Analysis of alpha-fetoprotein by a procedure combining crossed immunoaffinoelectrophoresis and immunoblotting

A newly developed procedure combining crossed immunoaffinoelectrophoresis and an immunoblotting assay (CIAE-IBA) has been used to discriminate between and precisely quantitate lectin-bound and lectin-free forms of alpha-fetoprotein (AFP) derived from human serum at levels of AFP as low as 5.6 ng/ml (adult reference range, 0 to 15). Twenty-two serum specimens with elevated levels of AFP were examined by a reference CIAE method, using either of two lectins, concanavalin A (Con A) or Lens culinaris agglutinin (LCA); aliquots of the specimens were then diluted in AFP-free serum to normal or near-normal levels of AFP and examined by CIAE-IBA, which included a final protein transfer to nitrocellulose. The quantitative results produced by the two methods were essentially the same. Overall, the sensitivity of the CIAE-IBA procedure surpasses that of other CIAE methods of AFP fractionation. The CIAE-IBA procedure may be used for study of the heterogeneity of AFP and may be applicable as well to the study of other proteins.