Augmentation of NK cell activity by a circulating peptide isolated from the plasma of trauma patients.

Natural killer cell (NK) activity was assessed in patients with nonthermal injury. NK activity was assessed employing a standard 4-hour 51Cr release. Peripheral mononuclear cells from healthy human donors and trauma ward patients served as effector cells at three effector/target ratios. Labeled K562 erythroleukemia cells were used as targets. Multiple dilutions of crude and purified proteolysis inducing factor (PIF), isolated from three septic patients, were evaluated in comparison with other adjuvants. Greater augmentation of anti-K562 activity was obtained in long-term pretreatment of effector cells with adjuvants present as opposed to immediate NK assay. Untreated effectors from trauma patients demonstrated the least amount of baseline NK activity; however, a combination of PIF and interferon showed the greatest cytotoxicity. Untreated healthy cells exhibited a significant (p less than 0.001), twofold greater amount of cytotoxicity than untreated trauma cells. PIF enhances NK activity and may be key to mobilization of host defense in trauma.