The STX11 gene encodes a member of the syntaxin family (syntaxin 11) that localizes mainly between the endoplasmic reticulum and the Golgi. This protein plays a role in intracellular trafficking and targeting and fusion of intracellular transport vesicles. Specifically, it plays a role in binding the vesicles to the cell membranes. Within the immune system, STX11 has been shown to be vital for normal NK cell and CD8+ T cell cytotoxic granule exocytosis, and has also been implicated in neutrophil granule exocytosis.
Defects in this protein have been associated with Familial Hemophagocytic Lymphohistiocytosis Type-4 (FHL4), characterized by proliferation and infiltration of hyperactivated T cells, natural killer cells, B cells, and macrophages (histiocytes) manifesting as acute illness with prolonged fever, hepatosplenomegaly, and cytopenias. Recent studies also suggest that mutations in STX11 may play a role in the pathogenesis of peripheral T-cell lymphomas.