Blood Groups & Blood Banking.

Blood Groups & Blood Banking. Godfrey P. MujuziIntroduction to Blood GroupsBlood group is a classification of blood based on the presence or absence of inherited antigenic substances on the surface of red blood cells (RBCs)Antigens may be proteins, carbohydrates, glycoproteins, or glycolipids, depending on the blood group system.Some antigens are present on other cell types, tissues and body fluids.

ctnd Blood groups are inherited and represent contributions from both parents. A total of 30 human blood group systems are now recognized by the International Society of Blood Transfusion (ISBT) .(2008) ABO, Rhesus,MN,P,Lutheran,Kell,Lewis,Duffy, Kidd Hh/Bombay etc.Not all are as medically important as others. ABO Blood Group System(Introduction). Discovered in 1901 by Karl Landsteiner.He observed that red cells of some individuals were agglutinated by serum of other individuals.Classified blood into 4 groups based on which antigen was present on the red cells ( A, B, AB).O = absence of A or B antigen.

Why is it important?ABO compatibility between donor cell and patient serum is the essential foundation of pretransfusion testing.It is the only system with expected antibodies.Whether they are IgG or IgM, ABO antibodies can activate complement readilyThis means that incompatibilities can cause life threatening situations (transfusion reactions)ABO Blood Group System(Introduction ctnd).A person's serum contains ABO antibodies against antigens not present on his/her red cells.

The predictable presence or absence of Anti A or Anti B makes it possible to do both Cell and Serum Grouping.

Blood GroupAntigen (Red Cells)Antibody ( Serum)AAAnti-BBBAnti-AABA+BNoneONoneAnti A+B

ABO Antigens, Genetic & Biochemical Considerations

Genes at separate loci control the occurrence and location of ABO antigensThe Formation of ABO antigens is controlled by H, & ABO genes.

H gene = H and h alleles (h is an amorph)ABO genes = A, B and O alleles.A&B genes expresses themselves dominantly to O gene.O is an amorph, shows no observable changes even in homozygous form.

Formation of ABO Antigens. A precursor Substance (PS) composed of Glucose, Glactose and N-acetylglucosamine is present on red cells. The precursor substance (proteins and lipids) is formed on an oligosaccharide chain. The H gene codes for an enzyme that adds the sugar fucose to the terminal sugar of the precursor substance to form the H Substance/Antigen. The H substance/Antigen is then acted upon by A, B or O genes.

Formation of ABO Antigens.The A gene codes for an enzyme ( N-acetylgalactosaminyltransferase) that adds N-acetylgalactosamine to the terminal sugar of the H antigen/Substance turning it into A antigen.

The B gene codes for an enzyme (D-galactosyltransferase) that adds D-galactose to the terminal sugar of the H antigen turning it into the B antigen.

If the O gene is present, the H substance remains unaltered ( No A or B antigen is formed)Formation of ABO Antigens.The h gene is an amorph = (No gene product). If one inherits hh, the precursor substance can not be converted to H substance/Antigen.Results in the rare Bombay Blood Group Originally found in Bombay (now Mumbai).Bombay blood group ( No A or B antigen, No H substance).Blood group O ( No A or B antigen, Lots of H substance).Blood Groups A, B & AB ( A, B, or AB Antigens present + some H substance)

Bombay!The hh causes NO H antigen to be producedResults in RBCs with no H, A, or B antigen (patient types as O)Bombay RBCs are NOT agglutinated with anti-A, anti-B, or anti-H (no antigens present)Bombay serum has strong anti-A, anti-B and anti-H, agglutinating ALL ABO blood groupsWhat blood ABO blood group would you use to transfuse this patient??RBC Precursor StructureGlucose Galactose N-acetylglucosamineGalactose Precursor Substance (stays the same) RBCFormation of the A antigenGlucose Galactose N-acetylglucosamineGalactose RBCFucoseN-acetylgalactosamineFormation of the B antigenGlucose Galactose N-acetylglucosamineGalactose RBCFucoseGalactoseABO SubgroupsABO subgroups differ in the amount of antigen present on the red blood cell membraneSubgroups have less antigen Subgroups are the result of less effective enzymes. They are not as efficient in converting H antigens to A or B antigens (fewer antigens are present on the RBC)Subgroups of A are more common than subgroups of B15Subgroups of AThe 2 principle subgroups of A are: A1 and A2Both react strongly with reagent anti-ATo distinguish A1 from A2 red cells, the lectin Dolichos biflorus is used (anti-A1)80% of group A or AB individuals are subgroup A120% are A2 and A2BA2 PhenotypeWhy is the A2 phenotype important?A2 and A2B individuals may produce an anti-A1This may cause discrepancies when a crossmatch is done (incompatibility)Whats the difference between the A1 and A2 antigen?Its quantitativeThe A2 gene doesnt convert the H to A very wellThe result is fewer A2 antigen sites compared to the many A1 antigen sites A1 and A2 Subgroups*Anti-A antiseraAnti-A1 antiseraAnti-H lectinABO antibodies in serum# of antigen sites per RBCA14+4+0Anti-B900 x103A24+03+Anti-B & anti-A1250 x103

*Adapted from Flynn, J. (1998). Essentials of ImmunohematologyOther A subgroupsThere are other additional subgroups of AAint (intermediate), A3, Ax, Am, Aend, Ael, Abantu A3 red cells cause mixed field agglutination when polyclonal anti-A or anti-A,B is usedMixed field agglutination appears as small agglutinates with a background of unagglutinated RBCsThey may contain anti-A1B SubgroupsB subgroups occur less than A subgroupsB subgroups are differentiated by the type of reaction with anti-B, anti-A,B, and anti-HB3, Bx, Bm, and Bel ABO AntibodiesThe ABO Blood Group System does NOT require the presence of a foreign red blood cell for the production of ABO antibodiesABO antibodies are non-red blood cell stimulated probably from environmental exposure and are referred to as expected/naturally occurring antibodies

Anti-A1Group O and B individuals contain anti-A in their serumHowever, the anti-A can be separated into different components: anti-A and anti-A1Anti-A1 only agglutinates the A1 antigen, not the A2 antigenThere is no anti-A2. Anti-A,BFound in the serum of group O individualsReacts with A, B, and AB cellsPredominately IgG, with small portions being IgMAnti-A,B is one antibody, it is not a mixture of anti-A and anti-B antibodies ABO antibodiesIgM is the predominant antibody in Group A and Group B individualsAnti-AAnti-BIgG (with some IgM) is the predominant antibody in Group O individualsAnti-A,B (with some anti-A and anti-B)ABO AntibodiesUsually present within the first 3-6 months of lifeStable by ages 5-6 yearsDecline in older ageNewborns may passively acquire maternal antibodies (IgG crosses placenta)Reverse grouping (with serum) should not be performed on newborns or cord blood25Remember: most ABO antibodies are IgM, but some are IgG. Mothers can pass those IgG antibodies through placenta to fetusABO antibodiesNon-red blood cell stimulated (ABO antibodies)Red blood cell stimulatedAntibodies formed as a result of transfusion, etcUsually IgGActive at 37CCan occur in group O (may occur in group A or B)These antibodies also occur in the other Blood Group SystemsRhesus ( Rh)SystemRh system is the second most important system in transfusion medicine after ABO.Antibodies to Rhesus Monkey red cell antigens agglutinate more than 80% of human red cells. An antigen present on some human red cells reacts the to antibodies against the Rhesus antigens the same way as the one on rhesus monkey cells but the antigens are different. Individuals with this antigen are said to be Rhesus positive While those who lack it are Termed Rhesus Negative. Rhesus antigens are only present on Red blood cells.Rh GenesSix (6) genes C, D, E and their allelomorphs: c, e,& d. A chromosome can carry C or c, D or d, E or e but not both. There are eight possible gene combinations i.e. CDe, cDE, cDe, CDE, Cde, cdE, CdE, cde.A person inherits a set of three genes from each of the parents e.g. Cde/CdERh GenesShort hand system used to refer to the Gene combinations.

Rh Antigens (combinations)Short HandCdeR1cDER2cDeR0CDERzCdercdERCdErycderThe D antigenWhen using the Fisher-Race derived nomenclature, Rh antigens bare the sane name as their genes i.e. Antigens D,C,c, E &e.d gene is not expressedD antigen is the most medically import Rh antigen.Weak D antigen (Du ), reduced red cell receptors, reacts less strongly with ant D.

Rh Antibodies.Not present in persons lacking the corresponding antigens.Formed by immunization.Anti D the most medically important.

Blood TransfusionAdministration of blood or its products into ones circulation intravenously.Involves:-Blood donationTesting the blood for suitability Processing blood products Compatibility testing Investigation of Transfusion Reactions.Blood DonationSources of blood for transfusion.Autologous = Donates to self (Donor and recipient the same).Pre-operative HeamodilutionPerioperative salvagePost Operative salvage

Allogenic = Donor and recipient not the same.Voluntary blood donorsDirected donations.( blood donated to a specific individual say relative).Replacement ( Given to replace transfused blood in the bank to ensure continuity of supply)Commercial, highly discouraged.

Donor selection. Donor Safety.Age e.g. 18-65 (national guidelines apply) Hb. ( at least 13.5g/dl male, 12.5 female).Contraindicated conditions. e.g. hyper/hypotension, bleeding/clotting disorders, pregnancy, lactation (first year) etc.Weight, 45kg. Frequency of donations ( at least 90 days interval).Post donation activities.

Donor Selection Recipient SafetyDonor risky behavior ( Medical history, lifestyle, drug abuse. etc)Medical exam (Temp,swollen glands, skin rashes etc)Testing for Transfusion Transmissible Infections.HIV , Hepatitis B &C, Syphilis, Malaria, Human T cell lymphotropic Virus (HTLV) 1 etc.Compatibility testing.

Compatibility TestingMajor aim is to detect any serological incompatibilities that might result in decreased survival of transfused red cells.ABO & Rh Grouping. The cross matchSaline at room temperatureAlbumin eneriched37 degreesThe coombs test