Serum alpha-fetoprotein subfractions in pregnant women identified by the modified method of lectin affinity crossed-line immunoelectrophoresis.

Using a modified method of lectin affinity crossed-line immunoelectrophoresis, we studied the alpha-fetoprotein (AFP) subfractions in sera from 12 pregnant Japanese women, at 22 and 42 weeks of gestation. The method involves the first dimension electrophoresis in agarose gel containing concanavalin A (Con A) or lentil lectin (LCH), the second dimension immunoelectrophoresis in agarose gel containing polyclonal antibody against AFP, reaction with peroxidase-conjugated Protein A and staining with 4-methoxy-1-naphthol. We found that type a of Con A or type C of LCH was the only subfraction present in maternal circulation at the second or third trimester. These AFP subfractions were assumed to be of fetal liver-origin. The minimum concentration which yielded an immunoprecipitation peak was approximately 100 ng/ml, being twenty times more sensitive than the conventional lectin affinity crossed-line immunoelectrophoresis.