Cod’s Surprising Immune System

Norwegian research has revealed that the immune system of cod is very different from other fish and from mammals -- a discovery that may shed light on the human immune system as well. The discovery was made after scientists sequenced the entire cod genome.

Lacks part of immune system

Up to now, scientists have believed that all higher animals (including fish) share the same basic type of immune system as humans, assumed to have stemmed from a single common origin. Now it appears that cod are lacking in that part of the immune system that normally combats infection from bacteria and parasites.

"This was a very surprising finding," says Professor Kjetill S. Jakobsen, who headed the cod-sequencing project. "Conventional wisdom holds that cod should be dead. Yet it is very much alive -- a very successful species, in fact, quite widespread in the northern seas."

Alternative immunity

One of the genes that cod lack, known as MHC II, is responsible for detecting hostile microorganisms and initiating the immune response to fight off bacteria and parasites. Cod, however, have developed an entirely different way of battling bacteria and other infections. To compensate for a lack of MHC II, cod have a higher number of another gene, MHC I. Other parts of the cod immune system are different as well.

"This is a milestone in Norwegian biological research that will have both a social and an economic impact," emphasises Professor Jakobsen.

The results from the project have recently been published in the journal Nature.

New light on autoimmune disorders

"The unique immune system of cod gives us a new perspective on the human immune system as well," asserts Professor Jakobsen. "This discovery could also provide new insight into how to combat autoimmune disorders such as psoriasis, asthma and allergies."

The sequencing of the cod genome was hosted and coordinated by the Centre for Ecological and Evolutionary Synthesis (CEES), based at the Department of Biology, University of Oslo. Activities were carried out in collaboration with other Norwegian universities and with international research institutes in Norway and abroad.

Important for aquaculture industry

With the entire cod genome sequenced, scientists are able to identify genetic variations among individual cod. This will enhance their understanding of not only the immune system but also traits such as growth rate, sexual maturation, tolerance for temperature fluctuations, and oxygen uptake.

This kind of information will benefit both the aquaculture and fisheries industries. Fish farmers are looking to selectively breed cod that is adapted to production conditions -- fish that are both resistant to disease and an attractive commercial product. Additionally, vaccines can now be developed specifically for cod.

"The challenge now," says Anne Kjersti Fahlvik, Executive Director of the Research Council's Division for Innovation, "is to realise the true potential of detailed knowledge about the cod genome. This should be approached as a joint effort between the aquaculture industry and the relevant research communities."

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