An antibodylike paraprotein has been isolated from a patient with multiple myeloma and autoimmune hyperlipoproteinemia.The paraprotein bound to apolipoprotein B (apo B)-containing lipoproteins that formed macromolecular aggregates, and globules thought to be aggregated complexes of lipoproteins and reactive immunoglobulins were observed circulating within the retinal blood vessels of this patient. This binding specificity permitted purification of the paraprotein from both the agglutinated immune complexes and from the plasma.The protein is an IgA, K-immunoglobulin which exists primarily in a polymeric state. Capillary immunoprecipitation demonstrated reactivity with very low density lipoproteins (VLDL) and low density proteins (LDL), but not with high density lipoproteins (HDL). Delipidated apo B and apo E, but not apo A or apo C, formed precipitates with this immunoglobulin. In using a radioimmunoassay format, the affinity of the immunoglobulin was greatest for VLDL
Vol. 74, No. 11, pp. 5150-5154, November 1977 Medical Sciences Solubilization of apolipoprotein B and its specific binding by the cellular receptor for low density lipoprotein Communicated by Frederic M. Richards, August 10, 1977 ABSTRACT Low density lipoprotein (LDL) and very low density lipoprotein (VLDL) ind specifically to a receptor on fibroblasts, and it has been postulated that the apoprotein of LDL (apo B) confers the specificity of cellular binding. This hypothesis has been testedrin the present study with a water-
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