Biological characterization of human interleukin-2 mutant proteins. Structure-activity relationship studies.
Several human interleukin-2 (IL-2) mutant proteins have been produced previously by site-directed mutagenesis and found to have different capacities to induce T-cell proliferative activity. In this study, the abilities of these IL-2 mutant proteins to activate natural killer cells and to induce interferon-gamma production have been evaluated, and the binding of these proteins to IL-2 receptors analyzed. Natural killer cell activation and interferon-gamma induction assays showed that the relative activities of IL-2 mutant proteins were consistent with their relative activities in T-cell proliferation assay. Receptor-binding studies showed that the activities of most proteins correlated well with their respective affinities for high-affinity IL-2 receptors on CTLL-2 cells. Interestingly, although the mutant protein with deletion of cysteine 125 (des-Cys125) was biologically less active than the protein with substitution of alanine for cysteine 105 (Ala105), both proteins exhibited similar affinity. Des-Cys125, like IL-2 and Ala105, also caused down-regulation of high-affinity IL-2 receptors. Binding studies on MLA-144, a cell line expressing mainly intermediate-affinity IL-2 receptors (IL-2R beta), however, showed that des-Cys125 had much lower affinity than Ala105. These results suggest that binding of IL-2 and mutant proteins to the IL-2R beta component of the high-affinity receptor is essential for the induction of biological effects.
D000818:Animals; D002460:Cell Line; D006801:Humans; D007369:Interferon Inducers; D007371:Interferon-gamma / Q000096:biosynthesis; D007376:Interleukin-2 / Q000235:genetics* / Q000276:immunology; D007694:Killer Cells, Natural / Q000276:immunology; D008213:Lymphocyte Activation; D051379:Mice; D009154:Mutation; D011971:Receptors, Immunologic / Q000378:metabolism*; D015375:Receptors, Interleukin-2
D007369:Interferon Inducers; D007376:Interleukin-2; D011971:Receptors, Immunologic; D015375:Receptors, Interleukin-2; D007371:Interferon-gamma