Rhofaktort

Rhofaktort, commonly called the Rh factor, refers to a group of antigens on the surface of red blood cells, with the D antigen being the most clinically significant. Individuals who carry the D antigen are Rh-positive; those who lack it are Rh-negative. The Rh system is one of the major blood group systems used to determine transfusion compatibility and pregnancy risk.

The D antigen is a transmembrane glycoprotein encoded by the RHD gene. Its presence or absence largely defines the Rh phenotype, but several other antigens in the Rh system (such as C/c and E/e) can form different Rh variants. Population frequencies of Rh positivity vary by ethnicity and region; Rh-negative individuals are more common in some populations, less so in others.

Clinical relevance: Rh incompatibility between an Rh-negative individual and an Rh-positive donor or fetus can lead to the production of anti-D antibodies. In transfusion medicine, this can cause hemolytic transfusion reactions if incompatible blood is given. In obstetrics, maternal anti-D antibodies can cross the placenta and cause hemolytic disease of the fetus and newborn in future pregnancies. Prevention includes Rh immune globulin (Rho(D) immune globulin) given to Rh-negative pregnant people and after exposure to Rh-positive blood to prevent sensitization.

Testing and use: Blood typing includes serologic testing for the D antigen to determine Rh status, guiding transfusions and prenatal care. Molecular methods can resolve rare or weakly expressed Rh traits.

History: The Rh factor was identified in 1940 by Karl Landsteiner and Alexander S. Wiener from experiments with rhesus monkeys; the term has since become standard in clinical medicine.