Evidence for humoral immunodepression in NO2-exposed mice: influence of food restriction and stress.

The effects of food restriction or 20 ppm NO2 exposure on humoral immunity were investigated in normal and adrenalectomized C57Bl/6 mice. The thymic and splenic weights of sham-operated mice were similarly diminished after 4 days of NO2 exposure or 4 days of food depletion. The responses of corresponding adrenalectomized mice were less depressed. Undernutrition induced lymphoid organ involution and corticosteroids were partly involved. Plaque-forming cells (PFC) per spleen and per 10(6) cells were markedly depressed after 4 days of NO2 exposure, but less so after food deprivation. The same significant suppression of PFC was observed in adrenalectomized groups. Depression of humoral immunity was independent of stress-induced endogenous steroids. Moreover, NO2 had a specific effect on humoral immunodepression, food restriction being an associated factor.