Phagocytic function of human blood polymorphonuclear leukocytes in the presence of carrageenan, a potential vaginal microbicide.

Carrageenan is currently undergoing clinical trials as the active constituent of a vaginal gel product for use as a female-controlled option to prevent the transmission of HIV during sexual intercourse. Here we show that in the presence of 0.5 mg/ml of carrageenan, human blood polymorphonuclear leukocytes (PMN) do not ingest this material, as evidenced by a lack of progressive vacuolization, but can ingest microorganisms present in the medium, excluding adjacent carrageenan. Moreover, PMN move at normal speeds, respond chemotactically, and reduce nitroblue tetrazolium (NBT) to formazan on stimulation. Hence, in the presence of carrageenan the phagocytic response appears to remain intact.