Physicochemical characterization of a PMN-derived soluble fraction that enhances lymphocyte DNA synthesis.

Abstract

Abstract A lymphocyte DNA synthesis-potentiation factor was elaborated from an alum-stimulated mouse PMN preparation. A large part of this factor was thought to be elaborated from PMN and not from contaminated macrophages (2%), because alum was more effective than LPS in the production of the factor from PMN preparation, whereas LPS was more effective than alum in the production of a similar biologic activity from a macrophage preparation. 2-Chloroadenosine, which was cytotoxic for macrophages but not for PMN, did not affect the production of this factor from PMN, but greatly reduced the production of a similar activity from macrophages. The PMN factor, purified by ammonium sulfate precipitation, repeated Sephadex G-75 gel filtration, and isoelectrofocusing, was composed of two isoelectrophoretically distinct factors, a cationic (pi 9.8) and a neutral (pi 5.4) PMN factor. The two purified, 125I-labeled PMN factors were homogeneous on SDS-PAGE. A parallel study on 125I-labeled PMN factors and their thymocyte DNA synthesis-potentiation activity revealed several physico-chemical properties of these molecules. The cationic and neutral PMN factors, respectively, showed physical constants of 20.2 A and 22.2 A for the Stokes radius; 2.3 S and 2.3 S for the sedimentation coefficient; 1.326 g/cm3 and 1.296 g/cm3 for the buoyant density; 0.705 and 0.726 for the partial specific volume; and 10.62 × 10−7 cm2/sec and 9.66 × 10−7 cm2/sec for the diffusion constant. The m.w., calculated from these data by the Svedberg equation, was 19,000 for the cationic and 21,000 for the neutral PMN factor. The frictional ratios were 1.16 for the cationic and 1.22 for the neutral factor.