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Discovery in the evolution of the immune system absorbing cells

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04.10.2006

The UAB has taken part in a research project that has just made a discovery that questions one of the paradigms of vertebrate immunology: that phagocytosis (the ability to "ingest" and destroy microbes) is performed mainly by "professional" phagocytic cells (macrophages, monocytes, granulocytes), while antibody-producing cells (B cells) are not capable of phagocytosis. The discovery affects fish and amphibians and will make it possible to produce a new type of vaccine for fish in the near future.

Led by Dr J Oriol Sunyer, of the Faculty of Veterinary Medicine at the University of Pennsylvania, and formed by researchers from Philadelphia, St Louis and Idaho (USA) and by Dr Lluís Tort of the Universitat Autònoma de Barcelona, the group has been able to show that B cells in fish as well as in amphibians are capable of strong phagocytosis both in in vivo and in vitro experiments. The work has been published in Nature Immunology, the most prestigious journal worldwide in the field of immunology.

According to Dr Sunyer, "this is important so that we can understand not only how the immune systems of fish and amphibians work but also the origin and composition of the immune systems of humans and mammals". The work concludes that there is an evolutionary relationship between macrophages and cells by which both cell types derive from a common, ancestral cell with functional properties of both cells. So though the B cells of lower vertebrates (fish and amphibians) are still capable of phagocytis while they are producing antibodies, the B cells of higher vertebrates are no longer capable of phagocytis. The latter specialise almost exclusively in functions of the adaptive immune response.

It is most probable that the less-elaborated, restrictive adaptive immune response of fish and amphibians makes the preservation of phagocytosis an evolutionary advantage to B cells in their defence against pathogens. One cannot forget that fish have had a significant evolutionary success, since nearly 50% of vertebrate species belong to this group and they are constantly in contact with a vast multitude of microorganisms in the water. According to Dr Sunyer, "From a practical perspective, this discovery will be used in the near future to produce a new design of vaccines for fish in order to stimulate phagocytosis in antibodies for B cells, increasing the effectiveness of the vaccine".

The study of comparative biology remains an important source of scientific knowledge. Several years ago, the same researchers demonstrated the great versatility and power of the innate immune response of the complement system in lower vertebrates, whereas mammals have developed greater effectiveness and specialisation in the adaptive mechanism of antibodies.

Octavi López Coronado | Source: alphagalileo
Further information: www.uab.es

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