Toll-like receptor 2 is expressed by alveolar epithelial cells type II and macrophages in the human lung.
The ability of the host to recognize pulmonary invasion by pathogenic organisms and establish an appropriate host response to infection requires innate immune defense mechanisms. Early bacterial clearance in the lung is mediated by alveolar macrophages (AM) and polymorphonuclear neutrophils. Additionally alveolar epithelial cells type II (AEC-II) may act as immunoregulatory cells. The toll-like receptors (TLR) are part of this innate immune defense, recognizing conserved patterns on microorganisms. Toll-like receptor 2 (TLR2) is crucial in detecting components of gram-positive bacteria and mycobacteria. Signals initiated by the interaction of TLR2 with bacterial components direct the subsequent inflammatory response. The detection of TLR2 mRNA in human lung tissue prompted us to localize the expression of mRNA and protein at the cellular level using a novel method for tissue fixation. We utilized HOPE-fixed lung specimen sections for targeting mRNA by in situ hybridization and protein by immunohistochemistry using the monoclonal antibody TL2.1. In normal lung areas the expression of TLR2 mRNA and protein was found to be located in cells resembling AEC-II and AM. Expression of mRNA was verified by RT-PCR and DNA sequencing. These results indicate a potential mechanism of increased immunosurveillance at the alveolar level controlling the localized infection.
Droemann
Daniel
D
Medical Clinic, Research Center Borstel, Parkallee 35, Germany.
Goldmann
Torsten
T
Branscheid
Detlev
D
Clark
Ryan
R
Dalhoff
Klaus
K
Zabel
Peter
P
Vollmer
Ekkehard
E
D004848:Epithelium / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007157:Immunologic Surveillance / Q000502:physiology; D017403:In Situ Hybridization; D008264:Macrophages / Q000166:cytology / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D015345:Oligonucleotide Probes / Q000737:chemistry; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016707:Tissue Fixation; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors
D008562:Membrane Glycoproteins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors