Differential cell reaction upon Toll-like receptor 4 and 9 activation in human alveolar and lung interstitial macrophages.
BACKGROUND
Investigations on pulmonary macrophages (MΦ) mostly focus on alveolar MΦ (AM) as a well-defined cell population. Characteristics of MΦ in the interstitium, referred to as lung interstitial MΦ (IM), are rather ill-defined. In this study we therefore aimed to elucidate differences between AM and IM obtained from human lung tissue.


METHODS
Human AM and IM were isolated from human non-tumor lung tissue from patients undergoing lung resection. Cell morphology was visualized using either light, electron or confocal microscopy. Phagocytic activity was analyzed by flow cytometry as well as confocal microscopy. Surface marker expression was measured by flow cytometry. Toll-like receptor (TLR) expression patterns as well as cytokine expression upon TLR4 or TLR9 stimulation were assessed by real time RT-PCR and cytokine protein production was measured using a fluorescent bead-based immunoassay.


RESULTS
IM were found to be smaller and morphologically more heterogeneous than AM, whereas phagocytic activity was similar in both cell types. HLA-DR expression was markedly higher in IM compared to AM. Although analysis of TLR expression profiles revealed no differences between the two cell populations, AM and IM clearly varied in cell reaction upon activation. Both MΦ populations were markedly activated by LPS as well as DNA isolated from attenuated mycobacterial strains (M. bovis H37Ra and BCG). Whereas AM expressed higher amounts of inflammatory cytokines upon activation, IM were more efficient in producing immunoregulatory cytokines, such as IL10, IL1ra, and IL6.


CONCLUSIONS
AM appear to be more effective as a non-specific first line of defence against inhaled pathogens, whereas IM show a more pronounced regulatory function. These dissimilarities should be taken into consideration in future studies on the role of human lung MΦ in the inflammatory response.
Hoppstädter
Jessica
J
Pharmaceutical Biology, Saarland University, Saarbrücken, Germany.
Diesel
Britta
B
Zarbock
Robert
R
Breinig
Tanja
T
Monz
Dominik
D
Koch
Marcus
M
Meyerhans
Andreas
A
Gortner
Ludwig
L
Lehr
Claus-Michael
CM
Huwer
Hanno
H
Kiemer
Alexandra K
AK
D002478:Cells, Cultured; D045604:Extracellular Fluid / Q000166:cytology* / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008168:Lung / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D008262:Macrophage Activation / Q000276:immunology; D016676:Macrophages, Alveolar / Q000166:cytology* / Q000378:metabolism* / Q000382:microbiology; D010587:Phagocytosis / Q000276:immunology; D051194:Toll-Like Receptor 1 / Q000378:metabolism; D051195:Toll-Like Receptor 2 / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000096:biosynthesis / Q000378:metabolism*; D051200:Toll-Like Receptor 8 / Q000378:metabolism; D051217:Toll-Like Receptor 9 / Q000096:biosynthesis / Q000378:metabolism*
D008024:Ligands; C495342:TLR2 protein, human; C495345:TLR4 protein, human; C495349:TLR8 protein, human; C495371:TLR9 protein, human; D051194:Toll-Like Receptor 1; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051200:Toll-Like Receptor 8; D051217:Toll-Like Receptor 9