Cbl Ubiquitin Ligases Control B Cell Exit from the Germinal-Center Reaction

Publication date: 20 March 2018
Source:Immunity, Volume 48, Issue 3
Author(s): Xin Li, Adeline Gadzinsky, Liying Gong, Haijun Tong, Virginie Calderon, Yue Li, Daisuke Kitamura, Ulf Klein, Wallace Y. Langdon, Fajian Hou, Yong-Rui Zou, Hua Gu
Selective expansion of high-affinity antigen-specific B cells in germinal centers (GCs) is a key event in antibody affinity maturation. GC B cells with improved affinity can either continue affinity-driven selection or exit the GC to differentiate into plasma cells (PCs) or memory B cells. Here we found that deleting E3 ubiquitin ligases Cbl and Cbl-b (Cbls) in GC B cells resulted in the early exit of high-affinity antigen-specific B cells from the GC reaction and thus impaired clonal expansion. Cbls were highly expressed in GC light zone (LZ) B cells, where they promoted the ubiquitination and degradation of Irf4, a transcription factor facilitating PC fate choice. Strong CD40 and BCR stimulation triggered the Cbl degradation, resulting in increased Irf4 expression and exit from GC affinity selection. Thus, a regulatory cascade that is centered on the Cbl ubiquitin ligases ensures affinity-driven clonal expansion by connecting BCR affinity signals with differentiation programs.

Graphical abstract

Teaser

Li et al. find that clonal expansion of high affinity B cells in GCs depends on the Cbl ubiquitin ligases, which prevent premature GC exit by promoting the degradation of Irf4 in light zone B cells. Strong CD40 and BCR signals trigger Cbl degradation, thus enabling GC exit.


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