AN ISOANTIGENIC LIPOPROTEIN 



75 



ether wash. Between 20 and 40 per cent of the weight of the 

 particulate fraction is recovered from the Triton extract. 



(C) Fractionation of the acetone-precipitated material by extraction 

 with aqueous salt solutions. Three extractions with o* iM-phosphate 

 buffer pH 7-2 and three extractions with 0-14 M-NaCl dissolve 

 approximately 85 per cent of the material. Only small amounts of 



B 



0.5 



1.0 2.0 



mg 



4.0 



Fig. 2. Inhibition of the hacmagglutinating activity of two isoantisera, 

 C57BL/10 anti-Bio.D2 (A) and (C57BL/6X DBA/2)Fi anti-CsH (B), 

 by increasing quantities of the different fractions. Blood cells used in the 

 assay were collected from A/Sn mice. Cells for negative control tests 

 were from strain B10.D2. 



Particulate fraction X X 



Whole Triton extract • • 



Triton-soluble lipoprotein (TSL) ▲ A 



Water-soluble fraction ■ ■ 



protein are obtained in further extracts. The fraction poorly 

 soluble in water appears to be an electrophoretically homogeneous 

 lipoprotein and is hereafter referred to as Triton-soluble lipo- 

 protein (TSL). Antigenic activities of the Triton extract and of 

 subfractions obtained by differential extraction are compared 

 in Table I, and their relative abilities to inhibit haemagglutination 

 are illustrated in Fig. 2. 



