Strain specificities in cellular and molecular immunopathogenic mechanisms underlying development of experimental autoimmune encephalomyelitis in aged rats

Abstract

To understand strain-specificities of immune system in aged rats and their immunopathological implications, CD4+T lymphocyte-mediated neuroinflammation in experimental autoimmune encephalomyelitis (EAE) was studied in two strains. Upon immunization for EAE, 22-24-month-old Albino Oxford (AO) rats developed milder neurological deficit of prolonged duration compared with their Dark Agouti (DA) counterparts. Consistently, they exhibited: (i) diminished neuroantigen-specific CD4+T lymphocyte generation in draining lymph nodes (reflecting lower density of high-affinity IL-2 receptor complex on their surface and higher CD4+FoxP3+CD25+regulatory cell frequency); (ii) less favorable spinal cord expression of CXCL12 and CCL2, and consequently diminished infiltration of neuroantigen-specific CD4+T lymphocytes, including highly pathogenic IL-17+IFN-gamma+ones, and inflammatory monocytes into the spinal cord and (iii) subsequently impaired CD4+T lymphocyte reactivation/survival and differentiation into highly pathogenic IL-17+cells (reflecting downregulated expression of IL-1 beta, IL-6 and IL-23/p19). On the other hand, when the neurological deficit reached maximum/plateau, in AO rat spinal cord was found lower CD4+FoxP3+CD25+ cell frequency followed by higher frequency of IL-10-producing CD8+T cells, which most likely also belong to regulatory T lymphocytes. Thus, the altered relation between regulatory T cell and effector CD4+T cell subsets was linked with persistence of mild neuroinflammation in AO rat EAE model. (C) 2017 Elsevier B.V. All rights reserved.