Lectin that binds saccharides with a free amino group, such as glucosamine or galactosamine. Binding to oligomeric saccharides is much stronger than binding to mono- or disaccharides. Also binds chitin and heparin. Has weak hexosaminidase activity but no chitinase activity. Has chemotactic activity for T-lymphocytes, bone marrow cells and eosinophils. May play a role in inflammation and allergy. Hydrolysis of terminal non-reducing N-acetyl-D-hexosamine residues in N-acetyl-beta-D-hexosaminides. 4-methylumbelliferone-N-acetylglucosamine (MU-(GlcNAc)1) is a GlcNAc2 analog. Optimum pH is 4.5-5.0. Predominantly localizes to the lumen of rough endoplasmic reticulum (rER) and nuclear envelope in alveolar macrophages. Localizes to the dilated lumen of rER in immature neutrophils in spleen and in cytoplasmic granules in peritoneal neutrophils. Detected in needle-shaped crystals present in the cytoplasm of bone marrow macrophages. Expressed in peritoneal cavity macrophages and in peritoneal and bone marrow-derived neutrophils. Abundantly expressed in bone marrow, with moderate levels detected in gastric antrum, spleen and in alveolar macrophages in lung. Not detected in brain, heart, liver, kidney, stomach, intestine, skeletal muscle, ovary, testis, thymus and lymph nodes (at protein level). Detected at low levels in bone marrow, spleen, thymus and lung. Barely detectable in intestine, kidney and coecum. In yolk sac, first detected at low levels at 8.5 dpc, with significant expression detected at 10.5 dpc in myeloid precursor cells. In liver, expressed from 16.5 dpc to P7.5 with highest levels detected from 18.5 dpc to P0.5. In spleen, first detected at 16.5 dpc, with peak levels detected at 18.5 dpc and P0.5 and expression persisting through the spleen maturation to the adult stage. In bone marrow, high expression levels detected from 16.5 dpc until adulthood. In lung, first detected around the time of birth, with levels increasing significantly from P14.5 towards adulthood. Up-regulated in response to IL3 and IL4, during the inflammatory response and upon parasitic infection. Belongs to the glycosyl hydrolase 18 family. Chitinase class II subfamily.