Proteoglycan 3, also known as Eosinophil major basic protein homolog, Prepro-major basic protein homolog, PRG3 and MBPH, contains one C-type lectin domain. Proteoglycans are a major component of the animal extracellular matrix. PRG3 localizes to the eosinophil secondary granule and is expressed in bone marrow, not detected in placenta. PRG3 has similar cytotoxic and cytostimulatory activities to PRG2/MBP. In vitro, PRG3 can stimulate neutrophil superoxide production and IL8 release, histamine and leukotriene C4 release from basophils.