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Science 317 (5838): 678-681

Copyright © 2007 by the American Association for the Advancement of Science

Immune-like Phagocyte Activity in the Social Amoeba

Guokai Chen,1* Olga Zhuchenko,1* Adam Kuspa1,2,3{dagger}

Abstract: Social amoebae feed on bacteria in the soil but aggregate when starved to form a migrating slug. We describe a previously unknown cell type in the social amoeba, which appears to provide detoxification and immune-like functions and which we term sentinel (S) cells. S cells were observed to engulf bacteria and sequester toxins while circulating within the slug, eventually being sloughed off. A Toll/interleukin-1 receptor (TIR) domain protein, TirA, was also required for some S cell functions and for vegetative amoebae to feed on live bacteria. This apparent innate immune function in social amoebae, and the use of TirA for bacterial feeding, suggest an ancient cellular foraging mechanism that may have been adapted to defense functions well before the diversification of the animals.

1 Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
2 Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
3 Program in Developmental Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.

* These authors contributed equally to this work.

{dagger} To whom correspondence should be addressed. E-mail: akuspa{at}

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