CHARACTERIZATION OF SUPPRESSIVE IMMUNOGLOBULIN-BINDING FACTOR (IBF) .3. BIOCHEMICAL AND IMMUNOCHEMICAL CHARACTERISTICS OF IBF PRODUCED BY ACTIVATED T-CELLS

  • 1 January 1978
    • journal article
    • research article
    • Vol. 121  (2) , 777-783
Abstract
The biochemical characteristics of IBF produced by activated thymus derived cells (ATC) [mouse] were investigated. For this purpose, supernatants of ATC were purified by affinity chromatography on insolubilized Ig[immunoglobulin]G and the eluted material was iodinated (125I), treated with mercaptoethanol and run on SDS [sodium dodecyl sulfate] polyacrylamide gels. The radioactivity was found in 2 peaks corresponding to MW of 38,000 d [dalton] and 18,000 d. This result extends and confirms previous findings that IBF produced by ATC is identical to IBF produced by L-5178-Y internally labeled [mouse] thymoma cells. The effect of various pH, temperatures and proteolytic and glycolytic enzymes on the binding properties of 3H-leucine-or H-fucose-labeled IBF to IgG and on the polyacrylamide gel profiles was also studied. By all these criteria, IBF appeared to be a glycoprotein in which the presence of the 38,000 to 40,000 d chain is necessary for the binding to IgG. In the attempt to study the relationships between IBF and I-region products, purified IBF produced by ATC was incubated with anti-Ia [immune response associated] immunoadsorbent, and the eluted material was iodinated and run on gels. The 38,000 d and 18,000 d chains characteristic of IBF were specifically retained on the relevant immunoadsorbent. Apparently IBF bears or is associated with Ia determinants.