The potential of human secretory IgA to act as an opsonin for Staphylococcus aureus was tested in an in vitro phagocytosis assay system. Secretory IgA, isolated separately from each of nine mothers and containing agglutinating antibodies against the Staphylococcus used in test, did not have opsonic effect in concentrations between 20 and 100 mg/100 ml. The addition of lysozyme and serum to the test mixture did not affect the results. Whole colostrum potentiated growth of the organisms in the in vitro assay system, suggesting that IgA is not dependent upon other substances present in secretions for opsonic effect. No inhibition or potentiation by secretory IgA of an established opsonic reaction could be demonstrated. These data support the concept that secretory IgA has little, if any, capacity to act as an opsonin for polymorphonuclear leukocytes.
No takes yet. Share an insight, caveat, or question.
I. Dodd Wilson (1972) studied this question.