Summary Lymphotoxin β-receptor (LTβR)-signalling orchestrates lymphoid neogenesis and subsequent tertiary lymphoid structures (TLS) 1 , 2 , associated with severe chronic inflammatory diseases spanning multiple organ systems 3 – 6 . How LTβR-signalling drives chronic tissue damage particularly in the lung, which mechanism(s) regulate this process, and whether LTβR-blockade might be of therapeutic value has remained unclear. Here we demonstrate increased expression of LTβR-ligands on adaptive and innate immune-cells, enhanced non-canonical NF-κB signalling and enriched LTβR-target gene expression in epithelial cells of lungs from patients with smoking-associated chronic obstructive pulmonary disease (COPD) and mice exposed to chronic cigarette smoke. Therapeutic inhibition of LTβR-signalling in young and aged mice disrupted smoking-related inducible bronchus-associated lymphoid tissue (iBALT), induced lung tissue regeneration, and reverted airway-fibrosis and systemic muscle wasting. Mechanistically, LTβR-signalling blockade dampened epithelial non-canonical NF-κB activation, reduced TGFβ-signalling in airways, induced regeneration by preventing epithelial cell-death and by activating Wnt/β-catenin-signalling in alveolar epithelial progenitor cells. These findings highlight that LTβR-signalling inhibition represents a viable therapeutic option combining anti-TLS, anti-apoptotic with tissue regenerative strategies.

The ubiquitously expressed RNA-binding proteins Roquin-1 and Roquin-2 are essential for appropriate immune cell function and postnatal survival of mice. Roquin proteins repress target mRNAs by recognizing secondary structures in their 3′-UTRs and by inducing mRNA decay. However, it is unknown if other cellular proteins contribute to target control. To identify cofactors of Roquin, we used RNA interference to screen~1500 genes involved in RNA-binding or mRNA degradation, and identified NUFIP2 as a cofactor of Roquin-induced mRNA decay. NUFIP2 binds directly and with high affinity to Roquin, which stabilizes NUFIP2 in cells. Post-transcriptional repression of human ICOS by endogenous Roquin proteins requires two neighboring non-canonical stem-loops in the ICOS 3′-UTR. This unconventional cis-element as well as another tandem loop known to confer Roquin-mediated regulation of the Ox40 3′-UTR, are bound cooperatively by Roquin and NUFIP2. NUFIP2 therefore emerges as a cofactor that contributes to mRNA target recognition by Roquin.

Extravasation of monocytes into tissue and to the site of injury is a fundamental immunological process, which requires rapid responses via post translational modifications (PTM) of proteins. Protein arginine methyltransferase 7 (PRMT7) is an epigenetic factor that has the capacity to mono-methylate histones on arginine residues. Here we show that in chronic obstructive pulmonary disease (COPD) patients, PRMT7 expression is elevated in the lung tissue and localized to the macrophages. In mouse models of COPD, lung fibrosis and skin injury, reduced expression of PRMT7 associates with decreased recruitment of monocytes to the site of injury and hence less severe symptoms. Mechanistically, activation of NF-κB/RelA in monocytes induces PRMT7 transcription and consequential mono-methylation of histones at the regulatory elements of RAP1A, which leads to increased transcription of this gene that is responsible for adhesion and migration of monocytes. Persistent monocyte-derived macrophage accumulation leads to ALOX5 over-expression and accumulation of its metabolite LTB4, which triggers expression of ACSL4 a ferroptosis promoting gene in lung epithelial cells. Conclusively, inhibition of arginine mono-methylation might offer targeted intervention in monocyte-driven inflammatory conditions that lead to extensive tissue damage if left untreated.

Influenza during pregnancy can affect the health of offspring in later life, among which neurocognitive disorders are among the best described. Here, we investigate whether maternal influenza infection has adverse effects on immune responses in offspring. We establish a two-hit mouse model to study the effect of maternal influenza A virus infection (first hit) on vulnerability of offspring to heterologous infections (second hit) in later life. Offspring born to influenza A virus infected mothers are stunted in growth and more vulnerable to heterologous infections (influenza B virus and MRSA) than those born to PBS- or poly(I:C)-treated mothers. Enhanced vulnerability to infection in neonates is associated with reduced haematopoetic development and immune responses. In particular, alveolar macrophages of offspring exposed to maternal influenza have reduced capacity to clear second hit pathogens. This impaired pathogen clearance is partially reversed by adoptive transfer of alveolar macrophages from healthy offspring born to uninfected dams. These findings suggest that maternal influenza infection may impair immune ontogeny and increase susceptibility to early life infections of offspring.