Human TLR1 plays an important role in host defense against Mycobacterium tuberculosis. Our aim was to analyze the association of the loss of TLR1 surface expression and TLR1 SNPs with susceptibility to TB. TLR1neg and TLR1pos cells from healthy individuals were identified by flow cytometry and compared by sequencing. TLR1 expression was measured using quantitative real-time PCR and immunoblotting. TLR1 SNP analyses of healthy individuals and TB patients from EU-C and Ghana were performed, and association of the TLR1 genotypes with increased risk of developing TB was statistically evaluated. Lack of TLR1 surface expression accompanied by impaired function was strongly associated with TLR1 SNP G743A. Genotyping of EU-C controls and TB patients revealed an association of TLR1 743A/1805G alleles [OR 2.37 (95% CI 1.13, 4.93), P=0.0219; OR 2.74 (95% CI 1.26, 6.05), P=0.0059] as well as TLR1neg 743AA/1805GG versus TLR1pos genotypes 743AG/1805TG [OR 4.98 (95% CI 1.64, 15.15), P=0.0034; OR 5.70 (95% CI 1.69, 20.35), P=0.0015] and 743AG + GG/1805TG + TT [OR 3.54 (95% CI 1.29, 9.90), P=0.0086; OR 4.17 (95% CI 1.52, 11.67), P=0.0025] with increased susceptibility to TB. No association of G743A with TB was found in Ghana as a result of a low frequency of genotype 743AA. Our data gain new insights in the role of TLR1 in M. tuberculosis defense and provide the first evidence that TLR1 variants are associated with susceptibility to TB in a low-incidence country.

Summary The role of neutrophils in the immune response has long been regarded as mainly phagocytic, but recent publications have indicated the production of several cytokines by polymorphonuclear leucocytes (PMN). The results of the individual reports, however, vary considerably. In this study, we established a cytokine profile of pure human neutrophils and demonstrated that minor contamination of peripheral blood mononuclear cells (PBMCs) in PMN preparations can lead to false‐positive results. In our hands, peripheral blood PMN fail to produce the pro‐inflammatory cytokines interleukin (IL)‐1β, IL‐6 and tumour necrosis factor‐α (TNF‐α). Instead, they secrete large amounts of the chemokine IL‐8 and the anti‐inflammatory IL‐1 receptor antagonist (IL‐1ra). Additionally, PMN preparations of a high purity show production of the chemokines macrophage inflammatory protein (MIP)‐1α, MIP‐1β and growth‐related oncogene‐α (GRO‐α), as well as macrophage colony‐stimulating factor (M‐CSF). The neutrophil therefore represents a novelty by producing the antagonist of IL‐1β (i.e. IL‐1ra) in the absence of IL‐1β itself. To support our results, we differentiated stem cells from human cord blood into PMN and monocytes, respectively. These in vitro‐differentiated PMN showed the same cytokine profile as peripheral blood PMN lacking IL‐1β, while differentiated monocytes produced the expected IL‐1β in addition to IL‐1ra. The clear anti‐inflammatory nature of their cytokine profile enables PMN to antagonize pro‐inflammatory signals in experimental conditions. It is therefore possible that PMN play a key role in immune regulation by counteracting a dysregulation of the inflammatory process. Clinical studies, in which administration of recombinant G‐CSF had a favourable effect on the outcome of severe infections and even sepsis without worsening inflammation, could thus be explained by our results.

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Summary Interleukin‐1β (IL‐1β) induces the expression of a variety of proteins responsible for acute inflammation and chronic inflammatory diseases. However, the molecular regulation of IL‐1β expression in myeloid differentiation has not been elucidated. In this study the chromatin structure of the IL‐1β promoter and the impact of methylation on IL‐1β expression in monocytic development were examined. The results revealed that the IL‐1β promoter was inaccessible in undifferentiated promyeloid HL‐60 cells but highly accessible in differentiated monocytic cells which additionally acquired the ability to produce IL‐1β. Accessibilities of differentiated cells were comparable to those of primary monocytes. Lipopolysaccharide (LPS) stimulation did not affect promoter accessibility in promyeloid and monocytic HL‐60 cells, demonstrating that the chromatin remodelling of the IL‐1β promoter depends on differentiation and not on the transcriptional status of the cell. Demethylation via 5‐aza‐2′‐deoxycytodine led to the induction of IL‐1β expression in undifferentiated and differentiated cells, which could be increased after LPS stimulation. Our data indicate that the IL‐1β promoter is reorganized into an open poised conformation during monopoiesis being a privilege of mature monocytes but not of the entire myeloid lineage. As a second mechanism, IL‐1β expression is regulated by methylation acting independently of the developmental stage of myeloid cells.