CHARACTERIZATION OF SUPPRESSIVE IMMUNOGLOBULIN-BINDING FACTOR (IBF) .2. PURIFICATION AND MOLECULAR-WEIGHT DETERMINATION OF IBF PRODUCED BY L-5178-Y THETA-POSITIVE LYMPHOMA

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  • 1 January 1977
    • journal article
    • research article
    • Vol. 119  (4) , 1269-1274
Abstract
L-5178-Y [mouse] thymoma cells were used to produce radioactive IBF. The cells were internally labeled by incubation with radioactive amino acids and/or fucose. The supernatants contained radioactive material that bound to Ig[immunoglobulin]G-sensitized erythrocytes and suppressed the in vitro antibody response to sheep red blood cells. Upon filtration on Sephadex G-200, the IgG-binding activity and the suppressive activity eluted at peaks of 140,000 and above 300,000 d [daltons]. On SDS [sodium dodecyl sulfate] polyacrylamide gels, after precipitation with antigen-IgG-antibody complexes, IBF was found in a single peak of 80,000 d. This molecule could be dissociated in the presence of mercaptoethanol into a major unit of 40,000 d and a minor unit of 20,000 d. These data suggest that IBF is a molecule of 80,000 d, which contains chains of 40,000 d and probably 20,000 d linked by disulfide bridges. In cell supernatants the factor exists in polymeric forms of 140,000 d and more than 300,000 d.