Lymphotactin

Lymphotactin is a small secreted protein that functions primarily as a chemokine involved in immune cell trafficking. It is encoded by the LITAF gene in humans. Unlike many chemokines, lymphotactin can adopt two distinct conformations: a classic chemokine fold and a molten globule state, each capable of binding the same receptor but inducing different signaling pathways.

The protein is a member of the CC chemokine family and is processed as a precursor before secretion. Its sequence contains the characteristic cysteine residues that form disulfide bridges essential for structural stability. Phosphorylation of residues within the N‑terminal tail modulates its interaction with the chemokine receptor CXCR3, which is expressed on activated T cells and natural killer cells.

Functional studies show that lymphotactin attracts various leukocyte subtypes, including neutrophils, eosinophils, and basophils, to sites of inflammation. It also plays a role in the development of lymphoid tissues during embryogenesis, influencing the organization of lymph nodes. In disease contexts, elevated levels of lymphotactin have been detected in chronic inflammatory conditions such as rheumatoid arthritis and inflammatory bowel disease, suggesting a contribution to pathological inflammation.

The dual-structure property of lymphotactin makes it a unique tool for studying protein folding and receptor activation. Its involvement in chemotaxis and immune regulation has prompted investigations into its potential as a therapeutic target for modulating immune responses in autoimmune disease and cancer immunotherapy.