Background Previous studies have shown that constitutive and IgE-mediated histamine production by human lung mast cells is inhibited by a transferable factor produced by the airway epithelium. We have tested the hypothesis that a similar interaction exists between epithelial cell and mast cell lines. We have also investigated the effect of co-culture of epithelial cell lines and TH2 cells on interleukin (IL)-13 production.
Methods A549 or BEAS-2B cells were grown to confluence overnight. Media was removed and LAD2, HMC1.2 or human-derived ex-vivo T-cells added for 16 h. For transwell experiments epithelial cells were added to a 24-well plate, replaced with fresh media after 16 h and mast cells media added to the insert, maintaining the mast cell/epithelium/volume ratio. Wells, and transwell insert media, were then centrifuged, supernatants harvested and mediator release quantified by histamine or IL-13 ELISA.
Results Neither mast cell line consistently produced histamine in response to IgE and anti-IgE. Flow cytometry suggested that this was due to absence of the high-affinity IgE receptor FcεR1. Constitutive histamine production by HMC1.2 was reduced from 191 ± 13 ng/106 cells by 60.9% (95% CI 54.1, 67.8; p < 0.0001) when co-cultured with A549 and 21% (95% CI 14.2, 28.1; p < 0.0001) with BEAS-2B cells. Similar findings were seen with the LAD2 mast cell line. Constitutive IL-13 production by TH2 cells was reduced from 18000 ± 1800 pg/106 cells by 68.6% (95% CI 62.0, 75.1; P < 0.0001) by A549 and 59.9% (95% CI 53.3, 66.5; p < 0.0001) by BEAS-2B. Epithelial inhibition was similar when cells were separated by a transwell suggesting involvement of a transferable factor.
Conclusion Epithelial cell lines inhibit a range of asthma-related immunological responses, probably by producing an inhibitory substance.