αv Integrins regulate germinal center B cell responses through noncanonical autophagy
Fiona Raso, … , Adam Lacy-Hulbert, Mridu Acharya
Fiona Raso, … , Adam Lacy-Hulbert, Mridu Acharya
Published July 12, 2018
Citation Information: J Clin Invest. 2018;128(9):4163-4178. https://doi.org/10.1172/JCI99597.
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Research Article Immunology

αv Integrins regulate germinal center B cell responses through noncanonical autophagy

Abstract

Germinal centers (GCs) are major sites of clonal B cell expansion and generation of long-lived, high-affinity antibody responses to pathogens. Signaling through TLRs on B cells promotes many aspects of GC B cell responses, including affinity maturation, class switching, and differentiation into long-lived memory and plasma cells. A major challenge for effective vaccination is identifying strategies to specifically promote GC B cell responses. Here, we have identified a mechanism of regulation of GC B cell TLR signaling, mediated by αv integrins and noncanonical autophagy. Using B cell–specific αv-KO mice, we show that loss of αv-mediated TLR regulation increased GC B cell expansion, somatic hypermutation, class switching, and generation of long-lived plasma cells after immunization with virus-like particles (VLPs) or antigens associated with TLR ligand adjuvants. Furthermore, targeting αv-mediated regulation increased the magnitude and breadth of antibody responses to influenza virus vaccination. These data therefore identify a mechanism of regulation of GC B cells that can be targeted to enhance antibody responses to vaccination.

Authors

Fiona Raso, Sara Sagadiev, Samuel Du, Emily Gage, Tanvi Arkatkar, Genita Metzler, Lynda M. Stuart, Mark T. Orr, David J. Rawlings, Shaun W. Jackson, Adam Lacy-Hulbert, Mridu Acharya

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Figure 1

Increased GC B cells in αv-CD19 mice.

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Increased GC B cells in αv-CD19 mice. (A) Histograms show staining for α...
(A) Histograms show staining for αv on CD19+ cells from control mice (solid lines) or αv-CD19 mice (dotted lines). (B) Western blot analysis of NF-κB p65 in nuclear fractions from FACS-sorted PP GC cells from control and αv-CD19 mice stimulated in vitro with CpG for the indicated times (minutes). Also shown is the staining for LSD1 to confirm equal loading of nuclear protein. (C) Confocal microscopy of FACS-sorted PP GC B cells from control and αv-CD19 mice with or without in vitro stimulation with 2 μM CpG DNA for 2 hours. Cells are stained for LC3b (red) or nuclear DNA (Hoescht, white). Images show representative examples of distributed LC3 expression (unstimulated control and αv-CD19) and punctate expression (CpG-treated control). Scale bar: 2.5 μm. (D) Proportions of cells undergoing LC3 reorganization, based on counting of at least 30 cells/condition. P values are shown (Pearson’s χ2 test). (E) Representative FACS plots of cells from PP of control and αv-CD19 mice gated on CD19+ B cells and stained with FAS/GL7. Gates used for identification of GC B cells and frequency of GC B cells are shown. (F) Quantification of frequency of GC B cells in mesenteric lymph nodes (MLN), PP, and colon lamina propria in control and αv-CD19 mice. GC B cells were gated as CD19+GL7+FAS+ cells as in E. Each point represents an individual mouse, and at least 5 mice were analyzed for each group. P values of less than 0.05 are shown (2- tailed Student’s t test). For all data shown, similar results were seen in at least 3 independent experiment.