Specific antagonism of type I IL-4 receptor with a mutated form of murine IL-4.

IL-4 is a pleiotropic cytokine that is essential for the differentiation of Th2 cells and is critically involved in the pathogenesis of certain infectious and allergic diseases. We have produced and functionally characterized a mutant of murine IL-4 (IL-4.Y119D) as a potential antagonist of IL-4. The analysis of IL-4R binding revealed no differences between wild-type and mutated IL-4. Despite this finding, IL-4.Y119D was unable to induce proliferation of several IL-4-responsive T cell lines mediated via the type I IL-4R (IL-4Ralpha/common gamma chain (gamma c chain)) and specifically inhibited the proliferative effect of wild-type IL-4. In contrast, with IL-4.Y119D we found induction of MHC class II and CD23 molecules on resting splenic B cells as well as proliferation of B9 plasmocytoma cells. In addition, IL-4.Y119D induced mRNA for soluble IL-4R, leading to the release of soluble IL-4R protein by spleen cells. In macrophages, mutated IL-4 in combination with IFN-gamma induced TNF-alpha-dependent killing of Leishmania major parasites such as wild-type IL-4. The agonistic effects of IL-4.Y119D were observed on cells expressing the IL-13R alpha-chain, including an IL-13R alpha-chain transfected T cell line, but were absent in T cells that lack this molecule, indicating that IL-4.Y119D conveys its activity via the type II IL-4R (IL-4Ralpha/IL-13Ralpha). The described IL-4 mutant, therefore, represents a new tool to use in dissecting different IL-4 functions that are mediated by either type I or type II IL-4R complexes.