Amoebas eat cells alive and leave their prey for dead
New findings published in Nature have changed what scientists thought about amoebas – specifically the Entamoeba histolytica amoeba. E. histolytica infections occur in approximately 50 million people and kill almost 100,000 people a year worldwide, mostly in developing countries. New treatments to prevent or cure this infection are needed.
Scientists had thought that this amoeba killed its prey (human intestinal cells) and ate them after they were dead. A postdoc at the University of Virginia, Katherine Ralston, showed otherwise.
Using fluorescently labeled cells and amoebas, Dr. Ralston noticed that the amoeba actually nibbles on the cells, taking small chunks out of the cell membrane and ingesting them. When the cell membrane has been destroyed and the cell has died, the amoeba moves on to another live cell, leaving the dead cell behind.
What does all of this mean? Scientists are still trying to understand that question, but it could provide some understanding of how foreign cells can evade the human immune system. One suggestion is that the amoeba leaves the remaining uneaten part of the cell as a decoy for one of the immune cell types, the macrophage, to clean up. This would keep the immune system busy while the amoeba continues to gain sustenance from other living cells.
This work may lead to new ways of thinking about the immune system. By understanding this mechanism, maybe new treatments can be developed to beat amoebas – or other invading organisms – at their own game. This could be useful for developing new preventative methods, or better immune stimulating drugs.
K.S. Ralson et al., “Trogocytosis by Entamoeba histolytica contributes to cell killing and tissue invasion,” Nature, doi:10.1038/nature13242, 2014.
Drawing by Pearson Scott Foresman [Public domain], via Wikimedia Commons
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