Landsteiner and Wiener's Rh blood group

Karl Landsteiner's discovery of the ABO blood groups in 1901 had made transfusion far safer, yet a noticeable share of patients still had hemolytic reactions after transfusion. At the Rockefeller Institute for Medical Research in New York, Landsteiner kept looking for other antigens on red cells. In 1927 he and Philip Levine described the M, N and P antigens.

In the new work Landsteiner and Wiener injected red cells from rhesus monkeys (Macaca mulatta) into rabbits, which made antibodies against them. Even after it was absorbed with selected human blood, the rabbit serum still clumped the red cells in 39 of 45 other human samples, whatever their ABO group or MN type. Some people carried the antigen it detected and others lacked it. They called it the Rh factor, after the monkey, and people became Rh-positive or Rh-negative. The first report appeared in 1940 in the Proceedings of the Society for Experimental Biology and Medicine. A fuller paper in the Journal of Experimental Medicine in 1941 described an agglutinogen that reacted both with the anti-rhesus sera and with antibodies found in human blood.

The factor explained hemolytic disease of the fetus and newborn. When an Rh-negative mother carries an Rh-positive fetus, fetal red cells can enter her bloodstream during pregnancy or birth and lead her to make anti-Rh antibodies. In a later pregnancy with an Rh-positive fetus, those antibodies cross the placenta and destroy the baby's red cells. Rh-positive and Rh-negative labels also became standard in blood typing to prevent transfusion reactions.

Later research showed that Rh is a system of several antigens, including D, C, c, E and e. D provokes the strongest immune response, so Rh status usually means the presence or absence of D. Rho(D) immune globulin, developed in the 1960s, stops Rh-negative mothers from forming the antibodies and has greatly reduced the disease.