The J-chain is associated with which immunoglobulin?

The J-chain is a polypeptide that plays a crucial role in the structure and function of certain immunoglobulins, specifically IgA and IgM. Its primary function is to facilitate the formation of polymeric immunoglobulins, allowing these antibodies to exist as dimers or pentamers.

In the context of IgA, the J-chain enables the aggregation of two IgA monomers to form the secretory form of IgA, which is important for mucosal immunity in areas such as the gastrointestinal and respiratory tracts. This is particularly relevant in providing immune protection at mucosal surfaces where pathogens are often encountered.

While IgM also contains a J-chain, the question specifically relates to the association of the J-chain with immunoglobulin types. Since IgA primarily circulates as a dimer in secretions and has a well-documented reliance on the J-chain for its function, it highlights the importance of this molecule in mediating immune responses at mucosal surfaces.