Humoral immune defense of the central nervous system

Infiltration of the central nervous system (CNS) parenchyma by peripheral B cells provides an important defense against neurotropic infections but also contributes to different neuroinflammatory diseases. While the periphery is known to support CNS humoral immune responses, recent studies have demonstrated that the meninges receive a steady influx of B cells from the skull bone marrow and provide an important niche for B-cell development and tolerance. Meningeal vascular barriers like the dural venous sinuses are also inhabited by plasma cells that secrete antibodies locally and sequester pathogens, preventing their entry into the CNS. However, these beneficial aspects of CNS humoral immunity are sometimes offset by pathological responses such as the development of meningeal ectopic lymphoid structures that promote autoimmune damage in the underlying parenchyma. In this review, we discuss recent advances in our understanding of CNS humoral immunity, with an emphasis on anatomy, infections, and autoimmune disease.