Is <i>Xenopus</i> IgX an analog of IgA?

Mußmann, Rainer; Pasquier, Louis Du; Hsu, Ellen

doi:10.1002/eji.1830261205

Cited by 112 publications

(89 citation statements)

References 61 publications

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“…5), whereas IgM is expressed in nearly all tissues investigated. In accordance with previous observations (29,39), IgX was detected in the spleen, intestine, and stomach. Expression of IgF and IgD in the spleen is weaker than expression of IgM, IgX, and IgY, which probably explains the rareness of IgF and IgD EST clones in the NCBI EST database.…”

Section: Identification Of the Genomic Sequence Encoding Igm ( ) Igxsupporting

confidence: 93%

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Identification of IgF, a hinge-region-containing Ig class, and IgD inXenopus tropicalis

Zhao

Pan‐Hammarström

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

103

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Only three Ig isotypes, IgM, IgX, and IgY, were previously known in amphibians. Here, we describe a heavy-chain isotype in Xenopus tropicalis, IgF (encoded by C ), with only two constant region domains. IgF is similar to amphibian IgY in sequence, but the gene contains a hinge exon, making it the earliest example, in evolution, of an Ig isotype with a separately encoded genetic hinge. We also characterized a gene for the heavy chain of IgD, located immediately 3 of C , that shares features with the C␦ gene in fish and mammals. The latter gene contains eight constant-region-encoding exons and, unlike the chimeric splicing of CH1 onto the IgD heavy chain in teleost fish, it is expressed as a unique IgD heavy chain. The IgH locus of X. tropicalis shows a 5 V H-DH-JH-C -C␦-C -C -C 3 organization, suggesting that the mammalian and amphibian Ig heavy-chain loci share a common ancestor.amphibians ͉ antibody evolution

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Section: Identification Of the Genomic Sequence Encoding Igm ( ) Igxsupporting

confidence: 93%

“…cDNAs encoding the heavy chains of IgM, IgX, and IgY have all been cloned previously in Xenopus laevis (14,19,20). IgX has been considered to be an analogue of mammalian IgA because a large number of IgX-positive B cells are located in the gut epithelium (29). IgX is structurally distinct from mammalian IgA but is similar to chicken IgA (19,30).…”

mentioning

confidence: 99%

Identification of IgF, a hinge-region-containing Ig class, and IgD inXenopus tropicalis

Zhao

Pan‐Hammarström

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

103

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“…Xenopus IgY, which is consisted of four constant region domains, is regarded as a functional homologue of mammalian IgG (Warr et al, 1995). IgX has been considered to be an analogue of mammalian IgA because a large number of IgXpositive B cells were preferentially expressed in the gut epithelium (Mussmann et al, 1996). The Xenopous ␦ gene (IgD, possess eight Cdomains) locates in the same gene cluster, following immediately 3 end of the IgM gene, as in mammals (Ohta and Flajnik, 2006).…”

Section: Introductionmentioning

confidence: 99%

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

Wang

Nie

2009

Molecular Immunology

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“…15). Although all of these isotypes are expressed by lymphocytes in the spleen, the only conventional secondary lymphoid tissue in most cold-blooded vertebrates [i.e., no lymph nodes or Peyers patches (16)], there is also expression in other tissues, notably the small intestine (especially for IgX) and the liver (17). ''Resting'' B cells with surface expression of IgM are found in discrete splenic follicles, which are surrounded by a relatively diffuse T cell zone.…”

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confidence: 99%

IgD, like IgM, is a primordial immunoglobulin class perpetuated in most jawed vertebrates

Ohta

Flajnik²

2006

Proc. Natl. Acad. Sci. U.S.A.

195

138

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IgD has remained a mysterious Ig class and a bane to immunology students since its discovery >40 years ago. Its spotty occurrence in mammals and birds and the discovery of an isotype with similarities to IgD in bony fish are perplexing. We have identified IgD heavy (H) chain (␦) from the amphibian Xenopus tropicalis during examination of the IgH locus. The Xenopus ␦ gene is in the same position, immediately 3 of the IgM gene, as in mammals, and it is expressed only in the spleen at low levels, primarily as a transmembrane receptor by surface IgM ؉ cells. Our data suggest that frog IgD is expressed on mature B cells, like in mouse͞human. Unexpectedly, Xenopus IgD is orthologous to IgW, an Ig isotype found only in cartilaginous fish and lungfish, demonstrating that IgD͞W, like IgM, was present in the ancestor of all living jawed vertebrates. In striking contrast to IgM, IgD͞W is evolutionarily labile, showing many duplications͞deletions of domains, the presence of multiple splice forms, existence as predominantly a secretory or transmembrane form, or loss of the entire gene in a species-specific manner. Our study suggests that IgD͞W has played varied roles in different vertebrate taxa since the inception of the adaptive immune system, and it may have been preserved as a flexible locus over evolutionary time to complement steadfast IgM.evolution ͉ immune system S ince the pioneering work of comparative immunologists in the 1960s, IgM has been the Ig isotype believed to be primordial and most stable in vertebrate evolution (1). Despite differences in the degree of polymerization of the secretory form in different vertebrate groups (1, 2) and a major splice variant of the transmembrane (TM) form in teleost fish (3), IgM is renowned for its molecular, biochemical, and functional stability. Present in all living jawed vertebrates, IgM is the first isotype to be expressed both in ontogeny and during humoral adaptive immune responses and is found as the major TM receptor on the surface of both conventional and ''innate'' B cells (4).By contrast, IgD has remained an enigmatic isotype since its discovery long ago (5). Like IgM, IgD is expressed as a TM receptor on B cells of mouse and human, generated as a result of alternative splicing of pre-mRNA containing the transcribed variable (V) region and the IgM and IgD heavy (H) chain constant (C) regions ( and ␦, respectively). Because of its spotty presence in mammals and absence in birds, IgD was assumed to be a recently evolved isotype (6). However, the discovery of an isotype in ray-finned bony fish with sequence similarity to IgD (7) and its presence in some mammals previously believed to lack IgD (8) have greatly modified our view of Ig isotype evolution and suggested it may have arisen much earlier.A similarly strange phylogenetic jump surrounds the isotype IgW, which was discovered first in skates (9, 10) and later in sharks (11,12). The secreted version of the IgW H chain ( ) is present in long and short forms in all elasmobranchs tested to date, and the TM form is al...

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Is Xenopus IgX an analog of IgA?

Cited by 112 publications

References 61 publications

Identification of IgF, a hinge-region-containing Ig class, and IgD inXenopus tropicalis

Identification of IgF, a hinge-region-containing Ig class, and IgD inXenopus tropicalis

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

IgD, like IgM, is a primordial immunoglobulin class perpetuated in most jawed vertebrates

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