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. 2018 Sep 19;9:2011. doi: 10.3389/fimmu.2018.02011

Figure 6.

Figure 6

Mechanistic hypothesis: Lattice formation by SpA in complex with soluble IgG targets membrane-associated BCR to determine B cell fate. (A) In the presence of IgG capable of only very weak/undetectable Fc-mediated SpA binding (i.e., IgG1), the low effective valency of complexes does not result in depletion of VHIII Fab -BCR bearing B cells. (B) In the presence of IgG capable of medium level Fc-mediated SpA binding (i.e., IgG3), the greater effective valency of complexes causes cross-link VHIII BCR, resulting in a modest level of apoptotic depletion of VHIII-BCR bearing B cells. (C) In the presence of IgG capable of strong Fc-mediated SpA binding (i.e., IgG2a), B cell membrane-associated lattices are formed that cause high-level depletion of VHIII-BCR bearing B cells at 72 h after in vivo challenge, when second signal is insufficient. Red indicates a VHIII Fab-binding interaction with SpA, while blue indicates an Fc-mediated binding interaction with SpA.