CD93 (Cluster of Differentiation 93) is a C-type lectin transmembrane receptor which plays a role not only in cell–cell adhesion processes but also in host defense. Then this molecule was shown to be expressed on an early population of hematopoietic stem cells, which give rise to the entire spectrum of mature cells in the blood. Now CD93 is known to be expressed by a wide variety of cells such as platelets, monocytes, microglia and endothelial cells. In the immune system CD93 is also expressed on neutrophils, activated macrophages, B cell precursors until the T2 stage in the spleen, a subset of dendritic cells and of natural killer cells. CD93 is re-expressed during the late B cell differentiation and CD93 can be used in this context as a plasma cell maturation marker. CD93 has been found to be differentially expressed in grade IV glioma vasculature when compared to low grade glioma or normal brain and its high expression correlated with the poor survival of the patients. CD93 was initially thought to be a receptor for C1q, but now is thought to instead be involved in intercellular adhesion and in the clearance of apoptotic cells. The intracellular cytoplasmic tail of this protein contains two highly conserved domains which may be involved in CD93 function. Indeed, the highly charged juxta membrane domain has been found to interact with moesin, a protein known to play a role in linking transmembrane proteins to the cytoskeleton and in the remodeling of the cytoskeleton. This process appears crucial for both adhesion, migration and phagocytosis, three functions in which CD93 may be involved.
Protein expression analysis
Strain specific CD93 expression analysis in heterozygous B-hCD93 mice by flow cytometry. Bone marrow were collected from wild type and heterozygous B-hCD93 mice (H/+) , and analyzed by flow cytometry with species-specific CD93 antibody. Mouse CD93 was detectable in wild type mice and heterozygous B-hCD93 mice. Human CD93 was exclusively detectable in heterozygous B-hCD93 mice but not in wild type mice.