Suppression of Th1- and Th2-type immune responses in infant mouse spleen after prenatal and postnatal exposure to low-level toluene and peptidoglycan.

The aim of the present study was to investigate the effect of low-level concentrations, under the occupational acceptable limits, of toluene exposure and peptidoglycan (PGN) stimulation on Th1/Th2 immunity in infant mice. Pregnant BALB/c mice and their offspring were exposed to low-level toluene inhalation (0, 5, and 50 ppm) for 4 wk (from the late prenatal stage to early postnatal stage) in a whole-body exposure chamber. Some of the pregnant mice and their offspring were stimulated with PGN during toluene exposure. We measured total immunoglobulins of different subclasses in plasma, and production and expression level of cytokines in the lung and spleen, and transcription factors related to Th1/Th2 immunity in the spleen of infant (3 wk old) mice. Exposure of mice to 5 or 50 ppm toluene resulted in increased immunoglobulin (Ig) G1 and decreased IgG2a and IgE antibodies in the plasma; significantly decreased T-bet, GATA-3, and Foxp3 mRNA in the spleen; and a tendency toward decreased interferon (IFN)-gamma mRNA in spleen. Exposure of mice to low-level toluene together with PGN stimulation resulted in decreased IgG1 as well as IgG2a antibodies in the plasma and Foxp3 mRNA in spleen as compared with control or PGN-treated mice. These findings suggest that low-level toluene exposure and PGN stimulation from the late prenatal to early postnatal stage suppressed the splenic parameter related to Th1/Th2 immunity in infant mice.