Interferon-gamma (IFN-gamma) production by human T lymphocytes upon Legionella pneumophila stimulation in vitro.
In vitro immune responses to Legionella pneumophila were investigated. When human peripheral blood lymphocytes (PBL) from healthy volunteers were stimulated with formalin-killed L. pneumophila for 7 days in vitro, strong proliferative responses were observed. The responding cells were shown to be a CD4 T cell subset. It was also found that the CD4 T cells secreted significant amounts of IFN-gamma into the PBL culture supernatant. The production of IFN-gamma and IL-4 by PBL was measured semiquantitatively by reverse transcriptase-assisted polymerase chain reaction (RT-PCR) methods. Formalin-killed or live L. pneumophila-stimulated PBL expressed the mRNA for IFN-gamma but not the mRNA for IL-4. The results suggest that the whole bacterium, as opposed to the supernatant, predominantly stimulates Th1 type helper T cells. The cloned T cells specific for L. pneumophila expressed the mRNA for IFN-gamma but not for IL-4. In contrast to formalin-killed or live L. pneumophila stimulation, when PBL were stimulated with the bacterial culture supernatant, the proliferating T cells produced the mRNA for IL-4 as well as for IFN-gamma. A significant correlation between the proliferative response to formalin-killed L. pneumophila and IFN-gamma release in culture was observed (r = 0.6932, P < 0.001) in PBL from 30 healthy volunteers. From these in vitro studies, it is suggested that the whole L. pneumophila bacterium and their soluble antigens stimulate T cells in a manner which results in a different pattern of cytokine production.
Kitsukawa
K
K
Department of Immunology, National Institute of Neuroscience, NCNP, Tokyo, Japan.
Nakamoto
A
A
Koito
H
H
Matsuda
Y
Y
Saito
A
A
Yamamoto
H
H
D001483:Base Sequence; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D002455:Cell Division; D002478:Cells, Cultured; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism*; D015847:Interleukin-4 / Q000378:metabolism; D016952:Legionella pneumophila / Q000276:immunology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D018417:Th1 Cells / Q000276:immunology
D015847:Interleukin-4; D007371:Interferon-gamma