A common feature of many autoimmune disorders is the development of autoreactive antibodies. The constant domain, which designates the antibody isotype and subclass, determines the effector activities of (auto) antibodies. IgG is the most common isotype seen in serum and is frequently the only isotype utilized in diagnostic tests. Autoantibody reactions can each have a distinct isotype/subclass profile. For a study, researchers sought to describe the isotype/subclass profiles of the most well-known autoantibodies since comparing autoantibody isotype patterns may provide fresh perspectives on the pathophysiology of the illness. 

The first-of-its-kind analysis revealed that autoantibodies have unique isotype patterns across many illnesses, despite significant diversity between (and within) autoantibody responses. IgG (and particularly IgG1) predominates in most autoantibody reactions; an IgG4 predominance marks many specific disorders. IgE is important in various disorders. Significant characteristics of autoantibody isotype/subclass profiles are observed in clinically unrelated disorders, indicating possible overlapping pathways in response evolution, disease etiology, and treatment response. 

They knew very little about isotypes other than IgG in many autoantibody reactions, which left significant gaps in the knowledge of the pathophysiology of autoimmune disorders. 

Future studies should go into greater depth on isotype/subclass profiling and include autoantibody parameters other than total IgG in illness models and clinical investigations.

Reference: jacionline.org/article/S0091-6749(22)00845-4/fulltext