Molecular characterization of influenza-specific memory B cell subsets residing in human tissues

Abstract

Abstract B cells can be divided into distinct subsets based on origin, activation history and functional attributes. Most human studies, which have characterized bulk polyclonal populations of circulating B cells, suggest heterogeneity between the different B cell subsets. Indeed, we showed that memory B (Bmem) and plasma cells from the blood of the same donor exhibit distinct patterns of isotype distribution, mutational burden and have relatively limited clonal sharing. However, this heterogeneity may not extend to comparisons between the same B cell subset found within different tissues or cells that share the same reactivity. To test this, we examined influenza hemagglutinin (HA)-specific Bmem in multiple donor-matched tissues. We first generated a high-throughput bead array displaying HAs from the seasonal (H1, H3) and pandemic (H2, H5, H7, H9) flu strains and screened the serum from >80 brain-dead human tissue donors. All the donors exhibited high serum IgG reactivity against the circulating strains. We also identified serum reactivity in some donors for HAs that are not circulating in humans, suggesting that these donors likely have HA-specific IgG that are potentially broadly reactive and may have cross-reactive B cells. To directly identify B cells with cross-reactive potential, we enumerated H1 (CA09) and H2 (NETH1999) specific Bmem by flow cytometry. We show that Bmem specific for H1 or H2 are found in the spleen and blood whereas Bmem specific for both H1 and H2 are present in the mediastinal lymph node (LN), spleen and mesenteric LN. The data suggest that the repertoire of HA specific Bmem likely differ between tissues. Going forward, we will characterize the repertoire and molecular signatures of these HA-specific Bmem populations. Supported by grants from NIH (U19 AI142737,)