Lacritin is a 12.3 kDa tear glycoprotein that is apically released from human lacrimal acinar cells during reflex tearing and can be detected in mixed reflex and basal human tears. Lacritin is produced by corneal, conjunctival, meibomian as one of the most eye-restricted genes. However it has been detected in a subpopulation of ductal cells in salivary glands, thyroid and mammary glands. Lacritin modulates lacrimal acinar cell secretion, promotes ductal cell proliferation, and stimulates signaling through tyrosine phosphorylation and release of calcium.