JAK1, or Janus kinase 1, is an enzyme that plays a crucial role in the signaling pathways of the immune system. It is part of the JAK-STAT signaling pathway, which helps transmit signals from various cytokines and growth factors to the cell nucleus, influencing gene expression and immune responses. Mutations or dysregulation of JAK1 can lead to various health issues, including autoimmune diseases and certain types of cancer. Targeting JAK1 with specific inhibitors is a therapeutic strategy being explored for conditions like rheumatoid arthritis and psoriasis, aiming to reduce inflammation and improve patient outcomes.