%0 Figure %A Roders, Nathalie %A Herr, Florence %A Ambroise, Gorbatchev %A Thaunat, Olivier %A Portier, Alain %A Vazquez, Aimé %A Durrbach, Antoine %D 2018 %T image_1_SYK Inhibition Induces Apoptosis in Germinal Center-Like B Cells by Modulating the Antiapoptotic Protein Myeloid Cell Leukemia-1, Affecting B-Cell Activation and Antibody Production.tiff %U https://frontiersin.figshare.com/articles/figure/image_1_SYK_Inhibition_Induces_Apoptosis_in_Germinal_Center-Like_B_Cells_by_Modulating_the_Antiapoptotic_Protein_Myeloid_Cell_Leukemia-1_Affecting_B-Cell_Activation_and_Antibody_Production_tiff/6174686 %R 10.3389/fimmu.2018.00787.s001 %2 https://frontiersin.figshare.com/ndownloader/files/11174138 %K germinal center B-cells %K spleen tyrosine kinase inhibition %K myeloid cell leukemia-1 %K apoptosis %K antibody-mediated rejection %X

B cells play a major role in the antibody-mediated rejection (AMR) of solid organ transplants, a major public health concern. The germinal center (GC) is involved in the generation of donor-specific antibody-producing plasma cells and memory B cells, which are often poorly controlled by current treatments. Myeloid cell leukemia-1 (Mcl-1), an antiapoptotic member of the B-cell lymphoma-2 family, is essential for maintenance of the GC reaction and B-cell differentiation. During chronic AMR (cAMR), tertiary lymphoid structures resembling GCs appear in the rejected organ, suggesting local lymphoid neogenesis. We report the infiltration of the kidneys with B cells expressing Mcl-1 in patients with cAMR. We modulated GC viability by impairing B-cell receptor signaling, by spleen tyrosine kinase (SYK) inhibition. SYK inhibition lowers viability and Mcl-1 protein levels in Burkitt’s lymphoma cell lines. This downregulation of Mcl-1 is coordinated at the transcriptional level, possibly by signal transducer and activator of transcription 3 (STAT3), as shown by (1) the impaired translocation of STAT3 to the nucleus following SYK inhibition, and (2) the lower levels of Mcl-1 transcription upon STAT3 inhibition. Mcl-1 overproduction prevented cells from entering apoptosis following SYK inhibition. In vitro studies with primary tonsillar B cells confirmed that SYK inhibition impaired cell survival and decreased Mcl-1 protein levels. It also impaired B-cell activation and immunoglobulin G secretion by tonsillar B cells. These findings suggest that the SYK–Mcl-1 pathway could be targeted, to improve graft survival by manipulating the humoral immune response.

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