Which two antibodies are known to contain J chains?

The correct answer, which identifies the antibodies that contain J chains, highlights a key aspect of immunoglobulin structure and function. J chains, or joining chains, are polypeptides that play a crucial role in the assembly of multimeric antibodies.

In the case of IgA, which is often found in secretions like saliva, tears, and breast milk, the J chain facilitates the formation of secretory IgA dimers. These dimers are vital for mucosal immunity, allowing for the effective transport of antibodies across mucosal surfaces to provide localized protection against pathogens.

IgM, on the other hand, is a pentameric antibody, meaning it consists of five monomer units linked together. The J chain is essential for the stability and assembly of this structure, enabling IgM to effectively activate the complement system and provide a robust immune response during the initial stages of infection.

In contrast, antibodies like IgG and IgE do not contain J chains. IgG is predominantly found in serum and is a monomer, while IgE, involved in allergic responses and protection against parasitic infections, exists as a monomer as well.

Understanding the role of J chains in IgA and IgM underscores the importance of these antibodies in both