Compartmental analysis of resting and activated pulmonary natural killer cells

Conflicting reports exist regarding the activity of natural killer (NK) cells in resting lung. We speculated that use of cells from differing lung compartments in past studies might have contributed to these discrepancies. To address this issue, a compartmental analysis of relative NK activity of airspace (bronchoalveolar lavage) cells versus interstitial lung cells was conducted in guinea pigs. Non-pulmonary (spleen) cells were also assayed for NK activity. For assays, cells were obtained from each compartment in the same host, then assayed concomitantly using a chromium release assay with the tumor target cell line, K562. Virtually identical NK cell activity was demonstrated by cells derived from airspaces and lung interstitium. This activity was significantly less (p less than 0.05) than that of spleen cells, and its expression required periods of effector: target cell contact which were considerably longer (16 hr) than those needed for spleen cells (4 hr). Further experiments documented the capacity for augmentation of airspace NK cell activity by intratracheal instillation of interferon inducers poly I:C and carboxymethyl acridanone. We conclude that resting guinea pig pulmonary NK cells have low activity relative to systemic cells, that no significant difference in activity exists among NK cells in airspace and interstitial compartments, and that local activation of airspace NK cells is possible using intratracheal interferon inducers.