Immunofluorescence studies of apolipoprotein B in intestinal mucosa

During fat absorption, active synthesis of cholesterol, phospholipids, and specific apolipoproteins are required for chylomicron formation and secretion. In the inherited disease abetalipoproteinema, chylomicrons cannot be made in response to fat feeding, and they as well as low and very low density lipoproteins are completely absent from plasma. The genetic defect in the disease is presumed to be an inability to synthesize apolipoprotein B, the apoprotein common to all the above lipoprotein classes, but such a defect has not been directly demonstrated. With peroral intestinal biopsies and immunofluorescence techniques, we have demonstrated the presence and intracellular localization of apolipoprotein B within jejunal epithelial cells of five normal subjects and have shown that its content increases markedly after fat feeding. In two patients with abetalipoproteinemia no apolipoprotein B was seen by immunofluorescence techniques in the jejunal mucosa in the fasting state or after a fatty meal. Intestinal synthesis of apolipoprotein B appears not to occur in abetalipoproteinemia.