Abstract
BackgroundSteroid-responsive meningitis-arteritis (SRMA) is an immune-mediated disorder characterized by neutrophilic pleocytosis and an arteritis particularly in the cervical leptomeninges. Previous studies of the disease have shown increased levels of IL-6 and TGF-ß1 in cerebrospinal fluid (CSF). In the presence of these cytokines, naive CD4+ cells differentiate into Th17 lymphocytes which synthesize interleukin 17 (IL-17). It has been shown that IL-17 plays an active role in autoimmune diseases, it induces and mediates inflammatory responses and has an important role in recruitment of neutrophils. The hypothesis of a Th17-skewed immune response in SRMA should be supported by evaluating IL-17 and CD40L, inducing the vasculitis.MethodsAn enzyme-linked immunosorbent assay (ELISA) was performed to measure IL-17 and CD40L in serum and CSF from a total of 79 dogs. Measurements of patients suffering from SRMA in the acute state (SRMA A) were compared with levels of patients under treatment with steroids (SRMA T), recurrence of the disease (SRMA R), other neurological disorders, and healthy dogs, using the two-part test. Additionally, secretion of IL-17 and interferon gamma (IFN-γ) from the peripheral blood mononuclear cells (PBMCs) was confirmed by an enzyme-linked immunospot (ELISpot) assay.ResultsSignificant higher levels of IL-17 were found in CSF of dogs with SRMA A compared with SRMA T, other neurological disorders and healthy dogs (p < 0.0001). In addition, levels of CD40L in CSF in dogs with SRMA A and SRMA R were significantly higher than in those with SRMA T (p = 0.0004) and healthy controls (p = 0.014). Furthermore, CSF concentrations of IL-17 and CD40L showed a strong positive correlation among each other (rSpear = 0.6601; p < 0.0001) and with the degree of pleocytosis (rSpear = 0.8842; p < 0.0001 and rSpear = 0.6649; p < 0.0001, respectively). IL-17 synthesis from PBMCs in SRMA patients was confirmed; however, IL-17 is mainly intrathecally produced.ConclusionsThese results imply that Th17 cells are inducing the autoimmune response in SRMA and are involved in the severe neutrophilic pleocytosis and disruption of the blood-brain barrier (BBB). CD-40L intrathecal synthesis might be involved in the striking vasculitis. The investigation of the role of IL-17 in SRMA might elucidate important pathomechanism and open new therapeutic strategies.
Highlights
Steroid-responsive meningitis-arteritis (SRMA) is an immune-mediated disorder characterized by neutrophilic pleocytosis and an arteritis in the cervical leptomeninges
Freundt-Revilla et al Journal of Neuroinflammation (2017) 14:20 (Continued from previous page). These results imply that T helper 17 (Th17) cells are inducing the autoimmune response in SRMA and are involved in the severe neutrophilic pleocytosis and disruption of the blood-brain barrier (BBB)
Cluster of differentiation (CD)-40L intrathecal synthesis might be involved in the striking vasculitis
Summary
Steroid-responsive meningitis-arteritis (SRMA) is an immune-mediated disorder characterized by neutrophilic pleocytosis and an arteritis in the cervical leptomeninges. Steroid-responsive meningitis-arteritis (SRMA) is the most frequently diagnosed meningitis in canines [1] It is a systemic immune-mediated disorder [2] characterized by systemic inflammatory lesions of the vessels, but in the cervical leptomeninges [3, 4] and in a recognized large animal model for neutrophilic meningitis [5]. This disorder affects typically young adult dogs [6], can occur in any breed, beagles, boxers, Bernese mountain dogs [3, 7], Weimaraners, Nova Scotia duck tolling retrievers [2], and Petit Basset Griffon Vendéen [8] are over-represented. The protracted form may be observed following relapses and neurological deficits like reduced menace response, anisocoria, strabismus, and variable degrees of paresis and ataxia might occur; CSF analysis at this stage reveals mononuclear or mixed cell populations [7]
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