Effects of the Blue-Green Algae Aphanizomenon flos-aquae (L.) Ralphs on Human Natural Killer Cells
Author(s): Raffi Manoukin, Monica Citton, Patricia Huerta, Barbara Rhode, Christian Drapeau, Gitte S. Jensen
In a double-blinded cross-over study, we evaluated the immediate (two hours) effect of Aphanizomenon flos-aqua (L.) Ralphs (AFA) on five normal healthy volunteers by comparing % NK cells in peripheral blood. The same volunteers consumed AFA and placebo on different days, and experiments were always done in the morning. The AFA dose was 1.5 g of freeze-dried algae. We found no differences in % NK cells after ingestion of placebo. In the same individuals, AFA ingestion resulted in a significant decrease if % NK cell in the circulation within two hours after AFA ingestion. The decreased level of NK cells was on average 63% of the starting percentage of circulating NK cells. In two donors, the expression of adhesion molecules of NK cells was tested after NK ingestion. The circulating NK cells showed increased expression of the adhesion receptor CD11b and the homing molecule L-selectin after AFA ingestion. We interpret this as a biological effect from yet uncharacterized molecular components within the AFA algae that regulates the recruitment of NK cells from blood into tissue. The observations may support previous speculations on the presence of neuropeptides or cytokine-like molecules within AFA. The rapid effect could indicate a direct action on NK cells, leading to increased ability to adhere to endothelium and migrate into lymphoid tissue. Absorbed components within ingested AFA could rapidly affect the endothelium in the gut mucosal-associated lymphoid tissue, leading to increased recruitment of specific cell subsets from blood. Alternatively, the action could occur via nerve stimulus to lymphoid tissue, thereby changing the tissue microenvironment, altering the endothelium or leading to secretion of chemokines. Both mechanisms would ultimately lead to an increased recruitment of NK cells from the blood, which after two hours leads to a measurable decrease of % NK cells in the circulation. Further studies are in progress to elucidate the short term and long term effects of AFA consumption on the human immune systems.