Page 533 - Veterinary Immunology, 10th Edition

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FIG. 17.12 The lymphoid organs where gene recombination, gene
conversion, and somatic mutation occur.

Pigs

Pigs have about 20 IGHV genes, two IGHD genes, and a single
germline IGHJ gene. Early in fetal life, the pig uses only four or five
IGHV genes, and their early repertoire consists of only 8 to 10
combinations. Later in fetal life, this restricted repertoire is
compensated for by early TdT activity and extensive, in frame, N-

region addition leading to significant junctional diversity. V use is
H
independent of gene position, but three IGHV genes account for

40% of the pre-immune repertoire and six genes for 70%. The
neonatal piglet has very little diversity available at birth.
Pigs produce kappa and lambda light chains in approximately
equal amounts. They have 23 IGLV genes of which 10 are

functional. The constant loci consist of three tandem IGLJ-IGLC
cassettes plus a fourth downstream IGLJ gene. The kappa locus
contains at least 14 IGKV genes of which nine are functional, five
IGKJ genes and one IGKC gene.

Unlike the great combinatorial diversity seen in humans, the
early pre-immune antibody repertoire in pigs is relatively limited
with only 224 variants accounting for almost 100% of the
immunoglobulin variation. Most of this diversity is accounted for

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