The role of CD8+ Th2 lymphocytes in the development of smoking-related lung damage.

There is increasing evidence for the existence of different subsets of CD8+ T lymphocytes in humans, according to their cytokine secretion profile. Resistance or susceptibility to infections and the outcome of some inflammatory processes may depend on the lymphokine profile which predominates. We show one consequence of the switching of a host CD8+ T cell response from the Th1 effector function to the Th2 pattern in relation to the exposure to a common toxicant and its pathogenetic implications. Chronic obstructive bronchitis is a pulmonary disease characterized by airway inflammation with predominance of CD8+ T lymphocytes, mucus hypersecretion, repeated airway infections, and decline in lung function. Though smoking-related, it affects only a portion of smokers. The results of this study, comparing the functional characteristics of CD8+ T cell clones from smokers with the disease, unaffected smokers and healthy individuals, indicate that the smokers who have a predominance of CD8+ T lymphocytes of the Th2 phenotype may be predisposed to develop more severe smoking-induced lung damage, with chronic airway inflammation, repeated infections and persistent airflow obstruction.