Major Antigens

There are approximately 40 antigens in the Rh system, and it is one of the most complex BGS that exists. The D antigen is by far the most important antigen in the system (because of its immunogenicity), and it determines whether a person is Rh-positive or Rh-negative. After D, the most important antigens are C, c, E and e.

Chemically, Rh antigens are proteins (polypeptides). They are not glycosylated and are hydrophobic.

Distribution in the Body and Development at Birth

Rh antigens are only present on red cells and are well developed at birth. The antigens appear to develop very early in fetal life.

Frequencies and Racial Variations

The frequencies of the common antigens and genotypes in Caucasians are provided later (see Table 5-1 in Nomenclatures). Several racial variations exist. These include (1) 90% of Afro-Americans are Rh(D)-positive, (2) both the Ro (cDe) and weak D (Du) phenotypes have a higher frequency in Blacks compared to Caucasians; (3) some antigens (e.g., V and VS) are almost exclusively confined to Blacks; (4) in parts of the Far East, almost 100% of people are Rh(D)-positive.

Enrichment Activity 1

Read Rh(D) in Taiwan, a Medline abstract of a modified pretransfusion testing protocol based on D antigen frequency in the Far East.

E-mail replies to Pat.

  1. What is the modified pretransfusion protocol that the authors used?

  2. For every 1000 random transfusion recipients in Taiwan, how many are capable of producing anti-D?

  3. Do you believe that the modified protocol is justified?

  4. Suggest evidence (not mentioned in the abstract) that could be used to support the protocol.