Host colonization with cutaneous commensal induces humoral immunity via formation of dermal tertiary lymphoid organs

Abstract The skin is one of the largest barrier sites which harbors a plethora microorganisms. Whether microbiota promotes humoral responses remains unknown. Here we show that colonization with common commensal Staphylococcus epidermidis profoundly modulates cutaneous immunity results in serum responsiveness antigen-specific IgG antibodies. Such response uncoupled from inflammatory signals and associated induction dermal tertiary lymphoid organs closely resemble classical germinal centers. Of note, such occur tissue autonomous manner as evidenced by preserved antibody repertoire mice deficient professional organs. Our data also uncover non-redundant role for Langerhan’s cells generation specific Further, our work proposes model antigens are collected hair follicle leading to T follicular helper further expand local B cell pool an IL-21-dependent manner. We found induced antibodies can protect host against subsequent infection same microbe demonstrating importance this line defense maintaining protection. Collectively, observations highlight potential organizational flexibility first time demonstrate represent indispensable compartment actively maintains immunity.