Presentation on theme: "Unit 9 Other Blood Group Systems Part 1"— Presentation transcript:
1 Unit 9 Other Blood Group Systems Part 1 Terry Kotrla, MS, MT(ASCP)BB
2 IntroductionISBT recognizes 30 blood group systems with over 600 antigens.Some VERY rare only found in certain ethnic groups.Some associated with diseases or resistance to infection.Most important are ABO and D“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
3 IntroductionEach 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
4 IntroductionEssential when evaluating antibody screen and panel studies.Considerations given to:Phase of reactivityAntibody class involvedAbility to cause HDFN and HTR
5 Introduction Clinically insignificant Clinically significant Reactive in-vitro at ISIgM classIn-vivo- NO hemolysis/decreased RBC survivalClinically significantReactive in-vitro at 37C and/or AHGIgGIn-vivo implicated in HDFN and/or HTR.
6 Introduction For each blood group system you MUST know: Antigen development, if important.Antibody class usually involved.Phase of reactivity in in-vitro tests.Clinical significance.Whether donor units must be antigen negative.Any unique characteristics of the blood group antigens and/or antibodies.
7 IntroductionMost textbooks will divide discussion of the blood groups into two distinct groups:Cold reacting, considered nuisance, IgMWarm reacting, considered significant, IgGIf you know the phase of reactivity you will know the antibody class involved AND the clinical significance.
8 I/i Blood Group (ISBT 027)Related to ABO and Lewis by its biochemical structureTwo antigens: I and iFetal RBCs rich in i antigen and lack I antigen.First 2 years I develops, lose iAnti-I reacts most strongly with adult cells, negative or weakly with cord RBCsStrength of I antigen varies on adult cellsRare instances I never develops.
9 I/i Blood GroupAnti-I is associated with cold agglutinin hemagglutinin diseaseDecreased expression of I and increased expression of i antigens is observed in:oncogenesis,thalassemias,sickle cell anemias,associated with congenital cataracts in Asian populations.
10 I AntibodiesCause of non-specific agglutination in tests performed at RTPositive reactions with all cells tested: reverse, antibody screen and crossmatches regardless of ABO blood groupMay cause ABO discrepancyCan be detected in serum of most normal adults if serum is tested at 4CAssociated with atypical pneumonia caused by M. pneumoniae , cold agglutinin titers used to monitor the disease.May cause hemolytic anemia when present in high titers
11 Anti-i Anti-i associated with certain diseases Infectious mononucleosisEpstein-Barr virusCytomegalovirusThis antibody is rarely encountered
12 Clinical Significance of Anti-I Usually benignClinically significant examples seen in Cold Agglutinin Syndrome (CAS)Antibodies are of high titer (1000>)High thermal amplitudeCause hemolytic anemiaTransfuse blood through blood warmerCannot cause HDFN – TWO REASONSAntibody class is IgMAntigen not well developed on fetal RBCsDoes not cause HTR
13 Serological Confirmation of Anti-I Test serum agains 3 adult group O RBCs and 3 group O cord RBCs and an auto-controlAdult cells and auto-control = positiveCord RBCs = negative/very weak positiveReactivity enhanced using enzyme treated cells
14 Serological Confirmation of Anti-I O CordO AdultAC0/+w4+Row 1 of reactions confirms anti-IRow 2 of reactions indicates some “other” alloantibody.
15 Prewarmed Technique AHG Screen 1 Screen 2 Screen 3 Original 3+ Prewarmed technique will eliminate reactivity of most examplesOriginal reactions at AHGPrewarmed 1 – no other alloantibody present.Prewarmed 2 – alloantibody present which must be identified.AHGScreen 1Screen 2Screen 3Original3+Prewarmed 1Prewarmed 22+
16 Cold Autoabsorption of Anti-I 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 37CHarvest EDTA cells, wash with 37C salinePlace clotted blood sample at 4C, separate serumAdd 1 mL serum to 1mL rbcs, incubate at 4C for 1 hourHarvest serum and test against screen cells, if negative, continue screen, if positive repeat absorption with new aliquot of RBCs.
17 Lewis System (ISBT 007)Identified in 1946 and named after antibody maker, Mrs. Lewis.Major antigens Lea and Leb , other antigens include Lec, Led and Lex
18 Lewis Antigenic Development Antigens ARE NOT intrinsic to RBCs but are absorbed from the plasma and inserted into RBC membrane.Genetic control reside in single gene “Le”Amorph le, if homozygous will not have Lewis antigensLea formed first, then modified to form Leb which is adsorbed preferentially over LeaLewis phenotype of RBC can be changed by incubating with plasma containing Lea or Leb glycoplipid.
19 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+)Rarerare
20 Lewis System Lewis antigens in infants Antigens absent or extremely weak at birthExpression of Leb is gradualBirth Le (a-b-)2 months Le(a+b-)12 to 18 months Le(a+b+)2 to 3 years Le (a-b+)Lewis antigens cannot be used for paternity testing on infants.
21 Lewis Antigens and Pregnancy Antigen strength may decline dramatically during pregnancy.Transiently Le (a-b-) may produce Lewis antibodies during pregnancy.Antigens return after delivery and antibodies disappear.
22 Interaction of Le, Se and H Genes The le, h and se genes are amorphs and produce no detectable products.lele will not have Lewis antigens, but if Se present will have A, B and H in secretionsGenotype se/se and have one Lewis gene will have Lea in their secretions but no A, B or H.
23 Lewis System Le (a+b-) Le (a-b+) Le (a-b-) Lewis Phenotype ABH SecretorLewis SecretorLe (a+b-)All ABH NON-SecretorsAll Lea SecretorsLe (a-b+)All ABH secretorsAll secretors of Lea and LebLe (a-b-)80% ABH secretors20% ABH NON secretorsNONE
24 Lewis Antibodies Naturally occurring, NOT clinically significant Almost always IgMReact most often at RTAgglutination relatively fragile, easily dispersedMay cause ABO discrepancy if reverse cells have Lewis antigen.Occur almost exclusively in Le (a-b-) and production of anti-Lea AND –Leb not unusualAnti-Lea frequently encountered, anti-Leb rarely encountered.
25 Lewis AntibodiesAlthough most react at RT reactivity may be seen at 37C, but is weaker and may be weakly reactive at AHGCan bind complement and cause IN-VITRO hemolysis, most often with enzyme treated cellsAntibodies NOT implicated in HDFN – TWO REASONSAntibodies are IgM andAntigens are poorly developed at birth
26 Lewis AntibodiesCan be neutralized in-vitro by addition of Lewis SubstanceLe antigens are present in secretionsAdd to serum with Lewis antibodies and the antibodies will be bound to the soluble Lewis antigensUseful when multiple antibodies are present and one is a Lewis, eliminates the reactivity of the antibody
27 Lewis Neutralization S1 S2 S3 Original 2+ Le Substance – only Le Ab Row 2 antibody reacting with S1 and S3 which are Lewis positive.Row 2 indicates antibody was neutralized by Lewis substance, no other antibodies present.Row 3 indicates additional antibody present.S1S2S3Original2+Le Substance – only Le AbLe Substance-Le and additional Ab1+
28 Lewis Antibodies - Transfusion Practice Transfused RBCs will acquire the Lewis phenotype of the recipient within a few daysLewis antibodies in patient will be neutralized by Lewis substance in donor plasmaLewis antibodies rarely cause in-vivo hemolysisIt is not necessary to phenotype donors for Lewis antigens prior to transfusion, give crossmatch compatible
29 P Blood Group (ISBT 003) Whites Blacks P1 79% 94% P2 21% 6% Discovered 1927 when Landsteiner immunized rabbits with human RBCsInitially named “P” but as complexity of P blood group was discovered renamed “P1”RBCs lacking P1 are P2Other P phenotypes exist but are rare(<1%): P, P1k and P2kWhitesBlacksP179%94%P221%6%
30 P1Strength of the P1 antigen varies among different RBC samples and antigen strength reported to diminish when RBCs are stored.Characteristics creates difficulties, both in testing RBCs for the antigen and in the identification of the antibody.Anti-P1 blood typing reagents usually sufficiently potent to detect weak forms of the antigen.An antibody that is weakly reactive at RT testing can often be shown to have anti-P1 specificity by lowering the incubation temperature or using enzyme treated RBCs.
31 Anti-P1 The sera of P2 persons commonly contain anti-P1. The antibody reacts optimally at 4 C but may occasionally be detected at 37 C.Rarely may cause in-vitro hemolysis.As it is nearly always IgM, it does not cross the placenta and has not bee reported to cause HDFN (antigen poorly expressed on fetal cells).Anti-P1 little clinical significance unless reactive at 37 C.Anti-P1 has rarely been reported to cause hemolysis in vivo.
32 Neutralization of P1 Antibodies Hydatid cyst fluid or P1 substance derived from pigeon eggs inhibits the activity of anti-P1.Neutralization or inhibition is a useful aid to the identification of anti-P1, especially if the antibody is present in a serum with multiple antibodies.The anti-P1 is neutralized (becomes non-reactive) revealing other specificities (if present).
33 Neutralization of P1 Antibodies Row 1 – original testingRow 2 – antibody successfully neutralized, no underlying antibody.Row 3 – presence of additional antibodyS1 (P1 pos)S2 (P1 neg)S3 (P1 pos)Original2+1+Neutralized
34 Transfusion Practice P Clinically insignificant RT agglutinin.Not necessary to provide antigen negative blood.Must be crossmatch compatible.If reactive at 37C or AHG select crossmatch compatible blood.