in Nature in August 2011
In the past 1 – 2 decades research at various institutes around the North Atlantic, also at Keldur, has shown that the immune system of Atlantic cod (Gadus morhua L.) is unusual compared to other fish species like, for example, the salmonids. Cod shows relatively poor or no antibody response to infection or vaccination (1) but is not particularly susceptible to infection. Cod seems to depend on efficient innate immune system and has a relatively high concentration of IgM and natural antibody activity in its serum (2). Scientists have speculated on the reason for the poor antibody response. In 2005 Prof. Lars Pilström (and others), Uppsala University suggested that the genetic loci MHC II, an essential element in adaptive immune response of vertebrates, was missing in cod, having unsuccessfully looked for its presence in cod (3).
This
theory has now been proved satisfactorily with the recent publication in
Nature by
Bastiaan Star and
Kjetill S. Jakobsen and others at the University of
Oslo. This work, based on the genome sequence of Atlantic cod,
demonstrated some interesting and unique features of cod’s immune system
including the absence of MHC II (4).
The paper is dedicated to the memory of L. Pilström and R.
J. M. Stet, which inspired their work to understand further the Atlantic
cod immune system.
The question remains whether cod has through some evolutionary pressure lost this important element concurrently with the reliance and development of other factors or whether the immune system of cod is an example of a parallel line of evolution from invertebrates to vertebrates.
1) Magnadóttir, B., Jónsdóttir, H., Helgason, S., Björnsson, B., Solem, S. T., Pilström. L. 2001. Immune parameters of immunized cod (Gadus morhua L.). Fish & Shellfish Immunology, 11: 75 – 89.
2) Magnadottir, B. Gudmundsdottir, S., Gudmundsdottir, B.K., Sigurdsson, H. (2009). Natural antibodies of cod (Gadus morhua L.): Specificity, activity and affinity. Comparative Biochemistry and Physiology B154, 309-316.
3) Pilstrom, L., Warr, G.W., Stromberg, S. 2005. Why is the antibody response of Atlantic cod so poor? The search for a genetic explanation. Fisheries Science, 71, 961-971.
Cod was immunized 3 times (arrows) with adjuvant (PBS), protein (LPH) or haptenated protein (TNP). In all groups, irrespective of the antigen used for immunization,
the specific antibody activity (anti-LPH) was low (<0.2)
and the non-specific antibody activity was high (0.4 - 0.6).