This gene encodes a member of the tyrosine kinase and, more specifically, the Janus kinases (JAKs) protein families.This protein associates with the cytoplasmic domain of type I and type II cytokine receptors and promulgate cytokine signals by phosphorylating receptor subunits.It is also component of both the type I and type III interferon signaling pathways.As such, it may play a role in anti-viral immunity.A mutation in this gene has been associated with hyperimmunoglobulin E syndrome (HIES) - a primary immunodeficiency characterized by elevated serum immunoglobulin E.[provided by RefSeq]