IL4 is a pleiotropic cytokine produced by activated T cells. IL4 is a ligand for interleukin 4 receptor. The interleukin 4 receptor also binds to IL13，which may contribute to many overlapping functions of this cytokine and IL13. STAT6，a signal transducer and activator of transcription，has been shown to play a central role in mediating the immune regulatory signal of this cytokine. This gene，IL3，IL5，IL13，and CSF2 form a cytokine gene cluster on chromosome 5q，with this gene particularly close to IL13. IL4，IL13 and IL5 are found to be regulated coordinately by several long-range regulatory elements in an over 120 kilobase range on the chromosome. Two alternatively spliced transcript variants of this gene encoding distinct isoforms have been reported.
