Among human macrophages polarised to different phenotypes, the M-CSF-oriented cells present the highest pro-inflammatory response to the rheumatoid arthritis-specific immune complexes containing ACPA.

In the inflamed synovium of patients with rheumatoid arthritis (RA), autoantibodies to citrullinated proteins (ACPA) probably form immune complexes (IC) on deposits of citrullinated fibrin. We showed that in vitro such ACPA-IC activate a pro-inflammatory cytokine response in M-CSF-differentiated macrophages. Our objective was to evaluate how macrophage polarisation influences this response. CD14-positive monocytes from healthy donors were cultured in the presence of M-CSF, IFN-γ, interleukin (IL)-4 or IL-10. Expression of markers specific for polarised macrophages was analysed by flow cytometry. Their cytokine secretion was prompted by in vitro generated autoantibodies to citrullinated proteins immune complexes (ACPA-IC) and assayed in the culture supernatants. IFN-γ-polarised cells exhibited high levels of CD64 and CD80. Low expression of CD14 and high expression of CD206 characterised the IL-4-polarised cells. Exposure to IL-10 or M-CSF raised the expression of CD14, CD32 and CD163. The two cell types lacked CD80 and exhibited similar expression of CD64, CD200R and CD206. In response to ACPA-IC, the secretion of IL-1β, IL-6 and IL-8 was similar among cells exposed to IFN-γ, IL-4 or IL-10. However, the later cells were associated with the highest IL-1Ra:IL-1β ratio and the lowest tumour necrosis factor (TNF)-α:IL-10 ratio. Conversely, M-CSF-exposed cells secreted the highest levels of pro-inflammatory cytokines, exhibited a high TNF-α:IL-10 ratio and the lowest IL-1Ra:IL-1β ratio. Despite their phenotypic similarity, IL-10-polarised and M-CSF-polarised macrophages clearly differ in their cytokine response to ACPA-IC. M-CSF-polarised cells exhibit the highest pro-inflammatory potential. Since M-CSF is abundant in the RA synovium, therein it probably drives macrophages towards a strong pro-inflammatory cytokine response to the locally formed ACPA-IC.

Clavel C ，Ceccato L ，Anquetil F ，Serre G ，Sebbag M ... -  《-》

IgM rheumatoid factor amplifies the inflammatory response of macrophages induced by the rheumatoid arthritis-specific immune complexes containing anticitrullinated protein antibodies.

Anticitrullinated protein antibodies (ACPA) are specifically associated with rheumatoid arthritis (RA) and produced in inflamed synovial membranes where citrullinated fibrin, their antigenic target, is abundant. We showed that immune complexes containing IgG ACPA (ACPA-IC) induce FcγR-mediated tumour necrosis factor (TNF)-α secretion in macrophages. Since IgM rheumatoid factor (RF), an autoantibody directed to the Fc fragment of IgG, is also produced and concentrated in the rheumatoid synovial tissue, we evaluated its influence on macrophage stimulation by ACPA-IC. With monocyte-derived macrophages from more than 40 healthy individuals and different human IgM cryoglobulins with RF activity, using a previously developed human in vitro model, we evaluated the effect of the incorporation of IgM RF into ACPA-IC. IgM RF induced an important amplification of the TNF-α secretion. This effect was not observed in monocytes and depended on an increase in the number of IgG-engaged FcγR. It extended to the secretion of interleukin (IL)-1β and IL-6, was paralleled by IL-8 secretion and was not associated with overwhelming secretion of IL-10 or IL-1Ra. Moreover, the RF-induced increased proinflammatory bioactivity of the cytokine response to ACPA-IC was confirmed by an enhanced, not entirely TNF-dependent, capacity of the secreted cytokine cocktail to prompt IL-6 secretion by RA synoviocytes. By showing that it can greatly enhance the proinflammatory cytokine response induced in macrophages by the RA-specific ACPA-IC, these results highlight a previously undescribed, FcγR-dependent strong proinflammatory potential of IgM RF. They clarify the pathophysiological link between the presence of ACPA and IgM RF, and RA severity.

Laurent L ，Anquetil F ，Clavel C ，Ndongo-Thiam N ，Offer G ，Miossec P ，Pasquali JL ，Sebbag M ，Serre G ... -  《-》

Fcγ receptor profile of monocytes and macrophages from rheumatoid arthritis patients and their response to immune complexes formed with autoantibodies to citrullinated proteins.

Laurent L ，Clavel C ，Lemaire O ，Anquetil F ，Cornillet M ，Zabraniecki L ，Nogueira L ，Fournié B ，Serre G ，Sebbag M ... -  《-》

Smoking, the HLA-DRB1 shared epitope and ACPA fine-specificity in Koreans with rheumatoid arthritis: evidence for more than one pathogenic pathway linking smoking to disease.

Fisher BA ，Bang SY ，Chowdhury M ，Lee HS ，Kim JH ，Charles P ，Venables P ，Bae SC ... -  《-》

Upregulation of interferon-γ response genes in monocytes and T cells identified by single-cell transcriptomics in patients with anti-citrullinated peptide antibody-positive early rheumatoid arthritis.

Our aim was to investigate the insufficiently understood differences in the immune system between anti-citrullinated peptide antibody (ACPA)-positive (ACPA+) and ACPA-negative (ACPA-) early rheumatoid arthritis (eRA) patients. We performed multiple cytokine assays using sera from drug-naïve ACPA+ and ACPA- eRA patients. Additionally, we conducted single-cell RNA sequencing of CD45+ cells from peripheral blood samples to analyze and compare the distribution and functional characteristics of the cell subsets based on the ACPA status. Serum concentrations of interferon-γ (IFN-γ) and interleukin (IL)-12 were higher in ACPA+ eRA than in ACPA- eRA. Single-cell transcriptome analysis of 37,318 cells identified 17 distinct cell types and revealed the expansion of IL1B+ proinflammatory monocytes, IL7R+ T cells, and CD8+ CCL4+ T cells in ACPA+ eRA. Furthermore, we observed an enrichment of IFN-γ response genes in nearly all monocytes and T cells of ACPA+ eRA subsets. Heightened interactions between IFN-γ and IFN-γ receptors were observed in ACPA+ eRA, particularly between monocytes and T cells. We examined IFITM2 and IFITM3 as potential key markers in ACPA+ eRA given their pronounced upregulation and association with the IFN response. Specifically, the expression of these genes was elevated in IL1B+ proinflammatory monocytes (likely M1 monocytes), correlating with serum IFN-γ levels. Compared to ACPA- eRA, ACPA+ eRA showed higher serum IFN-γ and IL-12 levels, upregulated IFN-γ response genes, and enhanced IFN-γ-driven monocyte-T cell interactions. These distinct immune features of the peripheral circulation in ACPA+ eRA suggest a role for type 1 helper T cell-related immunity in its pathogenesis.

Hong BK ，You S ，Kim JG ，Kim M ，Lee N ，Lee K ，Baek IP ，Ju JH ，Kim WU ，Kim HY ... -  《Frontiers in Immunology》