Memory B cells with extraordinary longevity upon smallpox vaccination: Implications for type 1 hypersensitivities

Abstract

The immunological memory allows fast responding to pathogens that previously invaded the immune system. One of the key players are memory B cells (MBC). MBCs are generated upon crosstalk with antigen-specific T cells. They, subsequently, enter the light zone of the germinal center where they undergo somatic hypermutations. Upon migrating to the dark zone, high affinity clones are selected by their ability to interact with follicular dendritic and T cells. Selected clones can differentiate into MBCs residing in the spleen or peripheral blood (Figure 1). 1 To gain a better understanding of MBCs, Chappert and colleagues isolated B5 (smallpox antigen)-specific IgG + B cells from the spleen of deceased donors who received a smallpox vaccination during their lifetime. This study offered the unique opportunity to elucidate the longevity of MBCs as smallpox was eradicated more than 40 years ago, ensuring no re-occurring exposure since 1980. Isolated B5 + MBCs showed an IgG + , CD21 + , CD27 + , CD73 + phenotype, but no distinct (surface) markers were identified to distinguish B5 + MBCs from the regular MBC population. 2 Moreover, B5 + MBCs