Mechanism of destruction of Brugia malayi microfilariae in vitro: the role of antibody and leucocytes.

Human and monkey leucocytes in serum from previously patent Brugia malayi infected monkeys adhered to and caused cytotoxicity to microfilariae of B. malayi in vitro. The phenomenon also occurred in human serum from confirmed cases of bancroftian and malayan elephantiasis. Adherence of leucocytes was not seen in serum from uninfected monkeys, monkeys with patent B. malayi infection and serum from rats infected with Breinlia booliati but now amicrofilaraemic. Immune serum failed to promote adherence of leucocytes to L3 of B. malayi. The activity was lost when the serum was either incubated with Protein A-bearing Staphylococcus aureus or heat inactivated at 56 degrees C for 30 min. Light and electron microscopic observations regarding the type of adhering cells and sequence of events following adherence are described.