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latter group used a different immunization protocol that included a single administration of 200 μg of MOG and two injections of 400 ng of pertussis toxin (48 h apart). In the present report, we confirm that NG2-deficient mice develop milder EAE clinical score compared to control mice (Fig. 1a, b), similar to what was observed by Ferrara et al. We utilized an NG2-EYFP knock-in reporter mouse line we have previously generated, where homozygous EYFP integration into the NG2 locus yields NG2-deficient mice (NG2) [7]. Twenty-five days after immunization, the extent of demyelination in spinal cords of NG2deficient mice was negligible in comparison to control animals (Fig. 1c, e). In addition, infiltrating immune cells were scarcely present in the CNS of NG2-deficient mice at this time point of disease progression (Fig. 1d, f). It should be noted that our immunization protocol differed from those applied in aforementioned studies, consisting of a single injection of MOG35–55 (50 μg)/CFA and two injections of 200 ng of pertussis toxin administered on the day and 2 days after immunization. Importantly, application of another lot of pertussis toxin, with different activity values, resulted in the development of disease in NG2 mice, although the severity was still milder in comparison to controls (Supplemental Fig. 1). The mechanism of pertussis toxin action in EAE is not completely understood, but some of the proposed functions include modulation of the blood–brain barrier permeability and promotion of pathogenic T helper 17 (Th17) cell development and expansion [3, 10]. Therefore, it is likely that after a stronger boost of the immune system, such as varying concentrations of MOG, CFA and/or pertussis toxin, the threshold for the disease onset can be reached also in NG2-deficient mice. However, the proportion of Th1 and Th17 cell subsets was similar between knockout and control mice, based on the expression of signature cytokines (Supplemental Fig. 2). Nerve/glial antigen 2 (NG2) is a large transmembrane chondroitin sulphate proteoglycan expressed mainly by oligodendrocyte precursor cells in the developing and adult central nervous system (CNS) and pericytes in various organs throughout the body [14]. Numerous studies reported increased levels of this molecule after CNS injury, but its relevance remained questionable [5, 6, 9, 11]. In recent years, contradicting studies have been published concerning the role of NG2 molecule in experimental autoimmune encephalomyelitis (EAE). Using an immunization protocol consisting of two 100 μg doses of MOG35–55, emulsified in CFA, on days 0 and 7 and two injections of 300 ng of pertussis toxin on days 0 and 2 postimmunization, Moransard et al. demonstrated that NG2 is dispensable for EAE development [11]. In contrast, Ferrara et al. reported recently that mice of the same NG2-deficient line displayed milder EAE clinical score [4]. Of note, the