We have created J chain knockout mice to define the physiologic role of the J chain in immunoglobulin synthesis and transport. The J chain is covalently associated with pentameric immunoglobulin (Ig) M and dimeric IgA and is also expressed in most IgG-secreting cells. J chain-deficient mice have normal serum IgM and IgG levels but markedly elevated serum IgA. Although polymeric IgA was present in the mutant mice, a larger proportion of their serum IgA was monomeric than was found in wild-type mouse serum. Bile and fecal IgA levels were decreased in J chain-deficient mice compared with wild-type mice, suggesting inefficient transport of J chain-deficient IgA by hepatic polymeric immunoglobulin receptors (pIgR). The pIgR-mediated transport of serum-derived IgA from wild-type and mutant mice was assessed in Madin-Darby canine kidney (MDCK) cells transfected with the pIgR. These studies revealed selective transport by pIgR-expressing MDCK cells of wild-type IgA but not J chain-deficient IgA. We conclude that although the J chain is not required for IgA dimerization, it does affect the efficiency of polymerization or have a role in maintaining IgA dimer stability. Furthermore, the J chain is essential for efficient hepatic pIgR transport of IgA.
Altered hepatic transport of immunoglobulin A in mice lacking the J chain.
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B A Hendrickson, D A Conner, D J Ladd, D Kendall, J E Casanova, B Corthesy, E E Max, M R Neutra, C E Seidman, J G Seidman; Altered hepatic transport of immunoglobulin A in mice lacking the J chain.. J Exp Med 1 December 1995; 182 (6): 1905–1911. doi: https://doi.org/10.1084/jem.182.6.1905
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