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Rhesus factor Syllabification: Rhe·sus fac·tor
Pronunciation: /ˈrēsəs ˌfaktər/
(abbreviation: Rh factor)

Definition of Rhesus factor in English:


[in singular]
An antigen occurring on the red blood cells of many humans (around 85 percent) and some other primates. It is particularly important as a cause of hemolytic disease of the newborn and of incompatibility in blood transfusions.
Example sentences
  • The discovery of the rhesus factor in human blood by American scientists also had important implications for blood grouping and, ultimately, for the development of human genetics.
  • Anti-D injections are used to counteract the rhesus factor if it proves necessary after a blood test.
  • The rhesus factor protein is the next most important one after the A and B proteins.


1940s: Rhesus from rhesus monkey, in which the antigen was first observed.

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