The isotype of monoclonal antibodies is essential for sequencing or purification of antibody from cell culture supernatant. Additionally, the specific isotype can play a role in the therapeutic development of an antibody as the constant region plays a crucial role through interaction of the mAb Fc with receptors on immune cells.
(Stephen A. Beers, Martin J. Glennie, and Ann L. White. Influence of immunoglobulin isotype on therapeutic antibody function. Blood. 2016 Mar 3; 127(9): 1097–1101. PMID: 26764357)