1. Minor Blood Group Systems
Nada Mohamed Ahmed ,
MD, MT (ASCP)i

2. Facts Over 200 blood antigens exist!
Unfortunately, we only get to review the most relevant antigens
We will discuss each of these major antigens, their antibodies, and the clinical significance of each

3. Objectives of Minor Blood Group Systems
Lewis
Kell
Kidd Antibodies
Duffy Antigens
rare characteristic

4. Basic terms to remember
Clinical significance: antibodies that are associated with decreased RBC survival
Transfusion reactions
HDN
Not clinically significant: antibodies that do not cause red cell destruction
Cold reacting antibodies: agglutination best observed at or below room temp.
Warm reacting antibodies: agglutination best observed at 37°C
Dosage effect amount of the product of the gene.
Enzymes enhance activity they speed up reactions by providing an alternative reaction pathway of lower activation energy.

5. Lewis substance adheres to RBC becoming an antigen
Lewis Antigens
Soluble antigens produced by tissues and found in body fluids (plasma)
Adsorbed on the RBC
Lewis substance adheres to RBC becoming an antigen
RBC
Le substance in plasma
Le genes

6. Lewis inheritance Lewis system depends on Hh, Se, and Le genes
le, h, and se do not produce products
If the Le gene is inherited, Lea substance is produced
Le, H, and Se genes must ALL be inherited to convert Lea to Leb.

7. Lewis Antibodies Usually occur naturally in those who are Le(a-b-)
IgM (may fix complement, becoming hemolytic)
Enzymes enhance activity
May be detected soon after pregnancy because pregnant women may temporarily become Le(a-b-)
No clinical significance…Why?
Le antibodies in a patient can be neutralized by the Lewis antigens in the donor’s plasma (cancel each other out)
do not cause HDN because they do not cross placenta (antigens not developed well in cord blood)
Le(a-b-)
May become hemolytic in vitro (in the tube)
If pregnant women have Le antibodies detected, they need to first be neutralized so that HDN antibodies may be detected

8. Systems that Produce Warm-Reacting Antibodies

9. Kell System Similar to the Rh system 2 major antigens (over 20 exist)
K (Kell), <9% of population
k (cellano), >90% of population
The K and k genes are codominant alleles on chromosome 7 that code for the antigens
Well developed at birth
The K antigen is very immunogenic (2nd to the D antigen) in stimulating antibody production

10. Kell antibodies Clinically significant IgG (react well at AHG)
Produced as a result of immune stimulation (transfusion, pregnancy)
Clinically significant
Anti-K is most common because the K antigen is extremely immunogenic
antibodies are rare (many individuals have these antigens and won’t develop an antibody)

11. Kidd Blood Group 2 antigens Jka and Jkb (codominant alleles)
Show dosage
Genotype
Phenotype
Whites (%)
Blacks (%)
JkaJka
Jk(a+b-)
26.3
51.1
JkaJkb
Jk(a+b+
50.3
40.8
JkbJkb
Jk(a-b+)
23.4
8.1
JkJk
Jk(a-b-)
rare

12. Kidd Antigens Well developed at birth Enhanced by enzymes
Not very accessible on the RBC membrane

13. Kidd antibodies Anti-Jka and Anti-Jkb IgG Clinically significant
Implicated in HTR and HDN
Common cause of delayed HTR
Usually appears with other antibodies when detected

14. Duffy Blood Group Predominant genes (codominant alleles):
Fya and Fyb code for antigens that are well developed at birth
Antigens are destroyed by enzymes
Show dosage
Phenotypes
Blacks
Whites
Fy(a+b-) 9 17
Fy(a+b+) 1 49
Fy(a-b+) 22 34
Fy(a-b-) 68
RARE

15. Duffy antibodies IgG Do not bind complement Clinically significant
Stimulated by transfusion or pregnancy (but not a common cause of HDN)
Do not react with enzyme treated RBCs

16. The Duffy and Malaria Connection
Most African-Americans are Fy(a-b-)
Interestingly, certain malarial parasites (Plasmodium knowlesi and P. vivax) will not invade Fya and Fyb negative cells
It seems either Fya or Fyb are needed for the merozoite(infective stage of Malaria) to attach to the red cell
The Fy(a-b-) phenotype is found frequently in West and Central Africans, supporting the theory of selective evolution

17. Cold Antibodies (IgM) Naturally Occurring Anti-Lea Anti-Leb
Anti-A, -B, -H
Naturally Occurring

18. Warm antibodies (IgG)
Rh antibodies
Kell
Duffy
Kidd

19. Remember enzyme activity:
Enhanced by enzymes
Destroyed by enzymes
Kidd Rh
Lewis
Fya and Fyb
Papain, bromelin, ficin, and trypsin

20. Remembering Dosage: Kidds and Duffy the Monkey (Rh) eat lots of doses.
Jka, Jkb, Fya, Fyb, C, c, E, e (no D),
Kidd
Duffy Rh