C1q R1 is also known as CD93, collectin receptor, and AA4 antigen, belongs to the Group XIV C-Type lectin family which play a role not only in cell–cell adhesion processes but also in host defence. All of them contain a C-type lectin domain, a series of epidermal growth factor like domains (EGF), a highly glycosylated mucin-like domain, a unique transmembrane domain and a short cytoplasmic tail. C1q R1 has also been identified as a hematopoietic stem cell marker.