[Study of the nature and mechanism of action of virus neutralizing inhibitors of the blood].

Low-density lipoproteins (LDL, d 1.0.40-1.053 g/ml) and high-density lipoproteins (subfraction 3 of HDL, d 1.210 g/ml) were isolated by preparative ultracentrifugation at the NaBr density gradient. The findings have led to the conclusion that LDL or beta-LP are not thermolabile, but they represent a thermoresistant serum virus-inhibiting factor. At the same time HDL3 has pronounced thermolabile properties. The mechanisms of action of the above factors are explained in the paper.