Background: Noninvasive detection of innate immune function such as the accumulation of neutrophils remains a challenge in many areas of clinical medicine. We hypothesized that granulocytes could generate volatile organic compounds.
Methods: To begin to test this, we developed a bioreactor and analytical GC-MS system to accurately identify and quantify gases in trace concentrations (parts per billion) emitted solely from cell/media culture. A human promyelocytic leukemia cell line, HL60, frequently used to assess neutrophil function, was grown in serum-free medium.
Results: HL60 cells released acetaldehyde and hexanaldehyde in a time-dependent manner. The mean +/- SD concentration of acetaldehyde in the headspace above the cultured cells following 4-, 24- and 48-h incubation was 157 +/- 13 ppbv, 490 +/- 99 ppbv, 698 +/- 87 ppbv. For hexanaldehyde these values were 1 +/- 0.3 ppbv, 8 +/- 2 ppbv, and 11 +/- 2 ppbv. In addition, our experimental system permitted us to identify confounding trace gas contaminants such as styrene.
Conclusion: This study demonstrates that human immune cells known to mimic the function of innate immune cells, like neutrophils, produce volatile gases that can be measured in vitro in trace amounts.