Abstract
Abstract B cells activated by nucleic-acid sensing Toll-like receptor 7 and TLR9 proliferate and secrete immune globulin. Memory B cells are more responsive due to higher TLR expression levels, but further selectivity remains largely unknown. In this study, human B cells stimulated by TLR ligands, with or without IFNα, or by T cell mimic CD40L plus IL-21 were examined to identify differentially responsive subsets, defined phenotypically or through BCR characteristics. Both stimuli induced CD27hiCD38hi plasmablasts, with TLRs inducing more IgM+ plasmablasts and IgM+ CD27hiCD38lo pre-plasmablasts than CD40L/IL-21. TLR stimulation also increased the relative proportion of IgM+ memory B cells and fostered higher IgM secretion, while CD40L/IL-21 expanded IgM- memory cells and fostered higher IgG secretion. Ig heavy chain deep sequencing showed V and J preference among TLR responsive cells, clustering TLR stimulated conditions apart from CD40L/IL-21 and control conditions. TLR stimulation expanded BCRs containing V3 at the expense of V1, and particularly expanded V3 to J4 rearrangements. More somatically hypermutated sequences were seen following TLR stimulation as compared to CD40L/IL-21. Additionally, complementarity determining region 3 segments from TLR activated cultures were shorter, more hydrophilic, and less negatively charged compared to CD40L/IL-21 or control CDR3s. Human B cells show selective sensitivity to TLR stimulation, with distinctive proliferative and genetic signatures.
Published Version
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