Quantitative Study of the Uptake of IgA by Isolated Rat Hepatocytes

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Abstract
Recently dispersed rat hepatocytes showed high capacity for uptake of monomers and polymeric human IgA by simple adsorptive endocytosis. Maximum uptake exceeded 15 million monomer units pit cell. The asialo‐glycoprotein receptor was not involved in this process. J chain‐containing polymers were on the average taken up somewhat better than monomers and substantially better than J chain‐deficient polymers. This result would agree with a partial involvement of the secretory component (SC) in the adsorptive uptake of IgA. Different receptor mechanisms might hence explain the hepatic transport of IgA from blood to bile in the rat and perhaps he involved in the catabolism of IgA. After binding lo the plasma membrane of the rat hepatocyte, most of the human IgA was internalized in endocytic vesicles. A considerable proportion of radiolabelled IgA apparently reached the lysosomes after internalization became degraded.