Altered cellular immune function in the atelectatic lung.

Pulmonary atelectasis is common and may predispose the lung to infection. We have previously shown that atelectasis impairs alveolar macrophage antibacterial function. This study examines the effect of atelectasis on the cytotoxic function of lymphocytes harvested from the bronchoalveolar space of atelectatic lung segments by bronchoalveolar lavage. Specifically, we studied natural killer and lectin-dependent cell-mediated cytotoxicity in peripheral blood and bronchoalveolar lavage lymphocytes from the atelectatic lower lobes and contralateral normal lobes in a group of 8 dogs. We observed a decline of natural killer and lectin-dependent cell-mediated cytotoxicity to 62.7% and 61.5%, respectively, of preatelectasis control values in the affected lung lobes (p less than 0.01). Simultaneous measurements of cytotoxic activity of bronchoalveolar lavage lymphocytes harvested from the unaffected contralateral normal lungs were comparable with control values. On the other hand, natural killer and lectin-dependent cell-mediated cytotoxicity activities in peripheral blood lymphocytes were significantly increased in animals having right lower lobe atelectasis (166.7% and 154.7% of pretreated normal control, respectively, p less than 0.01). Atelectasis was also associated with an influx of polymorphonuclear leukocytes into the bronchoalveolar compartment. These findings confirm the presence of natural killer cells and cytotoxic lymphocytes in the bronchoalveolar compartment and demonstrate an atelectasis-induced impairment of local bronchoalveolar lymphocyte function. Such a dysfunction of local lung cellular host defenses may render the atelectatic lung susceptible to infection.