Effects of formaldehyde exposure on human NK cells in vitro

• Formaldehyde had a distinct toxicity on human NK cells.
• The minimum concentration of formaldehyde to induce toxicity was 800 μM.
• Formaldehyde can inhibit the adhering and cytotoxicity of NK cells.
• Formaldehyde can reduce the viability and perforin secretion of NK cells.

Natural killer (NK) cells play a pivotal role in human immunologic surveillance. Formaldehyde (FA), a ubiquitous environmental contaminant, has been classified as a carcinogen to humans. Although it is known that immune cells are sensitive to FA, so far little is known about how it's affecting the activity of human NK cells. To probe it, the primary human NK cells were treated with different concentrations of FA (3200, 1600, 800, 400, 200, 100, 50, and 0 μM) in vitro. The morphology, viability, apoptosis, cytotoxicity (killing tumor cell activity) and cytokine and cytolytic proteins secretion of NK cells were evaluated respectively. Our results reveal that FA could induce NK cells death obviously in a concentration-dependent manner. With the decreased concentrations of FA from 3200 μM to 800 μM, accordingly, the viability of NK cells increased from 65. 2 ± 12.1% to 78.48 ± 10.3% (p < 0.05), and the cytotoxicity of NK cells recovered from 29.2 ± 8.5% to 63.9 ± 5.9% (p < 0.05). The secretion of perforin was affected significantly by FA, whereas the secretion of IFN-γ and granzyme-B altered slightly. It is concluded that human NK cell is sensitive to FA, 800 μM may be a critical concentration of FA inhibiting the activity of human NK cell.