| Rh antigens (= agglutinogens) are one of many types of surface marker molecules made by red blood cells. The letters Rh are applied to these antigens because they were first identified by Landsteiner and Wiener in 1940 using antibodies against Rhesus monkey RBCs.
Chemically, Rh antigens are part of long proteins that coil back and forth through the RBC plasma membrane, forming six extracellular loops. The sequence of amino acids on extracellular loops 3, 4, and 6 determines the Rh antigen type.
Over 40 types of Rh antigens have been identified thus far, each differing in structure by just a few amino acids. Most common are the D antigens, and individuals who have these antigens are considered to be Rh+. About 85% of Caucasians, 90%-95% of Blacks, and 99% of Asians are Rh+. Individuals who have other types of Rh antigens are considered to be Rh-. |
