Other Blood Group Systems Terry Kotrla, MS, MT(ASCP)BB

Introduction Over 500 blood group antigens “High incidence”, “public” or “high frequency” antigens are those present on almost every person’s red blood cells “Low incidence”, “private” or “low frequency” antigens are present on very, very few individuals red blood cells

Introduction Each known antigen initially identified through the detection of its specific antibody in the serum. Knowledge of serologic behavior and characteristics of blood group antibodies is CRITICAL for identification

Introduction Essential when evaluating antibody screen and panel studies. Considerations given to: Phase of reactivity Antibody class involved Ability to cause HDFN and HTR

I Blood Group Related to ABO and Lewis by its biochemical structure Two antigens: I and i Fetal RBCs rich in i antigen and lack I antigen. First 2 years I develops, lose i Anti-I reacts most strongly with adult cells, negative or weakly with cord RBCs Strength of I antigen varies on adult cells Rare instances I never develops.

I Blood Group Anti-I is associated with cold agglutinin hemagglutinin disease Decreased expression of I and increased expression of i antigens is observed in: oncogenesis, thalassemias, sickle cell anemias, associated with congenital cataracts in Asian populations.

I Blood Group Antibodies: anti-I anti-I Anti-I Cause of non-specific agglutination in tests performed at RT Positive reactions with all cells tested: reverse, antibody screen and crossmatches May cause ABO discrepancy Can be detected in serum of most normal adults if serum is tested at 4C Associated with atypical pneumonia caused by M. pneumoniae , cold agglutinin titers used to monitor the disease. May cause hemolytic anemia when present in high titers

I Blood Group Anti-i associated with certain diseases Infectious mononucleosis Epstein-Barr virus Cytomegalovirus Antibody is rarely encountered

I Blood Group Clinical Significance Usually benign Clinically significant examples seen in Cold Agglutinin Syndrome (CAS) Antibodies are of high titer (1000>) High thermal amplitude Cause hemolytic anemia Transfuse blood through blood warmer Cannot cause HDFN Does not cause HTR

I Blood Group Serological Confirmation Test serum agains 3 adult O RBCs and 3 cord RBCs and an auto-control Adult cells and auto-control = positive Cord RBCs = negative/very weak positive Prewarmed technique will eliminate reactivity of most examples Reactivity enhanced using enzyme treated cells

I Blood Group Very strong examples of anti-I may react at AHG and require cold autoabsorption or rabbit erythrocyte stroma test (REST) to rule out presence of other antibodies. Collect EDTA blood samples, place at 37C Harvest EDTA cells, wash with 37C saline Place clotted blood sample at 4C, separate serum Add 1 mL serum to 1mL rbcs, incubate at 4C for 1 hour Harvest serum and test against screen cells, if negative, continue screen, if positive repeat absorption with new aliquot of RBCs

Lewis System Major antigens Lea and Leb , other antigens include Lec, Led and Lex Antigens ARE NOT intrinsic to RBCs but are absorbed from the plasma and inserted into RBC membrane.

Lewis System Antigenic Development Genetic control reside in single gene “Le” Amorph le, if homozygous will not have Lewis antigens Lea formed first, then modified to form Leb which is adsorbed preferentially over Lea Lewis phenotype of RBC can be changed by incubating with plasma containing Lea or Leb glycoplipid.

Lewis System Lewis Phenotypes and Their Frequencies White Black Le (a+b-) 22% 23% Le (a-b+) 72% 55% Le (a-b-) 6% Le (a+b+) Rare rare

Lewis System Lewis antigens in infants Antigens absent or extremely weak at birth Expression of Leb gradual Birth Le (a-b-) 2 months Le(a+b-) 12 to 18 months Le(a+b+) 2 to 3 years Le (a-b+)

Lewis System Lewis antigens and pregnancy Antigen strength may decline dramatically Transiently Le (a-b-) may produce Lewis antibodies during pregnancy Antigens return after delivery and antibodies disappear

Lewis System Interaction of Le, Se and H Genes lele will not have Lewis antigens, but if Se present will have A, B and H in secrections Genotype se/se and have one Lewis antigen will have Lea in their secretions but no A, B or H.

Lewis System Le (a+b-) Le (a-b+) Le (a-b-) Lewis Phenotype ABH Secretor Lewis Secretor Le (a+b-) All ABH NON-Secretors All Lea Secretors Le (a-b+) All ABH secretors All secretors of Lea and Leb Le (a-b-) 80% ABH secretors 20% ABH NON secretors NONE

Lewis System Lewis Antibodies Almost always IgM, react strongly at RT, may cause ABO discrepancy if reverse cells have Lewis antigen. Occur almost exclusively in Le (a-b-) and production of anti-Lea AND –Leb not unusual Anti-Lea frequently encountered, anti-Leb rarely encountered.

Lewis System Lewis Antibodies Although most react at RT reactivity may be seen at 37C, but is weaker and may be weakly reactive at AHG Can bind complement and cause IN-VITRO hemolysis, most often with enzyme treated cells Because antibodies are IgM and antigens are poorly developed at birth antibodies NOT implicated in HDFN.

Lewis System Lewis antibodies Can be neutralized in-vitro by additions of Lewis Substance Le antigens are present in secretions Add to serum with Lewis antibodies and the antibodies will be bound to the soluble Lewis antigens Useful when multiple antibodies are present and 1 is a Lewis, eliminates the activity of the antibody

Lewis System Transfusion Practice Transfused RBCs will acquire the Lewis phenotype of the recipient within a few days Lewis antibodies in patient will be neutralized by Lewis substance in donor plasma Lewis antibodies rarely cause in-vivo hemolysis It is not necessary to phenotype donors for Lewis antigens prior to transfusion, give crossmatch compatible

P Blood Group Whites Blacks P1 79% 94% P2 21% 6% Discovered 1927 when Landsteiner immunized rabbits with human RBCs Initially named “P” but as complexity of P blood group was discovered renamed “P1” RBCs lacking P1 are P2 Other P phenotypes exist but are rare(<1%): P, P1k and P2k Whites Blacks P1 79% 94% P2 21% 6%