Recombinant Mouse YM1/Chitinase 3-like 3 Protein, CF

Mouse Chitinase 3-like 3 (CHI3L3), also known as ECF-L (eosinophil chemotactic factor‑lymphocyte) or Ym1, is a secreted ~45 kDa glycoprotein that is a member of the glycosyl hydrolase family 18 (chitinase-like) protein family (1-4). Mouse CHI3L3 has no ortholog in humans, but shares 80% and 90% amino acid (aa) sequence identity with rat CHI3L3 and mouse CHI3L4 (also known as Ym2), respectively (3). Mouse CHI3L3 and CHI3L4 share partial overlap in cell type and tissue mRNA expression (2, 5). CHI3L3 is primarily secreted by alveolar and peritoneal macrophages during inflammation, for example, due to nematode infection and airway hyper-responsiveness (2-10). It is considered a marker for alternatively activated macrophages, and is also expressed in bone marrow myeloid precursors, activated microglia, bone marrow-derived immature mast cells, connective tissue-type mast cells, macrophages in erythroblastic islands, neutrophil granules in bone marrow, peritoneum and spleen red pulp, and IL‑4‑stimulated B cells and dendritic cells (DC) (2-13). Statins (cholesterol-lowering drugs) can up‑regulate CHI3L3 expression in DC and promote Th2 responses (11). CHI3L3 can form crystals when it is at high concentration in the macrophage cytoplasm (2, 3, 12, 13). Reports differ as to its enzymatic and binding properties, but CHI3L3 binding of chitin, GlcN polymer or heparin/heparan sulfate may be weak, and later studies do not indicate significant CHI3L3 chemotactic or enzymatic activity (3-5, 9, 12, 13). However, it is proposed to up‑regulate the adhesion molecules LFA‑1 (integrin alpha L beta 2) and ICAM-1, thus promoting cell-cell adhesion (14). CHI3L3 has also shown activity as a co-factor with RANKL or vitamin D in stimulating osteoclast differentiation (14, 15).