Antagonistic mutant proteins of interleukin-4.

Interleukin-4 is a major regulator of the immune system, directing e.g. induction of a TH2 phenotype in T-cells, activation of B-cells and synthesis of IgE type antibodies, which are associated with allergic responses. Site-directed mutagenesis has revealed two sites important for receptor interaction on IL-4: site I mediates binding to the IL-4 receptor alpha subunit, and site II is involved in signal transduction through the receptor complex. Specific mutations in site II produced a series of ligands which bound to the receptor with high affinity, but had little or no agonistic activity and inhibited effects of wild type IL-4. The closely related cytokine IL-13, also a mediator of allergic processes, is antagonized as well. Antagonistic site II mutants of human IL-4 are therefore effective inhibitors with therapeutic potential for IL-4 associated diseases like type I hypersensitivity and asthma.