Why is the antibody response of Atlantic cod so poor? The search for a genetic explanation

Abstract

The immune system of the Atlantic cod (Gadus morhua L) is unusual in that it cannot produce a specific antibody response upon immunization. Despite this, the cod is not particularly susceptible to infectious disease in its normal environment. This review examines the potential genetic basis for the lack of a specific antibody response in the cod. The genetics of cod immunoglobulins are compared with those of other well-characterized teleost fish. A review of the evidence suggests that deficiencies in the number, structure, organization, diversity and expression of both Immunoglobulin (Ig) heavy and Ig light chain genes in cod cannot explain its unusual antibody response. It is concluded that a deficiency in cod major histocompatibility (MH) class II molecules is a prime suspect for the lack of a specific antibody response in cod, and that testing of this hypothesis must await future experimentation.

Diverse Immunoglobulin Light Chain Organizations in Fish Retain Potential to Revise B Cell Receptor Specificities

“…The relationship between type 1 and 3 has been suggested previously (for instance, see Ref. 25), but this study is the first to demonstrate the point in several species and by phylogenetic and genomic comparisons as well as taxonomic relationships. At this time, we failed to find a type 3 C region homolog in fugu (Acanthopterygii), but if in the future such sequences are found in non-Ostariophysi species, this would place the L1/L3 divergence at or before emergence of Euteleosts.…”

Functional characterization of IgM+ B cells and adaptive immunity in lumpfish (Cyclopterus lumpus L.)

“…It is well-known that fish B cells have MHC II and thus ability to present antigens, however, the mechanisms underlying the ability of fish B cells to present antigens to T cells is not clear. As there are teleost species, like Atlantic cod (Pilstrøm et al, 2005;Star et al, 2011), lacking MHC II, it will be interesting to investigate whether lumpfish have MHCII and if so, its presence on B cells.…”

“…The ability of teleosts to produce specific antibodies upon vaccination varies. This is exemplified by Atlantic salmon demonstrating a high specific antibody response upon vaccination while cod has a low response, possibly due to the lack of MHC II (Pilstrøm et al, 2005;Star et al, 2011).…”

Viral and bacterial diseases of Atlantic cod Gadus morhua, their prophylaxis and treatment: a review

“…Also, the difficulties finding MHC Class II genes in cod has been connected with a lack of Class II molecules, an inadequate antigen presentation and stimulation of T helper (TH2) cells and a corresponding absence of T-cell-dependent antibody responses (Pilström et al 2005). In this context, it is probably relevant that the Atlantic cod can mount a significant antibody response towards the LPS moiety of the Aeromonas salmonicida pathogen (supposed to be T cell independent), although immunisation with the LPS-containing Listonella anguillarum did not elicit similar antibody production (Lund et al 2006).…”