Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Sep 22;23(19):11132.
doi: 10.3390/ijms231911132.

Fcα Receptor-1-Activated Monocytes Promote B Lymphocyte Migration and IgA Isotype Switching

Amélie V Bos  1   2 , Melissa M J van Gool  1   2 , Annelot C Breedveld  1   2 , Richard van der Mast  1   2 , Casper Marsman  3 , Gerd Bouma  4 , Mark A van de Wiel  5   6 , S Marieke van Ham  3   7 , Reina E Mebius  1   2 , Marjolein van Egmond  1   2   8
Affiliations

Fcα Receptor-1-Activated Monocytes Promote B Lymphocyte Migration and IgA Isotype Switching

Amélie V Bos et al. Int J Mol Sci. .

Abstract

Patients with inflammatory bowel disease (IBD) produce enhanced immunoglobulin A (IgA) against the microbiota compared to healthy individuals, which has been correlated with disease severity. Since IgA complexes can potently activate myeloid cells via the IgA receptor FcαRI (CD89), excessive IgA production may contribute to IBD pathology. However, the cellular mechanisms that contribute to dysregulated IgA production in IBD are poorly understood. Here, we demonstrate that intestinal FcαRI-expressing myeloid cells (i.e., monocytes and neutrophils) are in close contact with B lymphocytes in the lamina propria of IBD patients. Furthermore, stimulation of FcαRI-on monocytes triggered production of cytokines and chemokines that regulate B-cell differentiation and migration, including interleukin-6 (IL6), interleukin-10 (IL10), tumour necrosis factor-α (TNFα), a proliferation-inducing ligand (APRIL), and chemokine ligand-20 (CCL20). In vitro, these cytokines promoted IgA isotype switching in human B cells. Moreover, when naïve B lymphocytes were cultured in vitro in the presence of FcαRI-stimulated monocytes, enhanced IgA isotype switching was observed compared to B cells that were cultured with non-stimulated monocytes. Taken together, FcαRI-activated monocytes produced a cocktail of cytokines, as well as chemokines, that stimulated IgA switching in B cells, and close contact between B cells and myeloid cells was observed in the colons of IBD patients. As such, we hypothesize that, in IBD, IgA complexes activate myeloid cells, which in turn can result in excessive IgA production, likely contributing to disease pathology. Interrupting this loop may, therefore, represent a novel therapeutic strategy.

Keywords: CCL20; CD89; FcαRI; IBD; IgA; immunoglobulin A; inflammatory bowel disease; monocytes; myeloid cells.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Myeloid cells interact with B lymphocytes in the inflamed colon tissue of inflammatory bowel disease patients. Tissue was collected from either inflamed pathological regions or adjacent macroscopic nonpathological parts of the colon of inflammatory bowel disease (IBD) patients. (A) Quantification of the number of monocytes (identified as CD14+), (B) neutrophils (identified by anti-CD66+), and (C) B lymphocytes (identified as CD19+) in IBD patient biopsies from inflamed (red) or noninflamed (white) regions of the colon. (D) Example image for DNA (DAPI, blue), CD66b+ cells (green), and B lymphocytes (CD19, red) in inflamed colon biopsy of Crohn’s disease patient. Magnification (white square) was used for (E). (E,F) Single staining of DNA, CD66b+ neutrophils, and CD19+ cells of (E) Crohn’s disease (representative sample out of n = 5) and (F) ulcerative colitis (representative sample out of n = 3). Merged channels visualize the interaction (white arrows) between CD66b+ cells and CD19+ B lymphocytes. (G,H) Visualization for DNA, CD14+ monocytes (green), and CD19+ B lymphocytes in inflamed colon biopsy of patients with (G) Crohn’s disease (n = 5) or (H) ulcerative colitis (n = 3). Merged channels are demonstrated to visualize the interaction (white arrows) between CD14+ cells and B lymphocytes.
Figure 2
Figure 2
FcαRI-stimulated monocytes produce the chemokine CCL20 and attract B lymphocytes. (A,B) RNA sequencing of monocytes stimulated with either BSA- or IgA-coated (activating FcαRI) beads was performed. (A) Volcano plot of all genes expressed by monocytes with BSA- or IgA-coated bead stimulation. The x-axis represents log2 of the fold change, while the y-axis represents the local false discovery rate (lfdr). (B) Heat map of log-transformed RNA-seq counts of human peripheral monocytes after stimulation with BSA- or IgA-coated (activating FcαRI) beads. Genes above an lfdr of 0.05 are considered significant. Coloring represents log expression of expressed genes. (C–E) Peripheral monocytes were stimulated with BSA- or IgA-coated (activating FcαRI) beads for 24 h. Luminex was performed on the supernatant of stimulated monocytes to determine (C) C–C motif chemokine ligand 20 (CCL20). (D,E). Supernatants were placed in the bottom compartment of transwell chambers, while upper chambers contained peripheral B cells. Migration toward lower compartments was determined. (D) A representative experiment is shown (technical duplicate). Med: medium only as negative control. (E) Quantification of fold increase of B-cell migration toward supernatants of monocytes stimulated with BSA- or IgA-coated (activating FcαRI) beads. B-cell migration to medium was used to normalize for each donor was normalized. Data are presented as the mean ± SD. n.s. = not significant. Wilcoxon matched rank test, ** p < 0.01; Student’s t-test, * p < 0.05.
Figure 3
Figure 3
FcαRI-stimulated monocytes produce interleukin-6, interleukin-10, and tumor necrosis factor-α. Human peripheral monocytes were cultured with BSA- or IgA-coated (activating FcαRI) beads for 4 h. (A) Heat map of log-transformed RNA-seq counts of human peripheral monocytes stimulated with BSA- (n = 5) or IgA-coated (activating FcαRI) (n = 10) beads. Genes above an lfdr of 0.05 are considered significant. Coloring represents log expression of the expressed genes. Peripheral monocytes were cultured with BSA- (n = 10) or IgA-coated (activating FcαRI) (n = 10) beads (n = 10) for 24 h. Luminex was performed on supernatant of stimulated monocytes to determine (B) interleukin-6, (C) tumor necrosis factor-α (TNFα), (D) interleukin-10, (E) APRIL, (G) interleukin-7, and (H) interleukin-4 secretion. (F) Similarly, BAFF secretion was measured 24 h after BSA- or IgA-coated (activating FcαRI) bead stimulation (n = 3) using ELISA. Not detected protein (n.d.) is represented as zero. Data are presented as the mean ± SD. n.s. = not significant. Wilcoxon matched rank test, * p < 0.05, ** p < 0.01.
Figure 4
Figure 4
Exogenous recombinant cytokines induce IgA class switching in naïve B lymphocytes. Human naïve B cells were isolated from peripheral blood and cultured in the presence of T-cell-dependent stimuli, including interleukin-4, anti-CD40, and anti-IgM antibodies. In addition, B cells were supplemented with exogenous (A) interleukin-6, (B) interleukin-10, (C) tumor necrosis factor-α, or (D) APRIL. On day 7, IgA membrane expression was measured on B cells using flow cytometry (n = 3). Data are presented as the mean ± SD. Student’s t test, * p < 0.05.
Figure 5
Figure 5
FcαRI-stimulated monocytes induce IgA class switching in naïve B lymphocytes. Monocytes were stimulated with BSA- or IgA-coated (activating FcαRI) beads and cocultured with peripheral naïve B cells for 7 days in the presence of interleukin-4, anti-IgM, and anti-CD40 antibodies. (A) Representative histogram demonstrating IgA surface expression by B lymphocytes after coculture with monocytes treated without beads (non; white), with BSA-coated beads (gray) or IgA-coated beads (FcαRI) (red). (B) Quantification of the mean fluorescent intensity of IgA on B lymphocytes of six donors. (C) Representative ELISA demonstrating secreted IgA in the supernatants of co-cultured naïve B cells with monocytes treated without beads (non), with BSA-coated beads, or with IgA-coated beads (red). Naïve B cells in the absence of monocytes were cultured with beads as a negative control. (D) Quantification of IgA secretion by B cells in five donors. Donor numbers in (B,D) correspond. Not enough supernatant of d4 was available to analyze IgA secretion. Data are presented as the mean ± SD.
Figure 6
Figure 6
FcαRI-activated monocytes influence B lymphocyte migration and differentiation. Left panel: (1) During a mucosal infection, dIgA-opsonized bacteria are recognized by myeloid cells and cleared (2). (3) B-cell activation factors are temporarily increased; however, once the infection is cleared the process stops, and the system returns to homeostasis. Right panel: IBD is characterized by (4) a disrupted epithelial lining. (5) Excessive IgA complexes activate myeloid cells via FcαRI, which leads to production of cytokines that (6) promote B-cell migration to the site of inflammation via CCL20 and skewing into an IgA isotype. (7) In turn, this mechanism may promote enhanced IgA production and concomitant IgA complexes, thereby continuously stimulating newly recruited myeloid cells. As such, a perpetuating positive feedback-loop may be initiated that activates myeloid cells and promotes IgA B-cell differentiation.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

References

    1. Chen K., Magri G., Grasset E.K., Cerutti A. Rethinking mucosal antibody responses: IgM, IgG and IgD join IgA. Nat. Rev. Immunol. 2020;20:427–441. doi: 10.1038/s41577-019-0261-1. - DOI - PMC - PubMed
    1. Bunker J.J., Erickson S.A., Flynn T.M., Henry C., Koval J.C., Meisel M., Jabri B., Antonopoulos D.A., Wilson P.C., Bendelac A. Natural polyreactive IgA antibodies coat the intestinal microbiota. Science. 2017;358:eaan6619. doi: 10.1126/science.aan6619. - DOI - PMC - PubMed
    1. Lin Y.-L., Ip P.-P., Liao F. CCR6 Deficiency Impairs IgA Production and Dysregulates Antimicrobial Peptide Production, Altering the Intestinal Flora. Front. Immunol. 2017;8:805. doi: 10.3389/fimmu.2017.00805. - DOI - PMC - PubMed
    1. Zhiming W., Luman W., Tingting Q., Yiwei C. Chemokines and receptors in intestinal B lymphocytes. J. Leukoc. Biol. 2018;103:807–819. doi: 10.1002/JLB.1RU0717-299RR. - DOI - PubMed
    1. He B., Xu W., Santini P.A., Polydorides A.D., Chiu A., Estrella J., Shan M., Chadburn A., Villanacci V., Plebani A., et al. Intestinal Bacteria Trigger T Cell-Independent Immunoglobulin A2 Class Switching by Inducing Epithelial-Cell Secretion of the Cytokine APRIL. Immunity. 2007;26:812–826. doi: 10.1016/j.immuni.2007.04.014. - DOI - PubMed