Apolipoprotein E phenotyping from serum by Western blotting

Abstract A new method for the apolipoprotein E (apo E) phenotyping directly from human serum has been developed. The method is based on isoelectric focusing of delipidated serum in vertical slab gel systems followed by blotting and immunostaining using polyclonal anti‐apo E antibodies as the first antibody. Apo E phenotyping with this method in 150 serum samples gave exactly the same results as obtained with the conventional method based on isoelectric focusing of delipidated very low density lipoproteins isolated by ultracentrifugation and detected by protein staining. Compared with the conventional method, the present method is less expensive, suitable for large‐scale screening purposes e. g. diagnosis of type III hyperlipidemia and needs only a few microliters of serum. By application for screening of hyperlipidemic sera, we were able to detect two patients with an apo E‐1 variant and two others with “new” E‐3 and E‐4 mutants by the described methods. In addition apparent molecular weight variants of apo E could be detected by sodium dodecyl sulfate‐gel electrophoresis of sera followed by blotting and immunostaining.