Antibody production by human colostral cells. I. Immunoglobulin class, specificity, and quantity.

The production of antibody by human colostral cells was assayed by the hemolysis in-gel technique. When sheep erythrocytes coated with O antigens from frequently encountered Escherichia coli bacteria were used as detector cells and anti-IgA serum was added for development, numerous plaque-forming cells (PFC) were demonstrated in all samples tested. In contrast, plaques were rarely seen in the presence of anti-IgG developing serum. The direct (IgM) plaques occasionally noted with both antigen-coated and uncoated sheep erythrocytes were mainly due to the production of heterophil antibodies, since they were not formed when human erythrocytes were used as O-antigen carriers. A strikingly high number of the colostral lymphocytes formed antibodies to the E. coli antigens, up to 8%. This suggests that these cells represent a rather selective population--possibly cells from the gastrointestinal tract exposed to enteric bacteria. The large number of plaques observed, the predominance of the cells forming IgA antibodies, and the marked changes in PFC number in relationship to parturition pose a number of questions relevant to the antibody-producing colostrum cells and their relationship to the secretory immune system.