Cigarette smoking, air pollution, and immunity: a model system.

BALB/c mice were exposed to fresh cigarette smoke, a mixture of SO(2) (5 ppm) and CO (50 ppm), or both for periods up to 18 weeks. After varying exposure times, animals were intratracheally inoculated with 10(8) sheep erythrocytes and sacrificed 7 days later, during which time the various exposure regimes were continued. Plaque-forming-cell responses were measured in spleens and a pool of the cervical and mediastinal lymph nodes, together with serum hemagglutinating and hemolytic responses, and compared with those of age-matched control animals. Both the organ and serum responses exhibited stimulation in the early phase of exposure, before a depression with prolonged exposure. The greatest depression was seen in animals that had been chronically exposed to both fresh cigarette smoke and the gas mixture.