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. 2022 Jul 25;13:958392. doi: 10.3389/fimmu.2022.958392

Figure 2.

Figure 2

Anaphylatoxin receptor activation on TFH cells and GC B cells controls the production of IgG (auto)antibodies (A) C5aR1 signaling on CD4+ T cells facilitates the expansion of TFH cells and their subsequent production of IL-4 and IL-21, which are crucial for the germinal center reaction. The absence of C5aR1 signaling leads to an attenuated TFH cell expansion and reduced GC reaction. (B) During the GC reaction, C3a and C5a engage their receptors, C3aR and C5aR1 respectively, on GC B cells, driving B cell proliferation and differentiation into memory B cells (Bmem) as well as long-lived plasma cells (PC). When complement activation is inhibited (bottom) either by decay-accelerating factor (DAF, CD55) over-expression or deletion of C3aR/C5aR1 on GC B cells, (1) GCs collapse prematurely due to impaired dark zone re-entry and affinity maturation (2), resulting in decreased generation of Bmem and long-lived PCs (3). Created in BioRender.com.