[Radiochemical and immunohistochemical determination of surface binding of low density lipoproteins on lymphocytes]

Human peripheral blood lymphocytes bind and take up low density lipoprotein (LDL) by receptor-mediated endocytosis. The binding of LDL was determined by incubation with 125-I-LDL and an immunohistochemical assay. By both techniques a diminished rate of binding was found when cells were freshly isolated from the blood, but increased five- to ten-fold when lymphocytes were incubated in lipoprotein-deficient medium for 72 hours. In addition, it was shown immunohistochemically that only few cells showed an LDL-dependent fluorescent labelling: approximately 5 to 10 per cent of the freshly isolated lymphocytes and 40 to 50 per cent of the cells incubated for 72 hours under lipoprotein-free conditions. The present data indicate that not only the high affinity LDL-receptor described by Goldstein and Braun may be involved in the uptake of cholesterol by lymphocytes, but also other binding-sites, which may have immunological function in some lymphocyte subpopulations.