The techniques of agar immunoelectrophoresis and agar double diffusion were applied to the study of the antigenicity of ß- and α1-lipoproteins separated by ultracentrifugation from normal human sera. The effects of delipidation were also investigated.
It was shown that ß- and α1-lipoproteins are antigenically distinct. For each class of lipoprotein studied, a single antigenic component was demonstrated. In some, but not all, preparations of α1-lipoprotein a second, small antigenic component was detected, and identified as albumin. Absorption with lipoprotein-free serum or albumin removed this component without changing the lipoprotein band.
Delipidation did not affect the antigenicity of either ß- or α1-lipoproteins. Immunoelectrophoresis, because of its high sensitivity and specificity, provides an additional criterion of purity for antigenic proteins in addition to the data that can be obtained from ultracentrifugal and free electrophoretic analysis.