Intracellular detection of interleukin 17 and other cytokines in human bronchoalveolar lavage fluid: a first assessment.

Increasing evidence links pulmonary pathology to cytokines determining an inflammatory environment in the lung. Detection of cells secreting specific cytokines in BALF could be helpful as a diagnostic tool but which cytokines to choose among their great variety may be the first question to solve. The aim of this study was to investigate the Th1, Th2 and Th17 cytokine profile in whole cells within the human bronchoalveolar lavage fluid (BALF) by flow cytometry, with a focus on interleukin (IL)-17-producing cells, in order to assess which cytokines might lend themselves as markers of disease in future studies. BALF and paired peripheral blood samples were collected from 52 patients admitted to hospital for pulmonary pathologies. Cells obtained from BALF and peripheral blood were incubated in vitro in the absence or presence of appropriate stimuli and analyzed for intracellular content of IL-4, -10, -12, -17, interferon (IFN)γ and tumor necrosis factor (TNF)α in association to expression of either HLA-DR or CD4. IL-17-secreting cells were further characterized. Production of IL-17 by unstimulated BALF cells could be detected in 2 of the 32 patients that could be examined; upon PMA/IM stimulation in vitro, IL-17 was produced by varying percentages of lymphocytes, mostly memory CD4(+) cells, in all BALF samples. IL-4 could be detected in a relatively high proportion of unstimulated HLA-DR(+/-), SSC(hi) cells, most probably granulocytes; IL-10 could be found mostly in macrophages in a number of the BALF samples analyzed. Finally, IFNγ and TNFα were only produced by lymphocytes after in vitro stimulation. This study shows that T cells producing IL-17 can be found in the lung of respiratory patients in the absence of ex vivo stimulation, making IL-17 a good candidate marker of specific pathologies of the lung. Upon stimulation, IL-17 production was accounted for by CD4(+) CD45RO(+) cells. Other cytokines are also discussed. An interesting cytokine secretion profile found in BALF from a patient with rheumatoid lung disease is also reported.