The invention provides methods and compositions for identifying pharmacological agents useful in the diagnosis or treatment of disease associated with the expression of a gene modulated by an interleukin 4 signal transducer and activator of transcription, IL-4 Stat. IL-4 Stat peptides and IL-4 receptor peptides and nucleic acids encoding such peptides find therapeutic uses. The subject compositions include IL-4 Stat and IL-4 receptor proteins, portions thereof, nucleic acids encoding them, and specific antibodies. The disclosed pharmaceutical screening methods are particularly suited to high-throughput screening where one or more steps are performed by a computer controlled electromechanical robot comprising an axial rotatable arm.