<unk>  is a human blood group<unk>  based upon genes on chromosome 19. There are two types of<unk><unk> s,<unk>  a and<unk>  b. They are the only red cell<unk> s which are not produced by the erythrocyte itself. Instead, it is a component of body secretions, and is subsequently adsorbed onto the surface of the erythrocyte.
Lewis antigen system
Cluster of differentiation
Triage tag
Serotype
Pattern recognition receptor
Diphtheria classification
Striae
Ureaplasma urealyticum classification