title: In vitro and in vivo suppression of interleukin-2-activated killer cell activity by chimeric proteins between interleukin-2 and Pseudomonas exotoxin.
abstract: The biological effects of IL-2 are mediated through high (complex of alpha and beta chain) or intermediate (beta chain) affinity IL-2 receptors. Previously, chimeric proteins composed of IL-2 and Pseudomonas exotoxin (IL-2-PE) were shown to be specifically cytotoxic to cells bearing IL-2 receptors. It has also been shown that IL-2-PE chimeric proteins can abrogate T cell-mediated immune response in vitro. In the current study, we have investigated the effects of IL-2-PE on LAK activity both in vivo and in vitro. We administered either IL-2-PE40 (comprised of IL-2 and 40-kDa portion of PE) or IL-2-PE66 (comprised of IL-2 and 66-kDa molecule of PE) to normal C57BL/6 mice for 3 or 8 days and LAK activity was assessed in various organs of mice. We found that IL-2-PE40 generated LAK activity in various compartments of mice and the level of activity was slightly lower than that observed with an equivalent amount of recombinant (r) IL-2 alone. However, IL-2-PE66 failed to generate LAK activity which would have been induced due to an equivalent concentration of rIL-2. IL-2-PE66 also did not induce LAK activity from the splenocytes during in vitro culture while IL-2-PE40 generated good LAK activity. An equivalent amount of IL-2 also generated potent LAK activity. The suppression of LAK activity by IL-2-PE66 was also evident in cells preactivated with IL-2; however, this inhibition was partial. The suppressive activity of IL-2-PE66 was shown to be mediated through IL-2 receptor interactions as excess amounts of rIL-2 were able to abrogate its effect. Both IL-2 toxins were equivalently cytotoxic to IL-2 receptor-bearing HUT 102 cells and both were able to compete from high and intermediate affinity IL-2 receptors. Taken together, our data indicate that IL-2-PE66 is highly cytotoxic to LAK cells while IL-2-PE40 is less cytotoxic. Thus, data from our study and from other published reports indicate that IL-2-PE66 is more potent immunosuppressive agent than IL-2-PE40.
authors.affiliation: Laboratory of Cellular Immunology, Food and Drug Administration, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: R K
authors.initials: RK
authors.lastname: Puri
authors.forename: D
authors.initials: D
authors.lastname: FitzGerald
authors.forename: P
authors.initials: P
authors.lastname: Leland
authors.forename: R W
authors.initials: RW
authors.lastname: Kozak
authors.forename: I
authors.initials: I
authors.lastname: Pastan
mesh_terms: D036002:ADP Ribose Transferases; D000818:Animals; D001427:Bacterial Toxins; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D005098:Exotoxins / Q000737:chemistry* / Q000633:toxicity; D005260:Female; D007111:Immunity, Cellular / Q000187:drug effects; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism; D015979:Killer Cells, Lymphokine-Activated / Q000187:drug effects* / Q000276:immunology; D008213:Lymphocyte Activation / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D015375:Receptors, Interleukin-2 / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism / Q000633:toxicity; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
chemical_list: D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D005098:Exotoxins; D007376:Interleukin-2; D015375:Receptors, Interleukin-2; D011993:Recombinant Fusion Proteins; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A