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Molecular characterization of VDJ transcripts from a newborn piglet
Author(s) -
SUN J.,
BUTLER J. E.
Publication year - 1996
Publication title -
immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.297
H-Index - 133
eISSN - 1365-2567
pISSN - 0019-2805
DOI - 10.1046/j.1365-2567.1996.d01-676.x
Subject(s) - germline , biology , gene , somatic cell , microbiology and biotechnology , germline mutation , genetics , open reading frame , genome , mutation , peptide sequence
The sequences of 42 transcripts, expressed with IgM, IgG and IgA and cloned from the mesenteric lymph node of a newborn piglet, are described. Forty transcripts used either D H A and D H B and their FR4 were identical to the single swine germline J H . The low frequency of somatic mutation made it possible to identify 35/41 as originating from five putative germline V H genes, of which V H A, V H B and V H C accounted for > 85%. The remaining six transcripts were hybrids of these five germline genes. The most 3′ functional V H gene (V H 2 = V H B) was the only one exclusively expressed with IgM although V H A, of unknown location in the genome, accounted for half of all transcripts. Junctional diversity in CDR3 was extensive and asymmetrical, in that D–J joining contributed more diversity than V–DJ joining. Reading frame II was used twice as frequently as frame III and the CDR3 generated using the former would have a higher expected R/S ratio. This study indicated that the expressed V H repertoire of the newborn piglet is restricted and nearly germline although junctional diversity is mature and better developed than in fetal mice. The hybrid clones suggest that swine compensate for their < 20 V H genes and single J H by using somatic gene conversion. There was no evidence for exclusive or preferential expression of the most 3′ V H gene as occurs in chickens and rabbits respectively, and switching to downstream constant regions probably occurs in utero , even in the theoretical absence of environmental antigens and maternal regulatory molecules. Preferential V H A expression is probably a selection phenomenon.