Page 501 - Veterinary Immunology, 10th Edition

Two heavy chain allotypes (a and b) have been identified in all
VetBooks.ir three IgG classes. Allotype B1 is found on light chains of some cattle

but is relatively uncommon. IgA, IgM, and IgE also occur in cattle.
Cattle IgD may be expressed on B cells. About 95% of bovine

immunoglobulins have λ light chains.

Sheep

The immunoglobulin subclasses of sheep are similar to those of

cattle with IGHG genes coding for IgG1, IgG2, and IgG3. Some
sheep have an IgG1a allotype. An IGHD gene has been detected in
sheep. Three IgA heavy chain allotypes have been identified, as
have three IgE allotypes.

Pigs

Pigs have 10 immunoglobulin genes: IGHM, IGHD, six IGHG,
IGHE, and IGHA. Eleven pig Cγ gene sequences have been
described. These code for six IgG subclasses named IgG1 through

IgG6. There are two allelic forms of all of these subclasses except
IgG3. The differences between the alleles may be minor. For
b
a
example, IgG2 and IgG2 differ by only three amino acids. IgG3
has an extended hinge, is structurally unique, and appears to be the
b
most evolutionarily conserved porcine IgG. IgG5 differs most from
its allele, and its C 1 domain shares sequence homology with the
H
C 1 of IgG3. Some pigs may have two IGHG5 and two IGHG6 genes
H
but no IGHG2 or IGHG4. Other pigs may lack IgG4 or IgG6. IgG is
the predominant serum immunoglobulin, accounting for about 85%

of the total. IgM accounts for about 12% and dimeric IgA for about
3% of serum immunoglobulins. Pigs have a single IGHA gene with
b
a
two alleles. IgA differs from IgA by a 12-nucleotide deletion in the
hinge region owing to a mutation in its splice acceptor site. The
consequences of this are unclear. An IGHD gene has been identified
in pigs. Its first constant domain may be coded by either a C 1 δ
H
gene or by a C 1 µ gene! Thus pig IgD heavy chain transcripts may
H
contain either VDJ-CH1µ-CH2δ-CH3δ or VDJ-CH1δ-CH2δ-CH3δ.
This pattern has not been reported in other mammals. These two

genes, however, show almost 99% similarity, so the biological

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