[HTML][HTML] Control of the B cell-intrinsic tolerance programs by ubiquitin ligases Cbl and Cbl-b

Y Kitaura, IK Jang, Y Wang, YC Han, T Inazu… - Immunity, 2007 - cell.com
Y Kitaura, IK Jang, Y Wang, YC Han, T Inazu, EJ Cadera, M Schlissel, RR Hardy, H Gu
Immunity, 2007cell.com
B cell receptor (BCR) signaling plays a critical role in B cell tolerance and activation. Here,
we show that mice with B cell-specific ablation of both Cbl and Cbl-b (Cbl−/− Cblb−/−)
manifested systemic lupus erythematosus (SLE)-like autoimmune disease. The Cbl double
deficiency resulted in a substantial increase in marginal zone (MZ) and B1 B cells. The
mutant B cells were not hyperresponsive in terms of proliferation and antibody production
upon BCR stimulation; however, B cell anergy to protein antigen appeared to be impaired …
Summary
B cell receptor (BCR) signaling plays a critical role in B cell tolerance and activation. Here, we show that mice with B cell-specific ablation of both Cbl and Cbl-b (Cbl−/−Cblb−/−) manifested systemic lupus erythematosus (SLE)-like autoimmune disease. The Cbl double deficiency resulted in a substantial increase in marginal zone (MZ) and B1 B cells. The mutant B cells were not hyperresponsive in terms of proliferation and antibody production upon BCR stimulation; however, B cell anergy to protein antigen appeared to be impaired. Concomitantly, BCR-proximal signaling, including tyrosine phosphorylation of Syk tyrosine kinase, Phospholipase C-γ2 (PLC-γ2), and Rho-family GTP-GDP exchange factor Vav, and Ca2+ mobilization were enhanced, whereas tyrosine phosphorylation of adaptor protein BLNK was substantially attenuated in the mutant B cells. These results suggested that the loss of coordination between these pathways was responsible for the impaired B cell tolerance induction. Thus, Cbl proteins control B cell-intrinsic checkpoint of immune tolerance, possibly through coordinating multiple BCR-proximal signaling pathways during anergy induction.
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