Page 302 - Veterinary Immunology, 10th Edition

VetBooks.ir After reading this chapter, you should be able to:

• Describe the differences between the structure and functions of the major
histocompatibility complex (MHC) class I and class II molecules.
• Explain MHC polymorphism and its significance in binding exogenous and

endogenous antigens.
• Explain the different functions of polymorphic and nonpolymorphic MHC
molecules.

• Understand the mechanisms involved and the reasons behind the maintenance
of MHC polymorphism.
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• Describe how MHC class I molecules present endogenous antigens to CD8 T
cells.
+
• Describe how MHC class II molecules present exogenous antigens to CD4 T
cells.
• Describe the contents of the class III region of the MHC.
• Describe the structural basis of MHC-antigen binding.
• Define major histocompatibility complex, exogenous and endogenous antigens,

MHC polymorphism, and haplotype.
• Describe the role of the MHC in odor recognition.

• Explain the relationship between MHC haplotype and disease susceptibility.
• Understand the two strategies mammals use to generate MHC polymorphism;
allelic polymorphisms, and variations in gene content.

Resistance to infectious diseases is one of the most strongly

inherited disease traits. After all, a lethal infection effectively
removes susceptible individuals from the gene pool. “Survival of
the fittest” applies most strongly to individuals required to defend
themselves against infectious agents. As a result, many genes can

influence resistance to infection. The most important of these genes
are those encoding cell surface glycoproteins that constitute the
major histocompatibility complex (MHC).
In order to trigger adaptive immunity, antigen molecules must

first be processed. They are broken up inside cells, and the
fragments generated are bound to appropriate antigen-presenting
receptors (Fig. 11.1). These antigen-presenting receptors are cell
surface glycoproteins encoded by genes clustered together to form

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