FLICE-inhibitory Protein is a Key Regulator of Germinal Center B Cell Apoptosis
Overview
General Medicine
Authors
Affiliations
Affinity maturation of the B cell response to antigen (Ag) takes place in the germinal centers (GCs) of secondary follicles. Two sequential molecular mechanisms underpin this process. First, the B cell repertoire is diversified through hypermutation of the immunoglobulin (Ig) variable region genes. Second, mutant B cell clones with improved affinity for Ag are positively selected by Ag and CD40 ligand (L). This selection step is contingent upon "priming" of GC B cells for apoptosis. The molecular means by which B cell apoptosis is initiated and controlled in the GC remains unclear. Here, we show that GC B cell apoptosis is preceded by the rapid activation of caspase-8 at the level of CD95 death-inducing signaling complex (DISC). We found that GC B cells ex vivo display a preformed inactive DISC containing Fas-associated death domain-containing protein (FADD), procaspase-8, and the long isoform of cellular FADD-like IL-1beta-converting enzyme-inhibitory protein (c-FLIP(L)) but not the CD95L. In culture, c-FLIP(L) is rapidly lost from the CD95 DISC unless GC B cells are exposed to the survival signal provided by CD40L. Our results suggest that (a) the death receptor signaling pathway is involved in the affinity maturation of antibodies, and (b) c-FLIP(L) plays an active role in positive selection of B cells in the GC.
Guegan J, Pollet J, Ginestier C, Charafe-Jauffret E, Peter M, Legembre P iScience. 2021; 24(12):103538.
PMID: 34917906 PMC: 8666665. DOI: 10.1016/j.isci.2021.103538.
CRISPR/Cas9 Screens Reveal Multiple Layers of B cell CD40 Regulation.
Jiang C, Trudeau S, Cheong T, Guo R, Teng M, Wang L Cell Rep. 2019; 28(5):1307-1322.e8.
PMID: 31365872 PMC: 6684324. DOI: 10.1016/j.celrep.2019.06.079.
Mucosal T follicular helper cells in SIV-infected rhesus macaques: contributing role of IL-27.
Moukambi F, Rabezanahary H, Fortier Y, Rodrigues V, Clain J, Benmadid-Laktout G Mucosal Immunol. 2019; 12(4):1038-1054.
PMID: 31114010 PMC: 7746526. DOI: 10.1038/s41385-019-0174-0.
Germinal center B cell initiation, GC maturation, and the coevolution of its stromal cell niches.
Haberman A, Gonzalez D, Wong P, Zhang T, Kerfoot S Immunol Rev. 2019; 288(1):10-27.
PMID: 30874342 PMC: 10234181. DOI: 10.1111/imr.12731.
Smulski C, Decossas M, Chekkat N, Beyrath J, Willen L, Guichard G Cell Death Dis. 2017; 8(2):e2601.
PMID: 28182009 PMC: 5386471. DOI: 10.1038/cddis.2017.22.