LYMPHOCYTE-ACTIVATING FACTOR .1. GENERATION AND PHYSICOCHEMICAL CHARACTERIZATION

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  • 1 January 1978
    • journal article
    • research article
    • Vol. 121  (4) , 1446-1452
Abstract
Lipopolysaccharide[Escherichia coli]-activated murine peritoneal macrophages elaborate lymphocyte-activating factor (LAF) which is mitogenic for murine thymocytes. A method of LAF production was presented that permits the generation of a relatively homogeneous molecular species. LAF had an isoelectric point of 4.8 (range 4.7-4.9). The MW was determined by using several physical techniques. The apparent sedimentation coefficient (S20,w) was 2.0S by sucrose gradient ultracentrifugation. The Stokes (molecular) radius determined by gel filtration on Sephadex G-75 was 22 .ANG. (range 21.5-22.5); the calculated diffusion coefficient (D20,w) was 9.7 .times. 10-7 cm2/s (range 9.5 .times. 10-7 to 9.9 .times. 10-7). The buoyant density of LAF was 1.30 g/cm3 (range 1.27-1.33) determined by CsCl isopycnic ultracentrifugation; the partial specific volume was about 0.72 (range 0.70-0.74). The MW was calculated to be 18,000 daltons (range 16,400-19,600) with the Svedberg equation. The frictional ratio was 1.25.