The cellular origins of memory B cells

Area of Science:

• Immunology
• Cell Biology

Background:

• Memory B cells and antibody-forming cell (AFC) precursors were thought to arise from similar naive B cell populations.
• Recent evidence suggests distinct precursor populations may exist for these two B cell fates.

Purpose of the Study:

• To investigate the existence and characteristics of distinct naive B cell precursor populations for memory B cells and AFCs.
• To elucidate the developmental potential and surface marker expression of these precursor subsets.

Main Methods:

• Fractionation of naive peripheral B cells based on surface heat stable antigen (HSA) expression into HSAlo and HSAint-hi populations.
• In vitro antigenic stimulation of isolated HSAlo and HSAint-hi B cell populations.
• Analysis of cellular progeny for memory B cell generation, antibody formation, somatic mutation accumulation, and germinal center formation.

Main Results:

• HSAlo B cells were enriched for memory B cell progenitors, generating memory B cell clones without antibody formation.
• HSAint-hi B cells were enriched for AFC precursors, yielding AFC responses but not memory B cells.
• Progeny of HSAlo cells exhibited somatic mutation accumulation and germinal center origination, retaining stem cell-like properties.

Conclusions:

• Two distinct naive B cell precursor populations, HSAlo and HSAint-hi, pre-exist and are committed to distinct fates.
• HSAlo cells are progenitors of memory B cells with self-renewal and mutation capabilities.
• HSAint-hi cells are terminally differentiated precursors for AFCs, resolving disparate biological characteristics.