The Enigmatic Charcot-Leyden Crystal Protein (Galectin-10): Speculative Role(s) in the Eosinophil Biology and Function

Eosinophilic inflammation in peripheral tissues is typically marked by the deposition of a prominent eosinophil protein, Galectin-10, better known as Charcot-Leyden crystal protein (CLC). Unlike the eosinophil’s four distinct toxic cationic proteins and enzymes [major basic protein (MBP), eosinophil-derived neurotoxin (EDN), eosinophil cationic protein (ECP), and eosinophil peroxidase (EPO)], there is a paucity of information on the precise role of the crystal protein in the biology of the eosinophil. While its clinical significance at inflammatory foci remains highly speculative, its relative abundance (~10% of total eosinophil protein), as well as its dual nuclear and cytosolic localization is, however, suggestive of its biological and functional significance. In this article, we present a short review of the Charcot-Leyden crystal protein, specifically highlighting its most recently delineated modulatory role in regulatory T lymphocytes, and its speculative intracellular and extracellular role(s) in eosinophil function or associated inflammatory responses.