A comparison of IgA in portal and peripheral venous blood.

A comparison of IgA in portal and peripheral venous blood was made to elucidate further any possible role of the liver in IgA functions in man. Over fifty paired samples of portal and peripheral blood were obtained from patients undergoing abdominal surgery. The samples were examined for total IgA and secretory IgA content, IgA immune complexes, and the proportion of polymeric IgA and IgA antibodies to Streptococcus mutans and Escherichia coli. No significant differences in the overall IgA concentration in portal and peripheral venous blood were found, but the concentration of secretory IgA was raised in portal blood (P less than 0.02). The IgA content of immune complexes (PEG precipitates) was significantly raised in portal sera compared with peripheral sera. Antibody levels to S. mutans or E. coli were not significantly different in the paired samples. A mean of 18.1% of the IgA in portal blood was greater than 7S in size compared with a mean of 15.3% in peripheral blood (P less than 0.01). Detectable differences between IgA in portal and peripheral venous blood could indicate some role of the liver in the transport of polymeric IgA and IgA complexes from serum to bile in man, but could represent increased production of these types of IgA in tissues drained by the portal vein.