1D locus molecules. These findings support the theory that genes controlling the induction of MHC expression affect disease susceptibility.

Experimental allergic encephalomyelitis in the absence of a classical delayed-type hypersensitivity reaction. Severe paralytic disease correlates with the presence of interleukin 2 receptor-positive cells infiltrating the central nervous system

One characteristic of experimental allergic encephalomyelitis (EAE) in all species is the presence of a considerable leukocyte infiltrate in the central nervous system (CNS). By adoptive transfer of EAE into irradiated or nonirradiated Lewis strain rats we now show that the bulk (greater than 90%) of infiltrating cells in the CNS are superfluous to the induction of disease, as lethally irradiated recipients, despite having very few infiltrating cells in the CNS, acquire severe paralytic EAE. The reduction in the level of infiltration in irradiated recipients is selective, however, as both irradiated and nonirradiated diseased animals have very similar numbers of cells expressing IL-2-R. Disease in irradiated recipient animals is associated with substantial submeningeal hemorrhage in the spinal cord and brain stem and similar hemorrhages are found in recipients rendered leukopenic with cytotoxic drugs. Clinical signs of disease and hemorrhage are preventable, however, by administration to the recipient rats of mAbs specific for the CD4 antigen. Classic delayed-type hypersensitivity (DTH) reactions are transferable with the same cells that produce EAE in both irradiated and nonirradiated recipient rats, but such transfer of DTH is observed only in nonirradiated recipient animals and not in irradiated rats. Collectively, the findings reported herein support the conclusion that the paralysis characteristic of acute EAE is mediated by the direct action of very small numbers of activated CD4+ lymphocytes that infiltrate the CNS and produce their effects by inducing vascular damage. The findings are not consistent with reports that the lesions in EAE are produced by a classic DTH reaction.

Antibodies against I-A and I-E determinants inhibit the activation and function of encephalitogenic T-lymphocyte lines

Two monoclonal antibodies, OX-6 and OX-17, were used to evaluate respectively the roles of I-A and I-E major histocompatibility complex Class II gene products in the in vitro activation and subsequent function in recipient rats of encephalitogenic T-cell lines. Activation of the T-cell lines with guinea pig myelin basic protein (GP-BP) presented by accessory cells (APC) resulted in an increase in the number of blast cells in culture and was reflected by increased uptake of [3H]thymidine [( 3H]Tdy). The number of blasts recovered and [3H]Tdy uptake during activation was reduced drastically in the presence of OX-6, but to a much lesser extent in the presence of OX-17. OX-6 but not OX-17 appeared to block T-cell activation primarily by inhibiting APC function, since preincubation of APC but not T cells with OX-6 before stimulation resulted in complete inhibition of the cultures. After activation, the BP-1 T-cell line or D-9 clone transferred severe paralysis to normal recipient rats. Recipients of OX-6-treated BP-1 or D-9 T cells exhibited very mild or no signs, whereas recipients of OX-17-treated cells developed only slightly less severe experimental autoimmune encephalomyelitis (EAE) than recipients of untreated encephalitogenic control cultures. In contrast, treatment with OX-17 but not OX-6 reduced the ability of BP-reactive T cells to transfer delayed-type hypersensitivity reactions. Dermal testing with GP-BP in the ears of recipient rats just prior to onset of clinical signs decreased significantly the clinical intensity of EAE induced by activated BP-reactive T cells, but increased the clinical scores in rats which received unstimulated or OX-6-treated T cells. This potentiating effect of GP-BP was due most likely to the presentation of processed antigen to circulating BP-reactive T cells by APC in the ear. These results suggest that both the I-A and I-E gene products may contribute to the activation and subsequent function of encephalitogenic T cells, perhaps through separate mechanisms.