Lewis Blood Group System

• Identifying and differentiating blood group systems requires identifying antigens and antibodies.

Lewis Blood Group

• ISBT number and symbol are 007 or LE.
• Le gene (FUT3) on chromosome 19, Se gene (FUT2).
• Possible phenotypes: Le(a+b-), Le(a-b+), Le(a-b-), Le(a+b+).
• Antibody testing can be enhanced through the use of enzyme-treated red blood cells.
• Primary antibody is IgM and does not cross the placenta.

Le gene (amorph)

• Other name is FUT3.
• Produces fucosyltransferase.
• Adds L-fucose to Type 1 precursor substances= Lewis antigen A; More secretion.

FUT 2

• Secretor gene.
• Adds fucose to Type 1 precursors in secretions.
• determines Secretor status, so ABH antigens are in fluids.

FUT 3

• Lewis gene.
• Adds fucose to Type 1 precursors in plasma, forms Le(a) and Le(b) Lewis antigens.

Lewis Antigen B

• Produced when FUT3 adds L-fucose on existing Lewis antigen B.
• Has Higher affinity for RBCs; More common in RBCs.

Characteristics of Lewis Antigens

• Antigens are not well developed on fetal RBCs + IgM antibody, do not cause HDFN.
• Enzymes are not fully developed which diminishes potency and efficiency (some not yet produced)
• Antigens resist ficin, papain, DTT, and glycine-acid EDTA enzyme treatments.
• Antigens: present on lymphocytes, platelets, pancreas, stomach, intestine, skeletal muscle, renal cortex, and adrenal glands.

P Blood Group

• PIPK (A4GALT) gene located on chromosome 22 and Globoside (B3GALTI) gene located on chromosome 3.
• P1, Pk, and NOR are under PIPK (003) blood group system and P and PX2 are under Globoside (028).
• LKE is under Globoside collection.

Collection vs. System

• Antigens in the "collection" are serologically and biochemically similar to the "system" despite not fulfilling system criterias; genetics not fully explained.

P Blood Group Phenotypes

• Two common phenotypes: P1 and P2.
  • P1 phenotype: P, P1, Pk
  • P2 phenotype: Pk and P
• Three rare phenotypes: p (P null), P1k, and P2k; p is more common in Japan, North Sweden, and Amish group.
• Plk - P1, Pk and P2k - Pk

Characteristics of P Blood Group Antigens

• Synthesized by sequential action of glycosyltransferases (add sugars to precursor substances); not found in secretions.
• Antigens are resistant to ficin, papain, DTT, chloroquine, and glycine-acid EDTA treatments.
• Enhanced antibody reactivity uses enzyme-treated RBCs.

I system

• Formed by glycosyl transferases that create I (branched carbohydrate) and i (linear carbohydrate).
• High-prevalence antigens with reciprocal and developmentally regulated relationship.
• No true I-negative and i-negative phenotype; some appear not to change i status at birth (rare i adult).
  • Small i predominantly found in fetus and newborns (before 18 months or 2 years; gene not yet known); Enzyme is only fully developed after 18 months to 2 years; Small i is converted after some time however not every small i will be converted to large I.
• Large I found in adults.

I System Antigens

• Treatment of RBCs with ficin and papain increases activity of I and i antigens.

I System Antibodies

• Anti-I is a common autoantibody found in most sera.
• testing at 4°C and/or enzyme-treated RBCs increases detectable activity.
• Autoanti-I found in serum of normal healthy individuals is benign.
• Autoanti-I may be stimulated by microorganisms carrying I-like antigen on their surface.
  • Patients with M. pneumoniae develop strong cold agglutinins with I specificity
• Anti-i is not associated with HDFN because antibody is IgM and I antigen is poorly expressed on infant RBCs.
• Autoanti-i is fairly rare; strong reactions with cord RBCs and i adult RBCs and weaker reactions with I adults.

MNS Blood Group System - M and N Antigens

• Found on glycophorin A (GPA) : RBC protein that helps determine blood type, keeps cells separated, and slippery surface.
• M and N are antithetical and differ in amino acid residues at positions 1 and 5:
  • M = serine at position 1 and glycine at position 5.
  • N = leucine and glutamic acid at these positions, respectively.
• Destroyed by ficin, papain, bromelin, trypsin, and pronase enzymes.
  • Position 1 Amino Acid of M is Serine, N is Leucine.
  • Position 5 Amino Acid of M is Glycine and N is Glutamic acid.
• M and N antigen: Produced by GYPA gene.

S and s Antigens

• Located on glycophorin B (GPB).
• Differentiated by amino acid at position 29 of GPB.
  • Methionine defines S while Threonine defines s.
• Less easily degraded by enzymes because of antigen and enzyme-sensitive sites.
• Ficin, papain, bromelin, pronase, and chymotrypsin destroys S and s activity.

MNS Antibodies

• Anti-M are naturally occurring saline agglutinins that react below 37 degree Celsius; Predominantly IgG or have IgG component ( 50% to 80% IgG or have an IgG component) .
• Do not bind complement regardless of Ig class, and do not react with enzyme-treated RBCs.
• Anti-M significance decreases as anti-M does not react at 37 degrees Celsius, it is not significant for transfusion and can be ignored. - Anti-M rarely causes HTRs, decreased red blood cell survival, or HDFN

ANTI-N / ANTI-S / ANTI-s

• Similar to anti-M with cold-reactive IgM or IgG saline agglutinin does not bind complement or react with enzyme-treated RBCs: Not clinically significant unless it reacts at 37 degrees Celsius or Less common than anti-M.

Anti-S and Anti-s

• Mostly IgG, reactive at antiglobulin phase of testing with few expressing reactivity between 10 and 22 degree Celsius by saline IAT; May or may not react with enzyme-treated RBCS.
• Significant more often (bind complement) that can implicated in severe HTRs caused by hemoglobinuria and HDFN.

Kell and Kx Antigens

• The Kx antigen ( ISBT number 019, and symbol XK) as the only antigen in the Kx system with Kell antigens on RBCs while the Kx antigen is found in erythroid tissues and other tissues (brain, lymphoid organs, heart, and skeletal muscle).
• After ABO, K is rated second only to D in immunogenicity!

Kell and Kx Antibodies

• Anti-K as the most common antibody outside of ABO and Rh antibodies that is usually IgG and reactive in the antiglobulin phase (caused by pregnancy and transfusion and can persist for many years); implicated in severe HTR and also associated with severe HDFN.
• Kx antigen is present on all except those of rare McLeod phenotype that K0 and Kmod phenotype RBCs have increased Kx antigen.

Duffy Blood Group

• Duffy antigens include Fya and Fyb being important in routine blood bank with the system identified as early as 6 weeks AOG (well developed at birth) while identified in brain, colon, endothelium, lung, spleen, thyroid, thymus, and kidney cells.
• The two antigens Fy and Fyb are destroyed by ficin, papain, bromelin, and chymotrypsin + ZZAP enzymes while antibodies are usually IgG and enhanced in a low-ionic strength medium (do not react with enzyme-treated RBCs to help identify other antibodies when multiple antibodies are present).
• Once identified, anti-Fya and anti-Fyb + delayed HTRs = giving Fy(a-) or Fy(b-) blood.
• Fy3 antigen is only produced in presence of either (or both) a and b antigens = not destroyed by enzymes, where anti-Fy3 is rare antibody by Fy(a-b-).
• Majority of African Americans tested were Fy(a-b-) and resist infections by Plasmodium vivax and Plasmodium knowlesi.

Kidd Blood Group System

• Kidd antigens include Jka, Jkb, and Jk3 being found in RBCs of most individuals and well-developed on RBCs of neonates despite antigen treatment with enzymes affecting them.
• Kidd Antibodies are IgG that are made in response to transfusion or pregnancy: enhanced antibody reactivity (LISS or PEG, four drops instead of two)
• A strong antibody identified after transfusion maybe undetectable in a few weeks or months and people with null phenotype Jk(a-b-) lack Jka, Jkb, and Jk3.

Lutheran Blood Group System

• Lutheran antigens are usually either high prevalence (only few people lack the antigens = less can make alloantibody) or very low prevalence (only few people are exposed to the antigens) with antigen detection on fetal RBCs as early as 10 to 12 weeks of gestation (poorly developed at rare HDFN (only mild).
• Antigens are resistant to enzymes ficin and papain and to glycine-acid EDTA treatment as the main antibody (do not react with RBCs treated with sulfhydryl reagents DTT and AET).

Questions to Note

• The antigens are not technically found on the RBC (secretions and plasma; found in the RBCs and stick on surface) while testing with antibodies of the Lewis blood group system.
• The reactivity of the antibodies with the Lewis blood group is reduced when using enzyme-treated RBCs as naturally occurring from made by Le(a-b-).
• *The M, N, S, and s are destroyed by DTT as incorrect from all choices of MNS antigens.
• ABO > D > Kell antigens (in immunogenicity).
• Fy3 antigen is resistant to ficin and papain (while Fy(a) and Fy(b) which are destroyed by these enzymes) from Duffy blood group antigens.