APC anti-mouse CD93 (AA4.1, early B lineage)

CD93 is a 130-140 kD C-type lectin-like type I transmembrane protein, also known as complement component 1, q subcomponent (C1qR1), C1qRp collectin receptor (C1qRp), or AA4 antigen. It is a receptor expressed on immature B lymphocytes, hematopoietic progenitors and stem cells in adult bone marrow, fetal liver, and the embryonic yolk sac. CD93 expression levels on splenic immature/transitional B cells is much lower than in bone marrow. It is reinduced during plasma cell differentiation and plays an important role in maintaining plasma cells in bone marrow niches. Immature dendritic cells express CD93 and down-regulate this molecule upon maturation, suggesting they play a role in uptake of particles. CD93 is also expressed on monocytes, macrophages, and endothelial cells. Macrophages from CD93 (-/-) mice had a significant phagocytic defect in the clearance of apoptotic cells in vivo, indicating CD93 may contribute to the in vivo clearance of dying cells. The idea that CD93 binds to C1q remains controversial.