Soluble Immune Complexes Shift the TLR-Induced Cytokine Production of Distinct Polarized Human Macrophage Subsets towards IL-10

Abstract

BackgroundCostimulation of murine macrophages with immune complexes (ICs) and TLR ligands leads to alternative activation. Studies on human myeloid cells, however, indicate that ICs induce an increased pro-inflammatory cytokine production. This study aimed to clarify the effect of ICs on the pro- versus anti-inflammatory profile of human polarized macrophages.Materials and MethodsMonocytes isolated from peripheral blood of healthy donors were polarized for four days with IFN-γ, IL-4, IL-10, GM-CSF, M-CSF, or LPS, in the presence or absence of heat aggregated gamma-globulins (HAGGs). Phenotypic polarization markers were measured by flow cytometry. Polarized macrophages were stimulated with HAGGs or immobilized IgG alone or in combination with TLR ligands. TNF, IL-6, IL-10, IL-12, and IL-23 were measured by Luminex and/or RT-qPCR.ResultsHAGGs did not modulate the phenotypic polarization and the cytokine production of macrophages. However, HAGGs significantly altered the TLR-induced cytokine production of all polarized macrophage subsets, with the exception of MΦIL-4. In particular, HAGGs consistently enhanced the TLR-induced IL-10 production in both classically and alternatively polarized macrophages (M1 and M2). The effect of HAGGs on TNF and IL-6 production was less pronounced and depended on the polarization status, while IL-23p19 and IL-12p35 expression was not affected. In contrast with HAGGs, immobilized IgG induced a strong upregulation of not only IL-10, but also TNF and IL-6.ConclusionHAGGs alone do not alter the phenotype and cytokine production of in vitro polarized human macrophages. In combination with TLR-ligands, however, HAGGs but not immobilized IgG shift the cytokine production of distinct macrophage subsets toward IL-10.

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

“…Moreover, importantly, our results are in very good accordance with a recent study showing that contrary to their widely accepted classification as anti-inflammatory M2 macrophages, human M-CSF-polarised macrophages promote inflammation, instead of having immunoregulatory properties upon co-stimulation by immobilised IgG and a toll-like receptor (TLR) ligand 32. These and the above-mentioned results,31 also obtained with immobilised IgG, suggest that the results we obtained with the immobilised ACPA-IC, that we chose to study because of their strong relevance to the RA pathophysiology, might be generalisable to all immobilised IgG containing IC. However, this remains to be demonstrated as the hierarchies of the inflammatory character of the cytokine response of the different macrophage subtypes obtained with other types of IC, formed with different or additional antibody isotypes, exhibiting a different solubility, or also including ligands for receptors of pathogen-associated molecular patterns, also remain to be investigated.…”

“…More generally, this observation, made in a very simplified model, confirms the major influence of macrophage microenvironment on their functional properties. Finally, for IFN-γ-polarised, IL-4-polarised and IL-10-polarised cells, concerning the ACPA-IC-induced secretion of IL-6, TNF-α and IL-10 and the corresponding TNF-α:IL-10 ratio, the hierarchies between macrophages subsets matched with those reported for macrophages stimulated by immobilised IgG 31. However and interestingly, given their phenotypic classification as IL-10-like immunoregulatory macrophages, in comparison with other macrophage subsets, including the phenotypically alike IL-10-polarised cells, the M-CSF-treated cells produced the highest levels of pro-inflammatory cytokines and the ratio between their TNF-α and IL-10 secretions was similar to that produced by the IFN-γ-polarised cells.…”

Evaluation of suppressive and pro-resolving effects of EPA and DHA in human primary monocytes and T-helper cells

“…Interference with the formation of the immunological synapse has substantial consequences for Ca 2+ -dependent cytoskeletal rearrangement, transcriptional regulation, and cytokine monocyte response by maintaining IFN ␥ in Th cells ( Fig. 2 ): IFN ␥ -polarized monocytes have been shown to preferably produce TNF-␣ and IL-6 in the presence of LPS ( 53 ). One group reported a negative association between the LPS-stimulated production of TNF-␣ and IL-6 by PBMC and n -3 PUFA intake, which, however, appeared to be characterized by a "U-shaped" dose-response relationship with IL-10 effects (reviewed in Ref.…”

Amelioration of Murine Passive Immune Thrombocytopenia by IVIg and a Therapeutic Monoclonal CD44 Antibody Does Not Require the Myd88 Signaling Pathway

“…As a variety of TLRs, including TLR2, 4, 7 and 9 can engage immune complexes [25–31], and CD44 can interact with TLR2 [34], TLR4 [35] and Myd88 [33], we next questioned whether the ameliorative abilities of IVIg or KM114 were reliant on Myd88 expression. The observation that anti-platelet antibody resulted in thrombocytopenia in Myd88 deficient mice suggests that, similar to TLR4, Myd88 expression is not required for the induction of thrombocytopenia in the murine ITP model.…”

“…We have previously demonstrated that IVIg may form immune complexes to exert its ameliorative effects [24]. Although TLRs are classically thought of as receptors for pathogen-associated molecular patterns, it has been demonstrated that both soluble and insoluble immune complexes have the ability to engage various TLRs, and regulate inflammation [25–31]. …”