Environmentally induced changes in immunological function: acute and chronic effects of inhalation of tobacco smoke and other atmospheric contaminants in man and experimental animals

Attention is drawn to the long-term effects of atmospheric contaminants in general (and cigarette smoke in particular) on immunological control mechanisms that are accepted as playing a vital role in the maintenance of health. The review argues that a hostile environment within the respiratory tract created by inhalation of air contaminants compromises local immunological function in the short term, and ultimately depresses systemic immunological function. Whether such a decline in immunological homeostasis is due directly to toxicity, or indirectly to accelerated aging of susceptible elements of the immune system, is speculative. The changes observed in both man and experimental animals exposed for long periods to air contaminants in many respects parallel those associated with normal aging and may represent an acceleration of the process of senescence. Specific biological effects of smoking, air pollution and immune functions in man and animal models are reviewed. The precise mechanism(s) by which air contaminants affect immunological function remains speculative, but the relative resistance of specified-pathogen-free animals to these agents infers a central role for the hosts' normal bacterial flora in the process.