Wekerle (Munich, Germany). otherwise undetected concentrations, anti-MOG Ab enabled Fc-mediated APC acknowledgement CID16020046 of intact MOG; internalized, processed and offered MOG activated na?ve T cells to differentiate in an encephalitogenic manner. In a series of translational experiments, anti-MOG Ab from two patients with Rabbit Polyclonal to MRPL20 an acute flare of CNS inflammation likewise facilitated detection of human MOG. Jointly, these observations spotlight Ab-mediated opsonization of endogenous CNS auto-antigen as a novel disease- and/or relapse-triggering mechanism in CNS demyelinating disorders. Electronic supplementary material The online version of this article (doi:10.1007/s00401-016-1559-8) contains supplementary material, which is available to authorized users. Keywords: Auto-antibodies, Opsonization, Myeloid antigen-presenting cells, Fc receptor, Experimental autoimmune encephalomyelitis, Multiple sclerosis Introduction B cells, plasma cells and antibodies (Ab) are progressively recognized as important players in inflammatory central nervous system (CNS) demyelinating diseases, such as multiple sclerosis (MS), neuromyelitis optica (NMO) and related disorders. Within the cerebrospinal fluid of the majority of MS patients, locally supported plasma cells constantly produce oligoclonal immunoglobulin (Ig) [36, 51], which remain a hallmark diagnostic obtaining. B and plasma cells are commonly found in MS lesions [41] and Ab deposition co-localizes with match activation and ongoing demyelination [16]. In NMO, persuasive evidence suggests that anti-aquaporin (AQP)-4-Ab selectively target astrocytes resulting in subsequent demyelination [29]. B cells constitutively express major histocompatibility complex (MHC) class II and act as powerful antigen-presenting cells (APC) when they identify conformational protein antigen via their B cell receptor (BCR) [9]. B cells from MS patients reveal indicators of chronic activation with a differential shift toward antigen-experienced memory B cells generating pro-inflammatory cytokines, such as interleukin-6 [12] and granulocyte-macrophage colony-stimulating factor (GM-CSF) [25]. These properties, along with the fulminant success of the clinical trials screening anti-CD20 monoclonal Ab [18, 19], suggest that antigen-experienced B cells may act as potent APC in MS. A series of recent experimental investigations aimed to directly address the role of B cells, plasma cells and Ab in development of inflammatory CNS demyelinating disease. First, transgenic mice were generated in which B cells identify myelin oligodendrocyte protein (MOG) and plasma cells constitutively produce high titers of pathogenic anti-MOG Ab (Th mice); upon active immunization, these mice showed a fulminant course of experimental autoimmune encephalomyelitis (EAE) with enhanced CNS demyelination [27]. When Th mice were further crossed with MOG T cell receptor (TCR) transgenic mice (2D2 mice) [4], the producing line (Thx2D2) even spontaneously developed EAE [3, 21]. A similar observation was reported around the SJL/J background, furthermore, CID16020046 demonstrating that transgenic T cells can recruit endogenous MOG-specific B cells [39]. In an attempt to elucidate which immunological components were required for spontaneous EAE development, a pivotal recent report exhibited that myelin-recognizing B and T cells sufficed to trigger EAE development in C57BL/6 CID16020046 mice [34], corroborating that auto-reactive B cells are an essential APC population in this model. Notwithstanding these results, we here statement on a crucial complementary role of CNS-reactive Ab likely completing the scenario how initial acknowledgement of auto-antigen in development of CNS autoimmune disease can occur. We show that traces of CNS antigen are opsonized by myelin-reactive Ab, making them recognizable for Fc receptor transporting myeloid APC. Subsequent to internalization, processed myelin antigen is usually offered to myelin-recognizing T cells triggering their growth and encephalitogenic differentiation. We demonstrate that this mechanism indeed sparks experimental CNS autoimmunity; first, we show that in the absence of B cells, Thx2D2 mice develop spontaneous EAE indistinguishable from its course in mice made up of B cells. Second, and most importantly, adoptive transfer of serum from Th mice or of purified anti-MOG Ab 8.18C5 into na?ve 2D2 recipients CID16020046 triggered activation and growth of T cells followed by severe and strong EAE,.