Joining chain of multimeric IgA and IgM (J chain (JCHAIN))

The **joining chain of multimeric IgA and IgM** (J chain, JCHAIN) is a small, acidic polypeptide uniquely involved in **regulating the assembly and secretion of polymeric immunoglobulins IgA and IgM** in mammals[1][2][3]. It is encoded by the IGJ gene and is incorporated into IgA and IgM molecules through disulfide bonds, allowing IgA to form dimers and IgM to form pentamers rather than hexamers[1][2][3]. The presence of the J chain is required for these polymeric immunoglobulins to bind the polymeric Ig receptor (pIgR), enabling their transcytosis across mucosal epithelia into secretions[1][2]. The J chain's function is specific to IgA and IgM, with no direct roles in other immunoglobulin classes. While it is critical for mucosal immune defense and immune complex formation, there are currently no drugs known to directly target the J chain, and there are no established safety concerns, biomarker applications, or direct therapeutic indications relevant to therapeutic targeting of this molecule[1][2][3][4].

Other names

Immunoglobulin J chainIGJIGCJJCHIgJ chainimmunoglobulin J polypeptidelinker protein for immunoglobulin alpha and mu polypeptides