Immunoglobulins of the non-galliform birds: Antibody expression and repertoire in the duck

Abstract

Galliform and non-galliform birds express three immunoglobulin isotypes, IgM, IgA and IgY. Beyond this we should not generalize because differences in gene organization may have functional consequences reflected in the immune response. At present, studies on non-galliform birds are largely restricted to ducks. Ducks express an alternatively spliced form of their IgY heavy chain (upsilon) gene, the IgY(DeltaFc), that lacks the Fc region and Fc-associated secondary effector functions. It is not known how common the expression of the IgY(DeltaFc) is among birds, nor the functional consequences. It is also not known whether the unusual organization of the duck IgH locus, also shared with the chicken, having the gene order of mu, alpha and upsilon, with alpha inverted in the locus, is unique to the galloanseriform lineage. Ducks, like chickens, have a single immunoglobulin light chain of the lambda (lambda) type. Evidence suggests that ducks, like chickens, generate their immunoglobulin repertoire through a single functional rearrangement of the variable (V) region, and generate diversity through gene conversion from a pool of pseudogenes. In Southern blots of germline and rearranged bursal DNA, both the heavy and light chain loci of ducks appear to each undergo one major rearrangement event. For both heavy and light chains, the functional V region element and the pseudogenes appear to consist of a single gene family. Further analysis of 26 heavy chain joining (JH) and 27 light chain JL segments shows there is use of a single J segment in ducks, which is diversified presumably through somatic mutations and gene conversion events. Despite this limitation on the rearrangement of immunoglobulin genes, analysis of 26 DH and 122 VL sequences suggests that extensive sequence diversity is generated.

IgM, IgD and IgY and their expression pattern in the Chinese soft-shelled turtle Pelodiscus sinensis

“…To our knowledge, IgY has previously been described only in birds and amphibians (Warr et al, 1995;Lundgvist et al, 2006), and its discovery in the turtle fills up the gap in the knowledge IgY in vertebrates.…”

“…The basic structure of the Igs is composed of a four-chain unit in which two heavy chains are associated with two light chains, and the constant domains define the isotype of Ig heavy chains (Flajnik, 2002). In mammals, five Ig isotypes, IgM, IgD, IgG, IgA and IgE have been reported, and three isotypes, IgM, IgY and IgA in avians (Lundgvist et al, 2006;Schaerlinger et al, 2008). However in anuran amphibians, five isotypes have so far been reported, namely, IgM, IgY, IgX, IgD and IgF, and studies on amphibian Igs have mostly resulted from the model animal Xenopus.…”

Different outcomes of infection of chickens and ducks with a duck-origin H9N2 influenza A virus

“…It was consistent with previous studies reporting that ducks typically generated poor antibody responses to influenza compared with mammals or even chickens, and further studies showed immunoglobulin genetics contributed to poor antibody responses to influenza infection or vaccination. Evidence also suggested that lack of secondary immune responses appeared to be a general feature of duck antibody responses (Kida et al, 1980;Lundqvist et al, 2006). Several inactivated influenza vaccines are currently used for controlling avian influenza in the laboratory and field studies (Tian et al, 2005;Nomura et al, 2012;).…”

Ig heavy chain genes and their locus in grass carp Ctenopharyngodon idella

“…In duck billed platypus (Ornithorhynchus anatinus), a much more complicated IgH locus has recently been revealed [3,4], with the finding of two IgA isotypes [5] and a new Ig isotype, IgO [4], which is considered to be a remaining copy of IgY in monotremes [5]. Avian species are reported to have IgM and IgA, and also IgY in duck [6,7], but as IgG in chicken which, from a phylogenetic perspective, is equidistant from mammalian IgG and IgE and which in birds has sometimes been referred to as IgY [8]. Recently, IgM, IgD and IgY genes have been identified in reptile, the green anole lizard (Anolis carolinensis) with available genome data [9], and also in an economically important species [10].…”