Mechanisms of neuropsychiatric lupus: The relative roles of the blood-cerebrospinal fluid barrier versus blood-brain barrier

The pathogenesis of neuropsychiatric lupus (NPSLE) is believed to include the entry of circulating neuropathic antibodies to,the brain via a pathologically permeable blood-brain barrier (BBB). Nevertheless, direct evidence of BBB pathology or mechanisms underlying BBB dysfunction is missing. Here, we examined BBB integrity in an established NPSLE mouse model (MRL/fas(1Pr)/(lP1)). Surprisingly, challenging the barrier with various exogenous tracers demonstrated insignificant changes in BBB permeability. Furthermore, electron microscopy showed no ultrastructure changes supporting hyper permeability. However, we found that abnormal function of the blood-cerebrospinal fluid barrier (BCSFB) in the choroid plexus underlies brain exposure to neuropathic antibodies. Considerable intrathecal lymphocyte infiltration likely occurs through the BCSFB, accompanied by epithelial hyper permeability to antibodies. Our results challenge the commonly held view of BBB disruption in NPSLE, supporting a shift in focus to BCSFB dysfunction as a causative factor in the disease. (C) 2018 Elsevier Ltd. All rights reserved.