title: Putting J chain back on the map: how might its expression define plasma cell development?
abstract: Joining chain (J chain) is a small polypeptide that regulates multimerization of secretory IgM and IgA, the only two mammalian Igs capable of forming multimers. J chain also is required for poly-Ig receptor-mediated transport of these Ig classes across the mucosal epithelium. It is generally assumed that all plasma cells express J chain regardless of expressed isotype, despite the documented presence of J chain(-) plasma cells in mammals, specifically in all monomeric IgA-secreting cells and some IgG-secreting cells. Compared with most other immune molecules, J chain has not been studied extensively, in part because of technical limitations. Even the reported phenotype of the J chain-knockout mouse is often misunderstood or underappreciated. In this short review, we discuss J chain in light of the various proposed models of its expression and regulation, with an added focus on its evolutionary significance, as well as its expression in different B cell lineages/differentiation states.
authors.affiliation: Department of Microbiology and Immunology, University of Maryland, Baltimore, MD 21201.
authors.forename: Caitlin D
authors.initials: CD
authors.lastname: Castro
authors.affiliation: Department of Microbiology and Immunology, University of Maryland, Baltimore, MD 21201 MFlajnik@som.umaryland.edu.
authors.forename: Martin F
authors.initials: MF
authors.lastname: Flajnik
mesh_terms: D000818:Animals; D005786:Gene Expression Regulation / Q000276:immunology*; D006801:Humans; D007070:Immunoglobulin A / Q000276:immunology*; D007144:Immunoglobulin J-Chains / Q000276:immunology*; D007075:Immunoglobulin M / Q000276:immunology*; D051379:Mice; D010950:Plasma Cells / Q000166:cytology / Q000276:immunology*; D021381:Protein Transport / Q000276:immunology; D019056:Receptors, Polymeric Immunoglobulin / Q000276:immunology*
chemical_list: D007070:Immunoglobulin A; D007144:Immunoglobulin J-Chains; D007075:Immunoglobulin M; D019056:Receptors, Polymeric Immunoglobulin