Evolution of the mammary gland from the innate immune system?

Authors

  • Claudia Vorbach,

    Corresponding author
    1. IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
    • IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Dr. Bohr Gasse 3-5, A-1030 Vienna, Austria.
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  • Mario R. Capecchi,

    1. Howard Hughes Medical Institute, Department of Human Genetics, University of Utah, Salt Lake City, UT
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  • Josef M. Penninger

    Corresponding author
    1. IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Vienna, Austria
    • IMBA, Institute of Molecular Biotechnology of the Austrian Academy of Sciences, Dr. Bohr Gasse 3-5, A-1030 Vienna, Austria.
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Abstract

The mammary gland is a skin gland unique to the class Mammalia. Despite a growing molecular and histological understanding of the development and physiology of the mammary gland, its functional and morphological origins have remained speculative. Numerous theories on the origin of the mammary gland and lactation exist. The purpose of the mammary gland is to provide the newborn with copious amounts of milk, a unique body fluid that has a dual role of nutrition and immunological protection. Interestingly, antimicrobial enzymes, such as xanthine oxidoreductase or lysozyme, are directly involved in the evolution of the nutritional aspect of milk. We outline that xanthine oxidoreductase evolved a dual role in the mammary gland and hence provide new evidence supporting the hypothesis that the nutritional function of the milk evolved subsequent to its protective function. Therefore, we postulate that the mammary gland evolved from the innate immune system. In addition, we suggest that lactation partly evolved as an inflammatory response to tissue damage and infection, and discuss the observation that the two signaling pathways, NF-kB and Jak/Stat, play central roles in inflammation as well as in lactation. BioEssays 28: 606–616, 2006. © 2006 Wiley Periodicals, Inc.

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