Venous plexus-associated lymphoid hubs support meningeal humoral immunity
There is increasing interest in how immune cells in the meninges, the membranes that surround the brain and spinal cord, contribute to homeostasis and disease in the central nervous system (CNS)1,2. The outer layer of meninges, the dura mater, has recently been described to contain both innate and adaptive immune cells, and function as a site for B cell development. Here, we identified organised lymphoid structures protecting fenestrated vasculature in the dura mater that we term dural-associated lymphoid tissue (DALT). We found the most elaborate immune organization, including lymphatic vessels, surrounding the rostral_x0002_rhinal confluence of sinuses. We termed this structure that interfaced with the skull bone marrow and a comparable venous plexus at the skull base, the rostral-rhinal venolymphatic hub. Immune aggregates were present in DALT during homeostasis and expanded with age or following challenge with systemic or nasal antigens. DALT contained germinal centre (GC) B cells, and supported the generation of somatically mutated, antibody-producing cells in response to a nasal pathogen challenge. Inhibition of lymphocyte entry into the rostral-rhinal hub at the time of nasal viral challenge abrogated the generation of germinal centre B cells and class-switched plasma cells, as did perturbation of B-T cell interactions. These data demonstrate lymphoid architecture around vasculature in dura mater that can sample antigens and rapidly support humoral immune responses following local pathogen challenge. Overall design: Rostral rhinal hubs isolated from the dorsal meninges were analyzed by scRNAseq in two groups of mice (uninfected vs day 8 post-VSV infection) in two independent experiments.  Experiment#1: uninfected (Men_Naive), d8 VSV (Men_VSV); Experiment#2: uninfected (PBS_HUB), d8 VSV (VSV_HUB)