JAK4, or Janus kinase 4, is an enzyme that plays a crucial role in the signaling pathways of the immune system. It is part of the JAK family of proteins, which are involved in transmitting signals from various cytokines and growth factors. This signaling is essential for the development and function of immune cells. Inhibitors of JAK4 are being studied for their potential in treating autoimmune diseases and inflammatory conditions, such as rheumatoid arthritis and psoriasis. By blocking JAK4, these medications aim to reduce inflammation and improve symptoms in affected individuals.