CHARACTERIZATION OF ANTIGANGLIOSIDE ANTIBODIES PRESENT IN NORMAL HUMAN PLASMA

Samples of plasma from normal human adults were screened for anti-ganglioside antibodies by HPTLC-immunostaining and enzyme-linked immunosorbent assay (ELISA). All the samples analyzed showed IgM-immunoreactivity to GM(1) ganglioside and its related glycolipid GA(1). Reactivity to GD(1b), GM(2) and LM(1) was also detected in 85, 80 and 20% of the analyzed samples, respectively. The main immunoreactivity is related to the asialo-ganglioside GA(1). Using inhibition by soluble antigen and affinity chromatography techniques it was possible to distinguish two populations of anti-GA(1) antibodies. One with high affinity reacting only with GA(1), and another with low affinity reacting also with GM(1) and GD(1b). The antibodies that recognize GM(2) are of low affinity and appear to be different from those that react with GA(1). We postulate that the anti-GM(1)/GD(1b) immunoreactivity present in normal human plasma could be a cross-reaction of antibodies originally directed to a GA(1)-like carbohydrate structure. Anti-GA(1) and anti-GM(1) titers were calculated as the reciprocal of the plasma dilution needed to obtain the half maximal antibody binding, a titer definition that we consider more suitable to compare data from different laboratories than those usually employed.