Diethylcarbamazine dependent, complement mediated, adherence and cytotoxicity of cells on microfilariae of Litomosoides carinii.

Diethylcarbamazine (DEC) induced dose dependent adherence of normal spleen cells from Mastomys natalensis to microfilariae of L. carinii in the presence of serum from Mastomys infected with L. carinii or normal serum. The effect could be also induced, using fresh, normal human serum and human blood leucocytes. The responsible serum factor was heat labile (56 degrees C, 30 min) and was eliminated from the sera by pretreatment with Inulin. The activity could be reconstituted by normal serum. Cell adhesion was inhibited by 0.004 MEDTA while 0.004 M EGTA had only a weak inhibitory effect. The addition of Mg++ led to high adherence rates in the presence of EGTA. The data indicate that DEC activates complement on the surface of the larval sheath by the alternate pathway. Adherent Mastomys cells or human cells had a cytotoxic effect on the larvae. The death of the microfilariae did not depend on the loss of the larval sheath.