Action of Micrurus spp venoms on the complement pathways. Samples (50 μl) of normal human serum (NHS), as complement source, were incubated with 50 μl of Micrurus spp venoms (50 μg) or PBS for 30 min at 37°C. The residual complement lytic activity of the mixtures was measured using antibody-sensitized sheep erythrocytes, as targets, for classical pathway [A]. After incubation for 1 h at 37°C, the absorbance of the supernatants was measured at λ414 nm and the percentage of haemolysis calculated. The residual lectin pathway complement activity [B] was determined on ELISA plates coated with mannan. Data are representative for three separate experiments and expressed as mean of duplicates +/-SD. Results were expressed as reduction of percentage of haemolysis [for A] or reduction of C4 binding [B] in relation to the control samples (NHS + buffer).