Final answer:
The variable regions of immune receptors provide antigen specificity due to their diverse genetic rearrangement, while the constant regions afford stability and define antibody classes.
Step-by-step explanation:
The variable regions of the T cell receptor and the B cell receptor contribute to antigen specificity, and the constant regions make up the more conservative flanking regions.
The variable regions, including the V, D, and J gene segments, undergo genetic recombination to produce a vast diversity in antigen-binding sites, allowing the immune system to recognize a multitude of different antigens.
In contrast, the constant regions are more stable and exhibit less variation, providing structural consistency and defining the class of the antibody.