In the process of antibody response, after the antigen activates the B cell, the Ig category expressed and secreted on the membrane will be converted from IgM to IgG, IgA, IgE and other categories or subclasses of Ig, also known as allotype conversion. At this time, the Ig variable region remains unchanged, that is, the specificity of the binding antigen is the same, but its heavy chain type (constant region) changes.
