Blood-borne human plasma cells in steady state are derived from mucosal immune responses
Providing humoral immunity, antibody-secreting plasma cells and their immediate precursors, the plasmablasts, are generated in systemic and mucosal immune reactions. Despite their key role in maintaining immunity and immunopathology, little is known about their homeostasis. Here we show that plasmablasts and plasma cells are always detectable in human blood at low frequency in any unimmunized dono