Page 512 - Veterinary Immunology, 10th Edition

VetBooks.ir Antigen Receptor Genes

The information needed to make all proteins, including antigen
receptors, is stored in an animal's genome. All that is required for

the production of these molecules is that the necessary genes be
turned on. Once the appropriate genes are activated, they can be
transcribed into RNA and translated into the appropriate receptor
protein on B or T cells. It has been estimated that mammals can
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produce up to 10 different antigen receptors to be expressed on B
and T cells. In order to produce this enormous diversity, they use
fewer than 500 genes!
Multiple genes code for each receptor peptide chain. Several

genes code for each variable region, whereas only one codes for a
constant region. As a result, the single constant-region gene can be
combined with any one of several variable-region genes to make a
complete receptor chain (Fig. 17.2). Instead of having genes for all
possible receptor chains, it is only necessary to have genes for all

the variable regions and to join these to an appropriate constant-
region gene as required. In addition, antigen receptor chains may
be paired in different combinations to yield even greater diversity, a

process called combinatorial association.

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