Asymmetric Segregation of Polarized Antigen on B Cell Division Shapes Presentation Capacity

Abstract

During the activation of humoral immune responses, B cells acquire antigen for subsequent presentation to cognate T cells. Here we show that after mouse B cells accumulate antigen, it is maintained in a polarized distribution for extended periods in vivo. Using high-throughput imaging flow cytometry, we observed that this polarization is preserved during B cell division, promoting asymmetric antigen segregation among progeny. Antigen inheritance correlates with the ability of progeny to activate T cells: Daughter cells receiving larger antigen stores exhibit a prolonged capacity to present antigen, which renders them more effective in competing for T cell help. The generation of progeny with differential capacities for antigen presentation may have implications for somatic hypermutation and class switching during affinity maturation and as B cells commit to effector cell fates.

Regulation of asymmetric cell division and polarity by Scribble is not required for humoral immunity

“…Polarized sources of stimulation and T cell help have been implicated in the induction of ACD in B cells 2,25 . Therefore, to mimic this scenario, we established a polarized source of CD40 stimulation by coating 4.5 mM beads with aCD40 antibody.…”

“…In light of the fact we saw no discernible impact on the response of Scribbledeficient mice to influenza infection, we decided to assess the extent of ACD in wild-type influenza responsive transgenic CD8 þ T cells. To rapidly assess statistically relevant numbers we used an imaging flow cytometry-based (IFC) approach that has been validated for assessing ACD in lymphocytes 25,32 . This technique provides conventional flow cytometry (CFC) data with multispectral bright-field and fluorescent images, enabling assessment of ACD of all cells undergoing mitosis, and exclusion of doublet cells through strict non-biased selection, in combination with analysis of division history.…”

“…These results are consistent with our in vivo analysis of immune responses in polarity deficient and a previous study using the same method, in which dividing B cells displaying asymmetric antigen localization showed equal, or symmetric, distribution of the polarity protein, PKC-z (ref. 25).…”

Overcoming the Dichotomy of Quantity and Quality in Antibody Responses

“…TFH always polarize to the B cell with the highest amount of collected Ag, and B cells have to get an above-threshold amount of survival signals within a limited time (6). B cells surviving this interaction with TFH all acquire the dark zone phenotype and return to the dark zone for division where they divide the previously collected Ag asymmetrically onto the daughters (17,18). B cells that kept the Ag leave the GC reaction as GC output, whereas all other B cells re-enter another round of division, mutation, and selection.…”

“…The interaction between TFHs and B cells is believed to be involved in Ig class switching (12), as well as in fate decision, that is, either recycling to another round of division and mutation (13,14) or final differentiation to either memory B cells or Ab-forming plasma cells (15,16). Alternatively, final differentiation versus recycling might be also decided by asymmetric division of the collected Ag onto the daughters of dividing B cells (17,18). According to this hypothesis, Ag-carrying B cells would preferentially differentiate to the output phenotype, whereas Ag-free B cells would stay in the GC for another round of selection.…”