Immunoglobulin class switching, also known as
isotype switching,
isotypic commutation or
class-switch recombination (CSR), is a biological mechanism that changes a
B cell's production of
immunoglobulin (
antibodies) from one type to another, such as from the
isotype IgM to the isotype
IgG. During this process, the constant-region portion of the antibody
heavy chain is changed, but the variable region of the heavy chain stays the same (the terms "variable" and "constant" refer to changes or lack thereof between antibodies that target different
epitopes). Since the variable region does not change, class switching does not affect antigen specificity. Instead, the antibody retains
affinity for the same antigens, but can interact with different
effector molecules.