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High-affinity IgM+ memory B cells are defective in differentiation into IgM antibody-secreting cells by re-stimulation with a T cell-dependent antigen.

Yasuyuki TashiroAkikazu MurakamiYasushi HaraTakeyuki ShimizuMasato KuboRyo GoitsukaHidehiro KishimotoTakachika Azuma
Published in: Scientific reports (2018)
IgM antibodies (Abs) are thought to play a major role in humoral immunity but only at the early stage of the primary immune response. However, two subsets of IgM+ memory B cells (MBCs), one with high affinity gained by means of multiple somatic hypermutation (SHM) and the other with low affinity and no SHMs, are generated through the germinal center (GC)-dependent and GC-independent (non-GC) pathway, respectively, after immunization with (4-hydroxy-3-nitrophenyl)acetyl (NP)-chicken γ-globulin. Surprisingly, an analysis of antibody-secreting cells reveals that a large amount of anti-NP IgM Ab with few SHMs is secreted during the recall response, indicating that only non-GC MBCs have terminal differentiation potential. Since secondary IgM Abs are capable of binding to dinitrophenyl ligands, they likely provide broad cross-reactivity in defense against microbial infection.
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