Aseptic loosening is a major complication of joint replacement surgery, characterized by periprosthetic osteolysis and chronic inflammation at the bone‑implant interface. Cells release chemokines, cytokines and other pro‑inflammatory substances that perpetuate inflammation reactions, while other particle‑stimulated macrophages promote osteoclastic bone resorption and impair bone formation. The present study investigated integrin and inflammatory cytokine expression patterns in RAW 264.7 cells treated with titanium (Ti) particles to elucidate the role of integrins in Ti particle‑mediated inflammatory osteolysis. Assessment was performed by reverse transcription‑quantitative PCR, western blotting, confocal immunofluorescence, flow cytometry and enzyme‑linked immunosorbent assays. Cell migration was evaluated by wound healing assay. It was found that Ti particles significantly induced integrin expression in RAW 264.7 cells, including upregulation of integrins β2 (CD18), aL (CD11a), aM (CD11b) and aX (CD11c). Ti particles also enhanced the expression of Toll‑like receptors (TLRs; TLR1, TLR2, TLR3 and TLR4) and triggered the release of inflammatory cytokines such as tumor necrosis factor α, interleukin (IL)‑1β, IL‑8 and IL‑12. Proteomics showed higher expression and activity levels of TLR2 and TLR4, along with their downstream signaling adaptors myeloid differentiation primary response protein 88 (MyD88) and Mal/TIR‑domain‑containing adapter protein (TIRAP), following Ti treatment. Additionally, Ti treatment significantly enhanced the migration rate of RAW 264.7 cells. The present findings indicated that Ti particles regulate the inflammatory response of RAW 264.7 cells in an in vitro aseptic loosening model by activating the TLR/TIRAP/MyD88 signaling pathway.

Airway epithelial cells (AEC) infected with SARS-CoV-2 may drive the dysfunction of macrophages during COVID-19. We hypothesized that the direct interaction of AEC with macrophages mediated by CD95/CD95L or indirect interaction mediated by IL-6 signaling are key steps for the COVID-19 severe acute inflammation. The interaction of macrophages with apoptotic and infected AEC increased CD95 and CD163 expression, and induced macrophage death. Macrophages exposed to tracheal aspirate with high IL-6 levels from intubated patients with COVID-19 or to recombinant human IL-6 exhibited decreased HLA-DR expression, increased CD95 and CD163 expression and IL-1β production. IL-6 effects on macrophages were prevented by both CD95/CD95L antagonist and by IL-6 receptor antagonist and IL-6 or CD95 deficient mice showed significant reduction of acute pulmonary inflammation post-infection. Our findings show a non-canonical CD95L-CD95 pathway that simultaneously drives both macrophage activation and dysfunction and point to CD95/CD95L axis as therapeutic target.
© 2023 The Authors.

Interleukin-12 (IL-12) is a potent driver of type 1 immunity. Paradoxically, in autoimmune conditions, including of the CNS, IL-12 reduces inflammation. The underlying mechanism behind these opposing properties and the involved cellular players remain elusive. Here we map IL-12 receptor (IL-12R) expression to NK and T cells as well as neurons and oligodendrocytes. Conditionally ablating the IL-12R across these cell types in adult mice and assessing their susceptibility to experimental autoimmune encephalomyelitis revealed that the neuroprotective role of IL-12 is mediated by neuroectoderm-derived cells, specifically neurons, and not immune cells. In human brain tissue from donors with multiple sclerosis, we observe an IL-12R distribution comparable to mice, suggesting similar mechanisms in mice and humans. Combining flow cytometry, bulk and single-nucleus RNA sequencing, we reveal an IL-12-induced neuroprotective tissue adaption preventing early neurodegeneration and sustaining trophic factor release during neuroinflammation, thereby maintaining CNS integrity in mice.
© 2023. The Author(s).

CTLA-4 exists as membrane (mCTLA-4) and soluble (sCTLA-4) forms. Here, we show that effector-type regulatory T cells (Tregs) are main sCTLA-4 producers in basal and inflammatory states with distinct kinetics upon TCR stimulation. Mice specifically deficient in sCTLA-4 production exhibited spontaneous activation of Th1, Th17, Tfh, and Tc1 cells, autoantibody and IgE production, M1-like macrophage polarization, and impaired wound healing. In contrast, sCTLA-4-intact mCTLA-4-deficient mice, when compared with double-deficient mice, developed milder systemic inflammation and showed predominant activation/differentiation of Th2, M2-like macrophages, and eosinophils. Consistently, recombinant sCTLA-4 inhibited in vitro differentiation of naïve T cells towards Th1 through CD80/CD86 blockade on antigen-presenting cells, but did not affect Th2 differentiation. Moreover, sCTLA-4-intact mCTLA-4-deficient Tregs effectively suppressed Th1-mediated experimental colitis whereas double-deficient Tregs did not. Thus, sCTLA-4 production by Tregs during chronic inflammation is instrumental in controlling type 1 immunity while allowing type 2 immunity to dominate and facilitate inflammation resolution.

Neutrophils accumulate in solid tumors, and their abundance correlates with poor prognosis. Neutrophils are not homogeneous, however, and could play different roles in cancer therapy. Here, we investigate the role of neutrophils in immunotherapy, leading to tumor control. We show that successful therapies acutely expanded tumor neutrophil numbers. This expansion could be attributed to a Sellhi state rather than to other neutrophils that accelerate tumor progression. Therapy-elicited neutrophils acquired an interferon gene signature, also seen in human patients, and appeared essential for successful therapy, as loss of the interferon-responsive transcription factor IRF1 in neutrophils led to failure of immunotherapy. The neutrophil response depended on key components of anti-tumor immunity, including BATF3-dependent DCs, IL-12, and IFNγ. In addition, we found that a therapy-elicited systemic neutrophil response positively correlated with disease outcome in lung cancer patients. Thus, we establish a crucial role of a neutrophil state in mediating effective cancer therapy.
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