Organic dust-induced interleukin-12 production activates T- and natural killer cells

Exposure in swine confinement buildings causes intense airway inflammation and lymphocyte activation, as assessed by bronchoalveolar lavage. To further clarify the T-cell activation, the present in vitro study focused on intracellular cytokine production following exposure to organic dust from swine houses. Whole blood from healthy donors was incubated with swine dust, phytohaemagglutinin (positive control) or Roswell Park Memorial Institute 1640 medium (negative control), and the production of intracellular interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha, interleukin (IL)4 and IL-12 was analysed by flow cytometry. Cells were double stained for specific cell surface markers on T-cells (CD3+, CD4+, CD8+), natural killer (NK) cells (CD56+ CD16+) and monocytes (defined as CD14+ cells). Following 1 h of incubation of whole blood with swine dust, CD14+ cells produced high levels of TNF-alpha and IL-12, whereas CD3+, CD4+ and CD8+ T-cells and CD56+ CD16+ NK cells required a longer incubation time (22 h) to produce IFN-gamma and TNF-alpha. When antibodies that block the IL-12 receptor were added to whole blood incubated with swine dust, NK cell production of IFN-gamma was attenuated and CD69 expression on CD3+ cells decreased. In conclusion, this study indicates that swine dust can, at least in part, stimulate phagocytic cells to activate natural killer cells and T-lymphocytes through the production of interleukin-12.