Some years ago, a series of human serum lipoproteins, distinguishable by their hydrated densities and lipid-protein ratios were recognized and isolated by ultracentrifugal techniques (1). Certain of these lipoproteins are invariably present in human serum and the concentrations of these and of others can be quantitatively correlated with disease (2). No difference in the lipoprotein distribution can be demonstrated between serum and plasma. The purpose of this investigation was to obtain information about the immunochemical specificity of some of the lipoproteins
