Rhesus System

The Rhesus system describes a group of different red cell antigens, the main one of which is D. In the U.K. 85% of individuals have red cells with the D antigen and these are Rhesus(+), whilst the remainder of individuals are Rhesus(-) with the D antigen absent.

Rhesus Testing

A small sample of blood is mixed with serum containing anti-D antibodies. Agglutination indicates Rhesus(+) whilst no agglutination indicates Rhesus(-).