The Rh blood group system is complex, with over 45 antigens. The RhD gene encodes the highly immunogenic D antigen, which is the most important antigen of the Rh system. Approximately 85% of people are RhD positive, while 15% are RhD negative. The Rh system is the second most important blood group system after ABO in transfusion medicine due to the potential for alloimmunization against the D antigen during pregnancy or transfusion. Alloimmunization to the D antigen can cause hemolytic disease of the newborn.

2. The Rh(D) Antigen
Rh is the most complex system, with over
45 antigens
The complexity of the Rh blood group
Antignss is due to the highly polymorphic
genes that encode them.
Discovered in 1940 after work on Rhesus
monkeys
The 2nd
most important after ABO in the
cross-match test
Only the most clinically significant Ags
will be discussed

4. ID CARD
The ID card combined testing of forward and
reverse grouping as well as Rh D determination.
Positive: Agglutinated cells forming red line on
surface of gel
 Negative: Compact button of cells on the bottom
of microtube.

5. Rh blood group antigens are proteins
The antigens of the Rh blood group are proteins.
The RhD gene encodes the D antigen, which is a
large protein on the red blood cell membrane, &
the most important.

6. Rh Antigen Frequency
D antigen – 85%
d antigen – 15%
C antigen – 70%
c antigen – 80%
E antigen – 30%
e antigen – 98%
The presence or absence of D Ag determines if
the person is Rh+ or Rh-

8. Significance
After ABO, the Rh system is the second most important
system. This is because:
The D antigen is extremely immunogenic.
It causes the production of anti-D in 50 - 70% of Rh(D)
negative people who are exposed to the D antigen.
Moreover, anti-D is the most common cause of severe
HDN and can cause in Utero death.
Because of this, in blood transfusion, the patient and
donor are matched for Rh(D) type as well as ABO groups.
The C and E Ags are not as immunogenic as D, routine
typing for these Ags is not performed

9. • Weak expression of the Rh system on the RBC, (Du
)
• Du
red cells can be classified into three categories
according to the mechanism that account for the
Weak D antigen
Variants of D

11. Hemolytic disease of the Newborn (HDN)
Usually related to D antigen exposure and the formation
of anti-D
Usually results from D negative female and D positive
male producing and offspring.
The baby will probably be D positive.
1st
pregnancy not effected, the 2nd
pregnancy and on will be
effected-results in still birth, severe jaundice, anemia
related to HDN.
To prevent this occurrence the female is administered
RHIG.