Differential regulation of CD11b on γδ T cells and monocytes in response to unripe apple polyphenols

Leukocyte adhesion and migration are mediated partially by CD11b/CD18 (membrane-activated complex-1, CR3). Earlier studies have demonstrated a role for green tea polyphenols in down-regulating CD11b on CD8(+) T cells and monocytes. We have shown recently a stimulatory effect of unripe apple polyphenols (APP) on gamma delta T cells. Thus, we compared the effect of APP on bovine gamma delta T cell and monocyte CD11b expression. Purified bovine monocytes and monocyte-depleted PBLs were cultured with APP. CD11b levels decreased on monocytes in response to APP. In contrast, a gamma delta T cell subset responded to APP by up-regulating CD11b. The CD11b regulation was not seen on gamma delta T cells or monocytes treated with APP fractions depleted of tannins. The APP-induced down-regulation of CD11b on monocytes was inhibited by an anti-CD11b mAb, consistent with previous studies showing that polyphenols bind CD11b. As expected, the anti-CD11b mAb had no effect on the APP response in resting gamma delta T cells, as these cells lacked CD11b. Consistent with the changes in surface CD11b expression, APP-treated gamma delta T cells showed increased adherence to plastic, whereas monocyte adhesion was reduced. APP also induced cytokine gene expression in gamma delta T cells. Some polyphenols are thought of as antiinflammatory agents; however, these data, as well as other ongoing studies, indicate they have a proinflammatory effect on gamma delta T cells. In vivo, plant polyphenols may enhance gamma delta T cell migration and function at sites of inflammation, where they could induce rapid, immune-regulatory and innate-like immune responses.