Methamidophos, a representative organophosphate insecticide, is regulated because of its severe neurotoxicity, but it is suspected of contaminating agricultural foods in many countries due to illicit use. To reveal unknown effects of methamidophos on human health, we evaluated the developmental immunotoxicity of methamidophos using a respiratory syncytial virus (RSV) infection mouse model. Pregnant mice were exposed to methamidophos (10 or 20 ppm) in their drinking water from gestation day 10 to weaning on postnatal day 21. Offsprings born to these dams were intranasally infected with RSV. The levels of interleukin-6 (IL-6) and interferon-gamma in the bronchoalveolar lavage fluids after infection were significantly decreased in offspring mice exposed to methamidophos. Treatment with methamidophos did not affect the pulmonary viral titers but suppressed moderately the inflammation of lung tissues of RSV-infected offspring, histopathologically. DNA microarray analysis revealed that gene expression of the cytokines in the lungs of offspring mice exposed to 20 ppm of methamidophos was apparently suppressed compared with the control. Methamidophos did not suppress IL-6 production in RSV-infected J774.1 cell cultures. Thus, exposure of the mother to methamidophos during pregnancy and nursing was suggested to cause an irregular immune response in the lung tissues in the offspring mice.

Beta-glucan (BG) is a representative pathogen-associated molecular pattern (PAMP) produced by pathogenic fungi. SCG is a BG obtained from Sparassis crispa, which stimulates splenocytes in DBA/2 mice to produce cytokines, such as GM-CSF, IFN-γ, and TNF-α. In the present study, we analyzed the molecular mechanism of SCG-mediated cytokine synthesis using cytocharasin D (CytD), an inhibitor of actin polymerization. It was found that GM-CSF and TNF-α synthesis of splenocytes stimulated with SCG, but not with lipopolysaccharide, was significantly enhanced in the presence of CytD. CRDO, partially hydrolyzed linear 1,3-BG curdlan, stimulated splenocytes of DBA/2 mice slightly to produce cytokines. CRDO, acting as an antagonist in the presence of SCG, changed to a strong agonist in the presence of CytD. CytD also enhanced cytokine synthesis of bone marrow-derived dendritic cells. Taken together, cytokine productivity of BG was significantly dependent on molecular weight, and CytD treatment is useful to enhance the sensitivity for analyzing the immunostimulating activity of BG in vitro.