Other Blood Group Systems

1. Other Blood Group Systems Renee Wilkins, PhD, MLS(ASCP)cm CLS 325/435 School of Health Related Professions University of Mississippi Medical Center

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. Major Blood Group Systems • Lewis • I • P • MNSs • Kell • Kidd • Duffy

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

5. Systems that Produce Cold-Reacting Antibodies

6. 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

7. Lewis inheritance • Lewis system depends on Hh, Se, and Le genes • le, h, and sedo 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. Examples: • Le se H  Le(a+b-) • Le Se H  Le(a-b+) • le H se  Le(a-b-) • le hh se  Le(a-b-)

8. Lewis Antibodies • Usually occur naturally in those who are Le(a-b-) • Other phenotypes RARELY produce the antibody • 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-)

9. I antigens • These antigens may be I or i • They form on the precursor chain of RBC • Newborns have i antigen • Adults have I antigen • i antigen (linear) converts to I (branched) as the child matures (precursor chain is more linear at birth) at about 18 months

10. I antibodies • Most people have autoanti-I (RT or 4°C) • Alloanti-I is very rare • Cold-reacting (RT or below) IgM antibody • Clinically insignificant • Can attach complement (no hemolysis unless it reacts at 37°) • Prewarming the tests can eliminate reactivity • Enzymes can enhance detection

11. I antibodies • Anti-I often occurs as anti-IH • This means it will react at different strengths with reagent cells (depending on the amount of H antigen on the RBC) • O cells would have a strong reaction • A cells would have a weaker reaction

12. Anti-I antibodies • Anti-I: • Associated as a cause of Cold Agglutinin Disease (similar to PCH) • May be secondary to Mycoplasma pneumoniae infections • Anti-i: • rare and is sometimes associated with infectious mononucleosis

13. P Antigen • Similar to the ABO system • The most common phenotypes are P1 and P2 • P1 – consists of P1 and P antigens • P2 – consists of only P antigens • Like the A2 subgroup, P2 groups can produce anti-P1 • 75% of adults have P1

14. P1 Antigen • Strength of the antigen decreases upon storage • Found in secretions like plasma and hydatid cyst fluid • Cyst of a dog tapeworm

15. P antibodies • Anti-P1 • Naturally occurring IgM • Not clinically significant • Can be neutralized by hydatid cyst fluid to reveal more clinically significant antibodies • Anti-P • Produced in individuals with paroxysmal cold hemoglobinuria (PCH) • PCH – IgG auto-anti-P attaches complement when cold (fingers, toes). As the red cells circulate, they begin to lyse (releasing Hgb) • This PCH antibody is also called the Donath-Landsteiner antibody

16. MNSs Blood System • 4 important antigens (more exist): • M • N • S • s • U (ALWAYS present when S & s are inherited) • M & N located on Glycophorin A • S & s and U located on Glycophorin B • Remember: Glycophorin is a protein that carries many RBC antigens

17. MNSs Antigens M & N only differ in their amino acid sequence at positions 1 and 5 M Glycophorin A N RBC S & s only differ in their amino acid sequence at position 29 S U s Glycophorin B COOH end ….. ….5, 4, 3, 2, 1 (NH2 end)

18. MNSs antigens • all show dosage • M & N give a stronger reaction when homozygous, (M+N-) or (M-N+) • Weaker reactions occur when in the heterozygous state (M+N+) • Antigens are destroyed by enzymes (i.e. ficin, papain)

19. U (Su) antigen • The U antigen is ALWAYS present when S & s are inherited • About 85% of S-s- individuals are U-negative (RARE) • U-negative cells are only found in the Black population

20. Frequency of MNSs antigens High-incidence antigen

21. Thought….. • Can a person have NO MNSs antigens? • Yes, the Mk allele produces no M, N, S, or s antigens • Frequency of 0.00064 or .064%

22. Anti-M and anti-N antibodies • Demonstrate dosage • Anti-M and anti-N • IgM (rarely IgG) • Clinically insignificant • If IgG, could be implicated in HDN (RARE) • Will not react with enzyme treated cells

23. Anti-S, Anti-s, and Anti-U • Clinically significant • IgG • Can cause RBC destruction and HDN • Anti-U • will react with S+ or s+ red cells • Usually occurs in S-s- cells • Can only give U-negative blood units found in <1% of Black population • Contact rare donor registry

24. MNSs Antibody Characteristics

25. Systems that Produce Warm-Reacting Antibodies

26. 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

27. Other Kell antigens • Other sets of alleles also exist in the Kell system: • Analogous to the Rh system: C/c and E/e • Kp antigens • Kpa is a low frequency antigen (only 2%) • Kpb is a high frequency antigen (99.9%) • Js antigens • Jsa (20% in Blacks, 0.1% in Whites) • Jsb is high frequency (80-100%)

28. Kell antigens • Kell antigens have disulfide-bonded regions on the glycoproteins • This makes them sensitive to sulfhydryl reagents: • 2-mercaptoethanol (2-ME) • Dithiothreitol (DTT) • 2-aminoethylisothiouronium bromide (AET)

29. Kellnull or K0 • No expression of Kell antigens except a related antigen called Kx • As a result of transfusion, K0 individuals can develop anti-Ku (Ku is on RBCs that have Kell antigens) • Rare Kell negative units should be given

30. Kell antibodies • 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 • k, Kpb, and Jsb antibodies are rare (many individuals have these antigens and won’t develop an antibody) • The other antibodies are also rare since few donors have the antigen

31. Kx antigen • Not a part of the Kell system, but is related • Kx antigens are present in small amounts in individuals with normal Kell antigens • Kx antigens are increased in those who are K0

32. McLeod Syndrome • The XK1 gene (on the X chromosome) codes for the Kx antigen • When the gene is not inherited, Kx is absent (almost exclusive in White males) • Causes abnormal red cell morphologies and decreased red cell survival: • Acanthocytes – spur cells (defected cell membrane) • Reticulocytes – immature red cells • Associated with chronic granulomatous disease • WBCs engulf microorganisms, but cannot kill (normal flora)

33. Kidd Blood Group • 2 antigens • Jka and Jkb (codominant alleles) • Show dosage

34. Kidd Antigens • Well developed at birth • Enhanced by enzymes • Not very acessible on the RBC membrane

35. 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

36. Kidd antibodies • Anti-Jk3 • Found in some individuals who are Jk(a-b-) • Far East and Pacific Islanders (RARE)

37. 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

38. 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

39. 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 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

40. Other Blood Group Antigens…

41. Lutheran Blood Group System • 2 codominant alleles: Lua and Lub • Weakly expressed on cord blood cells • Most individuals (92%) have the Lub antigen, Lu(a-b+) • The Lu(a-b-) phenotype is RARE

42. Lutheran antibodies • Anti-Lua • IgM and IgG • Not clinically significant • Reacts at room temperature • Mild HDN • Naturally occurring or immune stimulated • Anti-Lub • Rare because Lub is high incidence antigen • IgG • Associated with transfusion reactions (rare HDN)

43. Bg Antigens • Three (Bennett-Goodspeed) Bg antigens: • Bga • Bgb • Bgc • Related to human leukocyte antigens (HLA) on RBCs • Antibodies are not clinically significant

44. Sda Antigens • High incidence antigens found in tissues and body fluids • Antibodies are not clinically significant • Antibodies characteristically cause mixed field agglutination with reagent cells

45. Xg Blood Group • Only one exists (Xga) • Inheritance occurs only on the X chromosome • 89% Xga in women • 66% in males (carry only one X) • Men could be genotype Xga or Xg • Women could be XgaXga, XgaXg, or XgXg • Example: Xg(a+) male with Xg(a-) woman would only pass Xg(a+) to daughters, but not sons • The antigen is not a strong immunogen (not attributed to transfusion reactions); but antibodies may be of IgG class

46. HTLA Antigens • High Titer Low Avidity (HTLA) • Occur with high frequency • Antibodies are VERY weak and are not clinically significant • Do not cause HDN or HTR

47. Review

48. Cold Antibodies (IgM) • Anti-Lea • Anti-Leb • Anti-I • Anti-P1 • Anti-M • Anti-A, -B, -H • Anti-N LIiPMABHN Naturally Occurring

49. Warm antibodies (IgG) • Rh antibodies • Kell • Duffy • Kidd • S,s

50. Remember enzyme activity: Papain, bromelin, ficin, and trypsin