title: Toll-like receptor (TLR)-9 genetics and function in sarcoidosis.
abstract: Sarcoidosis is a systemic disorder characterized by the formation of non-caseating granulomas in variable organs. Toll-like receptor (TLR)-9 is important in the innate immune response against both Mycobacterium tuberculosis and Propionibacterium acnes, candidate causative agents in sarcoidosis. The aim of our study was to investigate possible genetic and functional differences in TLR-9 between patients and controls. TLR-9 single nucleotide polymorphisms were genotyped in 533 patients and divided into a study cohort and validation cohort and 185 healthy controls. Furthermore, part of the promotor as well as the entire coding region of the TLR-9 gene were sequenced in 20 patients in order to detect new mutations. No genetic differences were found between patients and controls. In order to test TLR-9 function, peripheral blood mononuclear cells (PBMCs) of 12 healthy controls and 12 sarcoidosis patients were stimulated with a TLR-9 agonist and the induction of interleukin (IL)-6, interferon (IFN)-γ and IL-23 was measured. Sarcoidosis patients produce significantly less IFN-γ upon stimulation with different stimuli. Regarding IL-23 production, a significant difference between patients and controls was found only after stimulation with the TLR-9 agonist. In conclusion, we did not find genetic differences in the TLR-9 gene between sarcoidosis patients and controls. Sarcoidosis patients produce less IFN-γ regardless of the stimulating agent, probably reflecting the anergic state often seen in their peripheral blood T lymphocytes. The differences in TLR-9-induced IL-23 production could indicate that functional defects in the TLR-9 pathway of sarcoidosis patients play a role in disease susceptibility or evolution.
authors.affiliation: Center for Interstitial Lung Diseases, Department of Pulmonology, St Antonius Hospital, Nieuwegein Division of Heart and Lungs, University Medical Center, Utrecht, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Veltkamp
authors.forename: C H M
authors.initials: CH
authors.lastname: Van Moorsel
authors.forename: G T
authors.initials: GT
authors.lastname: Rijkers
authors.forename: H J T
authors.initials: HJ
authors.lastname: Ruven
authors.forename: J M M
authors.initials: JM
authors.lastname: Van Den Bosch
authors.forename: J C
authors.initials: JC
authors.lastname: Grutters
mesh_terms: D002478:Cells, Cultured; D015331:Cohort Studies; D004252:DNA Mutational Analysis; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism; D053759:Interleukin-23 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D015810:Linkage Disequilibrium; D008297:Male; D009841:Oligonucleotides / Q000494:pharmacology; D010835:Phytohemagglutinins / Q000494:pharmacology; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012507:Sarcoidosis / Q000235:genetics* / Q000473:pathology; D051217:Toll-Like Receptor 9 / Q000819:agonists / Q000235:genetics* / Q000502:physiology
chemical_list: D053759:Interleukin-23; D015850:Interleukin-6; D009841:Oligonucleotides; D010835:Phytohemagglutinins; C495371:TLR9 protein, human; D051217:Toll-Like Receptor 9; D007371:Interferon-gamma