Enhanced complement-mediated killing of T. spiralis NBL incubated with mAb 9G3. NBL were pretreated with different volumes (2 μl, 20 μl and 40 μl) of mAb 9G3 (1 mg/ml), the irrelevant mAb 7E2 (1 mg/ml) or normal mouse serum prior to the addition of 100 μl of normal human serum. Heat-inactivated human serum served as a control. The mortality of the NBL was assessed under an inverted microscope. The results are presented as the arithmetic mean ± standard error (SE) from triplicate experiments. **p < 0.01, *p < 0.05 compared with the normal mouse sera control.