Changes in gene expression induced by apple polyphenol (APP)

γδ T cells are lymphocytes that function in both innate and adaptive immune responses, and our laboratory has previously reported that both bovine and human γδ T cells are primed for secondary responses by tannin components of the unripe apple peel (APP). In this report we began to investigate the mechanism by which priming occurs. We performed a microarray analysis on sorted bovine γδ T cells treated with APP and observed significant increases in transcripts encoding select inflammatory cytokines, such as GM-CSF, IL-8, and IL-17, but not markers of TCR stimulation such as IFNγ. When injected into the gut of mice, APP induced a robust influx of neutrophils into both the blood and peritoneum as measured by FACS. Importantly, both GM-CSF and IL-8 proteins were detected in these animals. Further studies were performed using the human γδ T cell-line MOLT-14, as large numbers of cells were required for subsequent experiments. Using these cells we found that both the GM-CSF and IL-8 mRNAs were significantly upregulated and stabilized in cells treated with APP. Finally, we show that the ERK1/2 MAPK pathway was activated in APP-treated MOLT-14 cells, and that this pathway plays a role in the mRNA stabilization we observed. Together, our data describe a unique inflammatory response in bovine, murine, and human γδ T cells in response to APP, and suggest that mRNA stability mechanisms could account for the priming phenotype we previously observed.APP has a distinctive gamma delta T cells specific priming activity. Keywords: comparison of 2 treatment types, tannin, gamma delta T cells To begin to understand the effects of APP in innate immunity, we investigated the global gene expression profiles of stimulated bovine gamma delta T cells. Peripheral blood from 2 neonatal bovine calves was collected. gamma delta T cells were sorted to >97% purity using a FACS Vantage. Cells were placed in culture and stimulated with either an aqueous extract of APP (42.2ug/ml) or PBS for 4 hours after which RNA was extracted and processed for microarray analysis following standard protocols from Affymetrix.