B cell–derived IL-4 acts on podocytes to induce proteinuria and foot process effacement
Alfred H.J. Kim, Jun-Jae Chung, Shreeram Akilesh, Ania Koziell, Sanjay Jain, Jeffrey B. Hodgin, Mark J. Miller, Thaddeus S. Stappenbeck, Jeffrey H. Miner, Andrey S. Shaw
Alfred H.J. Kim, Jun-Jae Chung, Shreeram Akilesh, Ania Koziell, Sanjay Jain, Jeffrey B. Hodgin, Mark J. Miller, Thaddeus S. Stappenbeck, Jeffrey H. Miner, Andrey S. Shaw
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Research Article Immunology Nephrology

B cell–derived IL-4 acts on podocytes to induce proteinuria and foot process effacement

Abstract

The efficacy of B cell depletion therapies in diseases such as nephrotic syndrome and rheumatoid arthritis suggests a broader role in B cells in human disease than previously recognized. In some of these diseases, such as the minimal change disease subtype of nephrotic syndrome, pathogenic antibodies and immune complexes are not involved. We hypothesized that B cells, activated in the kidney, might produce cytokines capable of directly inducing cell injury and proteinuria. To directly test our hypothesis, we targeted a model antigen to the kidney glomerulus and showed that transfer of antigen-specific B cells could induce glomerular injury and proteinuria. This effect was mediated by IL-4, as transfer of IL-4–deficient B cells did not induce proteinuria. Overexpression of IL-4 in mice was sufficient to induce kidney injury and proteinuria and could be attenuated by JAK kinase inhibitors. Since IL-4 is a specific activator of STAT6, we analyzed kidney biopsies and demonstrated STAT6 activation in up to 1 of 3 of minimal change disease patients, suggesting IL-4 or IL-13 exposure in these patients. These data suggest that the role of B cells in nephrotic syndrome could be mediated by cytokines.

Authors

Alfred H.J. Kim, Jun-Jae Chung, Shreeram Akilesh, Ania Koziell, Sanjay Jain, Jeffrey B. Hodgin, Mark J. Miller, Thaddeus S. Stappenbeck, Jeffrey H. Miner, Andrey S. Shaw

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Figure 2

IL-4 induces podocyte membrane ruffling and widespread foot process retraction.

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IL-4 induces podocyte membrane ruffling and widespread foot process retr...
(A) Differential interference contrast live-cell imaging was used to obtain kymographs from individual differentiated cultured murine podocytes. Each cell was imaged individually from separate podocyte cultures. Representative kymographs (time = 20 minutes) before (left column) and after (right column) the addition of IL-4 (10 ng/ml, top row) or IL-4 with anti–IL-4 antibody (5 μg/ml, bottom row) are shown. IL-4 caused pronounced membrane ruffling that was abrogated by anti–IL-4 treatment (also see Supplemental Videos 1 and 2). Original magnification, ×~1,100. (B) Kymograph analysis was used to quantitate actin spike lengths (ruffling index) of 5 locations per cultured podocyte for the cytokines tested (IL-13: 10 ng/ml, IFN-γ: 100 ng/ml, TNF-α: 10 ng/ml). IL-4 and IL-13 have enhanced membrane ruffling dynamics. IL-4 promoted an equivalent level of ruffling as a known activator of Rac, EGF (20 ng/ml), which was reversed with anti–IL-4 antibody. Each symbol represents the average relative cell membrane displacement over time at 5 regions of a single cell. Each cell mean ± SD of 3 experiments, with 3–4 cells/experiment (total of 10 cells analyzed/group). (C) Representative scanning electron microscopy images of glomeruli from minced renal cortices incubated ex vivo for 20 minutes with IL-4 (10 ng/ml), IL-4 with anti–IL-4 antibody (5 μg/ml), TNF-α (10 ng/ml), or positive control EGF (20 ng/ml). IL-4 treatment induced massive foot process retractions similar to that induced by EGF. TNF-α and IL-4 plus anti–IL-4 did not alter foot process morphology, consistent with the membrane ruffling data. Scale bar: 20 μm. *P < 0.001, **P < 0.005, ***P < 0.004, ****P < 0.03 by 1-way ANOVA with Bonferroni correction.