Studies of Lp-lipoprotein as a quantitative genetic trait.

Sera from 11 individuals which were classified as Lp(a-) by direct gel diffusion and by absorption tests showed the presence of Lp(a) lipoprotein when the sera were concentrated 120-fold. This Lp(a) antigen was demonstrated by gel diffusion to be indistinguishable from Lp-lipoprotein isolated from known Lp(a+) sera. The Lp(a) preparations from sera classified Lp(a-) also showed electrophoretic mobility in immunoelectrophoresis and schlieren diagrams in ultracentrifugal analyses similar to Lp-lipoprotein from Lp(a+) sera. The proposal is made that observed individual variations in tests for the Lp-lipoprotein reflect a quantitative genetic trait and that it is likely that different individuals produce Lp-lipoprotein in widely varying amounts. The consistency of this proposal with certain previous observations on the Lp system is discussed.