Experimental allergic encephalomyelitis. Early T cells and TG cells are separate subpopulations

Experimental allergic encephalomyelitis in guinea pig: variability of response to intradermal emulsion injection

Different forms of experimental allergic encephalomyelitis were obtained in 4 groups of guinea pigs: 7 adult Hartley guinea pigs (Group I), 12 adults of the same strain (Group II), 6 juvenile strain 2 guinea pigs (Group III) and 6 juvenile strain 13 animals (Group IV), by the injection of emulsions. Groups I and II received emulsions containing 250 mg and 500 mg respectively of fresh isologous spinal cord tissue, complete Freund adjuvant (CFA) and saline solution while Groups III and IV received an emulsion containing 120 mg of isologous spinal cord, CFA, saline solution and 15 mg of Mycobacterium tuberculosis. The increased antigen load induced a disease with delayed onset and prolonged progressive course (C-P-EAE) in Groups I and II, although 8 animals showed no symptoms of illness. The findings in C-P-EAE were large demyelinated plaques, perivenous fibrosis and large areas of infiltration. Demyelinated areas occurred within the spinal cord white matter only in two asymptomatic animals. C-P-EAE was obtained in 4 of the Strain 2 animals. In conclusion, the increased antigen load induced a range of lesions in Hartley guinea pigs, although not all animals were affected. C-P-EAE was induced also in strains of guinea pig other than the Heartley strain. These different reactions may have been the outcome of partial or complete inactivation of the cell-mediated response to the inoculated antigens.

Chronic experimental allergic neuritis (EAN) in juvenile guinea pigs: immunological comparison with acute EAN in adult guinea pigs

In order to approach the mechanism of chronic or relapsing course in human chronic inflammatory demyelinating polyradiculoneuropathy, we established a chronic model of experimental allergic neuritis (EAN) in juvenile guinea pigs, and investigated the underlying cellular immune phenomenon in comparison with acute EAN in adult animals of the same strain. Two-week-old Hartley guinea pigs, sensitized with bovine peripheral nerve homogenate, developed chronic or relapsing EAN, whereas all adult animals developed acute monophasic EAN. Morphological examination of both the chronic and acute forms revealed scattered demyelination and mononuclear cell infiltrates which were essentially restricted to the peripheral nervous system, and indistinguishable from each other. Both the in vitro lymphocyte mitogenic response and in vivo skin testing revealed a significantly lower response to neuritogenic antigens (P2 protein and peripheral nerve myelin) in juvenile chronic EAN than in adult acute EAN throughout their respective courses. In addition, we showed, by means of assessing peripheral blood lymphocyte number and its subpopulations, that normal 2-week-old Hartley guinea pigs have not fully developed immunologically. These observations suggested that there was some immunological incompetence especially in cellular immunity in 2-week-old juvenile guinea pigs and that this might be one possible factor leading to chronic EAN.

Acute experimental autoimmune encephalomyelitis. Differences between T cell subsets in the blood and meningeal infiltrates in susceptible and resistant strains of guinea pigs

The percentages of early (active, high affinity-rosetting), late (total) T cells and TG cells (suppressor T cells) were determined longitudinally in the blood and meningeal infiltrating cells of Strain 13 (susceptibility) and Strain 2 (resistant) animals inoculated for acute EAE and in guinea pigs of both strains in which the disease was suppressed with myelin basic protein (MBP) in incomplete Freund's adjuvant (IFA). Reactivity of T cells to MBP and oligodendrocyte protein was tested using the antigen-reactive T cell test. After inoculation for acute EAE, a transient increase in circulating early T cells was found during the latent period in Strain 13 guinea pigs only, while both strains showed a decrease in early T cells later on. Low values of circulating TG cells were more apparent in Strain 13 than Strain 2. In infiltrating cells of the meninges, early T cell values were significantly higher in the meninges than in the blood (P less than 0.01) in Strain 13, but were only slightly elevated in Strain 2 animals. TG cell levels in meningeal infiltrates were slightly higher than corresponding blood levels in both strains. In animals which were given a suppressive regimen of MBP/IFA, circulating early T cells rose initially and showed normal values later on in both strains of guinea pigs. TG cell levels were slightly more increased in strain 13 than strain 2. In comparison to blood values, early T cells were higher in the CNS in Strain 13, and lower in the CNS in Strain 2. TG cell levels were increased over blood values in both strains. These quantitative discrepancies in T cell subset between Strain 13 and Strain 2 guinea pigs which had been inoculated for EAE might reflect a difference in the cell-mediated immune response to white matter antigens which might be related to the variation in susceptibility to EAE.