engleski

Phenotypic Characterization of the Infiltrating Leukocyte Populations from the Lungs of C57Bl/6 Mice Infected with Legionella longbeachae

Previous studies showed that L. longbeachae serogroup 1 in a mouse model of lung infection has a high infectivity potential (LD50 ~104 CFU). Mice infected intratracheally with a sublethal dose (103 CFU) developed acute bronchopneumonia, but survived. We analyzed leukocyte populations attracted in the lungs of C57Bl/6 mice during the course of a sublethal infection with L. longbeachae serogroup 1. C57Bl/6 mice, were intratracheally inoculated with 103 CFU of L. longbeachae serogroup 1 (strain D4968). At different time points after infection leukocytes, obtained from lungs of infected animals were phenotypised using monoclonal antibody specific for the following leukocyte surface antigens: α -CD11b, α -CD80, α -CD86, α -CD3, α -CD4, α -CD8, α -NK1.1, α -CD19, α -CD69, α -CD45RB, and α -GR-1. L. longbeachae was stained with a rabbit polyclonal antibody. Three colour immunofluorescence analysis was performed by BD FACS Calibur™ flow cytometer using CellQuest™ software. For immunohistological procedures the lung sections were stained with different monoclonal antibodies (α -CD11b, α -CD4, α -CD8). We detected increase of CD11b+ cells in the lungs, 3 days post infection (~30% in uninfected mice vs ~70% 3 days after infection). Two populations of CD11b+ cells were found: CD11b+bright and CD11b+dimm cells (80% and 20% respectively). CD11b+bright cells were simultaneously positive for the granulocyte marker GR-1. An infiltration of CD11b+ cells in the peribronchial and perivascular areas of the lungs in the early phase of infection was observed. L. longbeachae was localised within CD11b positive cells. An accumulation of CD3+ cells and an inversion of the CD4/CD8 ratio in favor of CD8+ T lymphocytes was detected in the lungs of infected mice. On the contrary, B lymphocytes were significantly deprived from lung of infected mices during the first 3 days after infection and increase between day 7 and 21 post infection. Intratracheal infection of C57Bl/6 mice with L. longbeachae serogroup 1 induced bronchopneumonia that was accompanied by a massive recruitment of inflammatory cells in the lungs. Majority of the recruited cells expresed the CD11b antigen and coexpressed the granulocyte specific GR-1 antigen. 2 to 3 days after infection the lungs and hili were infiltrated with T lymphocytes, particularly with the CD8+ subset. B lymphocytes were deprived from the lungs and hili during the early phase of infection, but increased later on.

legionellosis; murine model; immunity

nije evidentirano