Comparison between natural and immunized anti-GM1 antibodies analyzed by marker releasing rate assay with liposome

Naturally occurring rabbit anti-GM1 was compared with immunized induced anti-GM1 antibody in the same individual rabbits by the characterization of immune potency determined by complement-dependent damage to liposomes containing GM1 as antigen. Antigen-antibody reaction was the rate determining step in this assay. The maximum rate was measured by the first derivative conversion monitoring in spectrophotometry and the maximum level of marker released was measured by the conventional method described previously. When the concentration of sera required to get fifty percent of maximum values in each assay were compared, the ratios (rate assay/conventional assay) were 5.7 to 10.0 in natural antibodies and 3.2 to 2.3 in immunized induced antibodies, respectively. Furthermore, the maximum rate of marker release from liposome was not correlated with the maximum level of marker released depended on the sources of antibodies. These results suggest that natural antibody, even the titer was high in conventional liposome assay, has different characteristics compared with the immunized induced antibody.