Loss of T follicular regulatory cell-derived IL-1R2 augments germinal center reactions via increased IL-1.

Inappropriate immune activity is key in the pathogenesis of multiple diseases, and it is typically driven by excess inflammation and/or autoimmunity. IL-1 is often the effector owing to its powerful role in both innate and adaptive immunity, and, thus, it is tightly controlled at multiple levels. IL-1R2 antagonizes IL-1, but effects of losing this regulation are unknown. We found that IL-1R2 resolves inflammation by rapidly scavenging free IL-1. Specific IL-1R2 loss in germinal center (GC) T follicular regulatory (Tfr) cells increased the GC response after a first, but not booster, immunization, with an increase in T follicular helper (Tfh) cells, GC B cells, and antigen-specific antibodies, which was reversed upon IL-1 blockade. However, IL-1 signaling is not obligate for GC reactions, as WT and Il1r1-/- mice showed equivalent phenotypes, suggesting that GC IL-1 is normally restrained by IL-1R2. Fascinatingly, germline Il1r2-/- mice did not show this phenotype, but conditional Il1r2 deletion in adulthood recapitulated it, implying that compensation during development counteracts IL-1R2 loss. Finally, patients with ulcerative colitis or Crohn's disease had lower serum IL-1R2. All together, we show that IL-1R2 controls important aspects of innate and adaptive immunity and that IL-1R2 level may contribute to human disease propensity and/or progression.

Human vascular smooth muscle cells utilise chymase for the atypical cleavage and activation of Interleukin-1ß.

BACKGROUND AND AIMS: Atherosclerosis and other cardiovascular diseases (CVD) are well established to be both instigated and worsened by inflammation. Indeed, CANTOS formally proved that targeting the inflammatory cytokine IL-1ß only could reduce both cardiovascular events and death. However, due to the central role of IL-1ß in host defence, blockade increased fatal infections, suggesting targeting key immune mediators over the long natural history of CVD is unsuitable. Thus, discovering alternative mechanisms that generate vascular inflammation may identify more actionable targets. METHODS: We used primary human VSMCs and a combination of biochemical, pharmacological and molecular biological techniques to generate the data. Human carotid atherosclerotic plaques were also assessed histologically. RESULTS: We showed that VSMCs expressed and efficiently processed pro-IL-1ß to the active form after receiving a single stimulus via IL-1R1 or TLR4. Importantly, pro-IL-1ß processing did not utilise inflammasomes or caspases. Unusually, we found that cathepsin C-activated chymase was responsible for cleaving IL-1ß in VSMCs, and provided evidence for chymase expression in cultured VSMCs and in the fibrous cap of human plaques. Chymase also efficiently cleaved and activated recombinant pro-IL-1ß. CONCLUSIONS: Thus, VSMCs are efficient activators of IL-1ß that do not use canonical inflammasomes or caspases. Hence, this alternative pathway could be targeted for long-term treatment of CVDs, as it is not central to everyday host defence.

Evidence of a genetic background predisposing to complex regional pain syndrome type 1.

BACKGROUND: Complex regional pain syndrome type 1 (CRPS-1) is a rare, disabling and sometimes chronic disorder usually arising after a trauma. This exploratory study examined whether patients with chronic CRPS-1 have a different genetic profile compared with those who do not have the condition. METHODS: Exome sequencing was performed to seek altered non-synonymous SNP allele frequencies in a discovery cohort of well-characterised patients with chronic CRPS-1 (n=34) compared with population databases. Identified SNP alleles were confirmed by Sanger sequencing and sought in a replication cohort (n=50). Gene expression of peripheral blood macrophages was assessed. RESULTS: In the discovery cohort, the rare allele frequencies of four non-synonymous SNPs were statistically increased. The replication cohort confirmed this finding. In a chronic pain cohort, these alleles were not overexpressed. In total, 25 out of 84 (29.8%) patients with CRPS-1 expressed a rare allele. The SNPs were rs41289586 in ANO10, rs28360457 in P2RX7, rs1126930 in PRKAG1 and rs80308281 in SLC12A9. Males were more likely than females to have a rare SNP allele, 8 out of 14 (57.1%) vs 17 out of 70 (24.3%) (Fisher's p=0.023). ANO10, P2RX7, PRKAG1 and SLC12A9 were all expressed in macrophages from healthy human controls. CONCLUSION: A single SNP in each of the genes ANO10, P2RX7, PRKAG1 and SLC12A9 was associated with developing chronic CRPS-1, with more males than females expressing these rare alleles. Our work suggests the possibility that a permissive genetic background is an important factor in the development of CRPS-1.

The common IL1A single nucleotide polymorphism rs17561 is a hypomorphic mutation that significantly reduces interleukin-1α release from human blood cells.

Interleukin-1 alpha (IL-1α) is a powerful cytokine that drives inflammation and modulates adaptive immunity. Due to these powerful effects, IL-1α is controlled at multiple levels from transcription to cleavage and release from the cell. Genome-wide association studies can identify loci that drive important diseases, although often the functional effect of the variant on phenotype remains unknown or small, with most risk variants in non-coding regions. We find that the common variant rs17561 changes a conserved amino acid in the central region of IL-1α linking the pro piece to the cytokine domain. Using a recall-by-genotype study and whole blood stimulation, we find that minor allele homozygotes release ~50% less IL-1α than the major allele, with IL-1ß release equivalent. IL-1α transcript level was identical between groups, implying a post-transcriptional effect, whilst cleavage of recombinant pro-IL-1α by multiple proteases was also equivalent for both forms. Importantly, transfected macrophages also release less minor allele IL-1α upon inflammasome activation, revealing that reduced secretion is directly caused by the missense amino acid substitution and more minor allele IL-1α was retained within the cell. Thus, rs17561 represents a very common hypomorphic mutation in IL-1α. We believe this novel data will be important for determining the potential contribution of IL-1α to disease and/or physiological processes, for example, by Mendelian randomisation, and may aid patient stratification when considering anti-IL-1 therapies.