Long-lived IgM plasma cells confer host protection against viral challenge (LYM6P.717)

Abstract Long-lived plasma cells are critical to immune memory, as they continuously secrete antigen-specific antibodies for up to a lifetime. Antigen-stimulated B cells, with T cell help, undergo affinity maturation within germinal centers and home to the bone marrow microenvironment where they persist as long-lived IgG plasma cells. Here we show that antigen-specific IgM plasma cells can also persist in the spleen for a lifetime. These IgM plasma cells can develop independent of the germinal center. Interestingly, despite being germinal center-independent, these cells exhibited somatic mutations in their expressed IgV heavy chain loci. Finally, we present data that antibodies from these IgM plasma cells can confer protective immunity to the host.