Antigen-binding cells in human fetal liver.

Antigen-binding cells (ABC) could be detected regularly by autoradiography among haemic cells in the liver of human fetuses ranging in age from 8 to 24 weeks. For radioiodine-labeled thyroglobulin, the antigen mainly used in these studies, counts of ABC ranged from 5.0 to 24.3 per 1,000 cells scanned. There was a trend for counts of ABC in liver to be highest at 10-12 weeks of fetal life. Binding of labeled thyroglobulin was inhibited by excess unlabeled thyroglobulin, but not by other protein antigens. Artifacts due to binding of antigen to normoblasts, which comprised 90% of the haemic cells in fetal lines, and to cells with 'sticky' surfaces were excluded as far as possible. There was no response by fetal liver cells to phytohaemagglutinin. Although there was only minimal inhibition of binding by anti-immunoglobulin sera of known potency, the ABC in human fetal liver were assumed to correspond to immunoglobulin-bearing precursors of B cells described by others in the liver of the fetal mouse.