Effects of subchronic exposure to a mixture of O3, SO2, and (NH4)2SO4on host defenses of mice

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Abstract
Mice exposed 5 h/d, 5 d/wk up to 103 d, to 0.2 mg O 3 /m 3 or to a mixture of O 3 , 13.2 mg SO 2 /m 3 , and 1.04 mg (NH 4 ) 2 SO 4 aerosol/m 3 showed significantly greater susceptibility to group C streptococcal aerosol infection relative to filtered air controls. Pulmonary bactericidal activity by alveolar macrophages was significantly enhanced in the lungs of mice exposed to the mixture relative to those inhaling filtered air or O 3 alone. The total number and distribution of the free cells lavaged from the lungs, as well as cellular ATP levels, did not change due to the pollutant exposures. In vitro cytostasis in tumor target cells cocuitured with peritoneal macrophages from the exposed mice was significantly enhanced in the O 3 ‐exposed and in the mixture‐exposed treatment groups relative to controls and also in the mixture‐exposed relative to the O 3 ‐exposed group when a target‐to‐effector‐ceil ratio of 1:10 was used; no such effects were observed when this ratio was 1:20. Splenic T‐lymphocyte function, as measured by blastogenesis to mitogens and alloantigens, was affected by exposure to O 3 and/or the mixture, although the patterns of effects were qualitatively different. Splenic B‐cell function and macrophage antigen processing, as measured by the generation of antibody plaque‐forming cells, was unaffected by exposure.