Demonstration of serum protein differences in cystic fibrosis by isoelectric focusing in thin-layer polyacrylamide gels

Abstract

Whole serum samples from cystic fibrosis patients, heterozygotes and normal individuals were analyzed using isoelectric focusing in thin-layer polyacrylamide gels. Using this technique consistent serum protein differences between the three serum types have been demonstrated. A protein with an isoelectric point of 5.48 ± 0.1 was found in 14 out of 17 normal sera and in all heterozygote sera tested but not in 15 out of 16 cystic fibrosis sera tested. A protein with an isoelectric point of 8.41 ± 0.1 was found in 12 out of 13 cystic fibrosis sera and all heterozygote sera but not in 11 out of 12 normal sera tested. The concentration of both of these proteins was demonstrated to be variable among the heterozygotes as shown by electrofocusing of different volumes of serum. Partial characterization of both proteins was achieved using the combined techniques of isoelectric focusing, immunoelectrophoresis, acrylamide to ionagar electrophoresis, ammonium sulfate precipitation and diethylaminoethylcellulose chromatography (pH 8.0). The protein with an isoelectric point at pH 5.48 ± 0.1 was found to be a heat labile beta-globulin and the protein with an isoelectric point of 8.41 ± 0.1 was found to be a heat labile gamma-globulin. The significance of the findings are discussed.