Final answer:
Isotype switching is the recombination within constant region gene segments, enabling B cells to produce different classes of antibodies with unchanged epitope specificity.
Step-by-step explanation:
Isotype switching is accomplished by recombination within a cluster of constant region gene segments in plasma cells. This process, known as class switching or isotype switching, involves the rearrangement of gene segments encoding the constant region of antibodies, which determines the class of the antibody (IgG, IgA, or IgE) produced by plasma cells. While the constant region changes, the variable region, responsible for epitope specificity, remains the same. This mechanism enables a single clone of B cells to produce different classes of antibodies, all with the same specificity for the antigen they were originally activated against.