Page 321 - Veterinary Immunology, 10th Edition

However, there is little evidence to suggest that wild cheetah
VetBooks.ir populations have reduced immune competence.

FIG. 11.12 An example of how MHC polymorphism can generate
an enormous number of different MHC haplotypes. The numbers
above each locus are the number of identified alleles in the human
MHC. The number of different combinations can be determined by
9
multiplying all of them together. Thus there are 13 × 10 class II
7
18
combinations, 12 × 10 class I combinations, and 1.7 × 10 total
possible combinations; more than sufficient to give every human a
unique haplotype.

There are many examples of links between MHC haplotype and
resistance to infectious disease. For example, in cattle there is an
association between possession of certain BoLA alleles and
resistance to bovine leukosis, squamous cell eye carcinoma, and
trypanosomiasis; responsiveness to foot-and-mouth disease virus;

and susceptibility to the tick Boophilus microplus. In sheep, there is
an association of the class I allele SY1 with resistance to
Trichostrongylus colubriformis. Resistance to scrapie and caseous

lymphadenitis is also associated with certain MHC class I alleles. In
goats, the class I allele Be7 is associated with resistance, and Be1
and Be14 are associated with susceptibility, to caprine arthritis-
encephalitis. In horses, an allergic response to the bites of Culicoides
midges is linked to ELA-Aw7. In pigs, the SLA complex has an

influence on major reproduction parameters such as ovulation rate,
litter size, and piglet viability.
Selection for specific MHC haplotypes has potential for use in
developing disease-resistant strains of domestic animals. However,

it must be pointed out that by selecting for a specific gene locus, one
may also inadvertently select for susceptibility at closely linked loci.
This may outweigh the benefits of a resistant allele at one locus. An
animal cannot be resistant to all possible infectious diseases.

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