A sensitive blotting system for detection of alpha-fetoprotein variants with monoclonal and polyclonal antibodies

Human alpha-fetoprotein (AFP) variants from cord sera were separated by isoelectric focusing in agarose gels under native conditions, transferred to nitrocellulose paper and detected with polyclonal and monoclonal antibodies (Moabs). Rabbit anti-AFP recognized up to 9 individual electrophoretic variants in the range of pH 4.5 to pH 5.2. The reactivity of 8 Moabs ranged from weak to strong and showed variability in the pattern of AFP bands recognized. Moabs were separated into 3 groups according to the number of bands detected: group 1 detected 6 to 7 bands; group 2 recognized only one band; and group 3 recognized 4 bands. The sensitivity of the system with polyclonal antibodies was 0.15 ng of AFP in complete cord serum and varied between 300 and 0.2 ng with Moabs.