Surface binding and catabolism of low-density lipoprotein by circulating lymphocytes from patients with abetalipoproteinaemia, with observations on sterol synthesis in lymphocytes from one patient.

Surface binding of low-density lipoprotein (LDL), degradation of LDL protein and sterol synthesis were investigated in freshly isolated lymphocytes from normal and abetalipoproteinamic human subjects. LDL binding as a function of LDL concentration showed no evidence of the presence of high-affinity binding sites in fresh lymphocytes from either group of subjects. The rate of degradation of LDL protein by lymphocytes from the patients was no greater than that from the normal subjects and, in the fresh lymphocytes of the one patient studied, sterol synthesis was not increased. We conclude that the formation of LDL receptors and the synthesis of sterol in circulating lymphocytes are largely suppressed and that in normal subjects this may be due to the presence of some plasma constituent other than LDL, possibly the apoE protein. This conclusion is discussed in relation to the possible contribution of LDL receptors to the degradation of LDL protein in vivo.