Blood transfusion

Blood Group Antigens and Antibodies

• The study of red blood cell (RBC) antigens and antibodies forms the foundation of transfusion medicine.

• Antigens, either carbohydrate or protein, are assigned to a blood group system based on the structure and similarity of the determinant epitopes.

alloimmunization

• production of antibodies against the blood group antigens of another individual.

• antibodies are called alloantibodies.• Alloimmunization to leukocytes, platelets,

and plasma proteins may also result in transfusion complications such as fevers and urticaria but generally does not cause hemolysis.

Ig M antibodies• occur via natural stimuli • produced by a T cell–independent

response (generating no memory).• Autoantibodies arise spontaneously or as

a result of infectious sequelae (M.pneumoniae) & are IgM.

• clinically insignificant due to their low affinity for antigen at body temperature.

• activate complement cascade hemolysis

Ig G antibodies

• allogeneic exposure, such as transfusion or pregnancy.

• bind to antigen at warmer temperatures and may hemolyze RBCs.

• can cross placenta & bind fetal RBCs causing hemolytic disease of the newborn, or hydrops fetalis.

ABO Antigens and Antibodies

• recognized in 1900 • major blood groups are A, B, AB,

and O.• These antigens are carbohydrates

attached to a precursor backbone, found on cell membrane as glycosphingolipids or glycoproteins, & secreted in plasma & body fluids as glycoproteins.

Karl Landsteiner

• H substance - immediate precursor on which A & B Ag

are added - formed by addition of fucose to glycolipid

or glycoprotein backbone.• subsequent addition of - N-acetylgalactosamine A antigen - galactose B antigen.

ABO blood group system: diagram showing the carbohydrate chains that determine the ABO blood group

• A & B phenotypic genes are found on chromosome 9p

• Mendelian codominant • gene products are glycosyl transferases, which

confer the enzymatic capability of attaching the specific antigenic carbohydrate.

• A & B transferases absent in O & inherited in AB

• individuals lacking H gene (codes for fucose transferase) are homozygous for the silent h allele (hh) & have Bombay phenotype (Oh).

Phenotype Genotype

A AA or AO

B BB or BO

AB AB

O OO

• naturally occurring anti-A and anti-B antibodies are termed isoagglutinins.

• O – universal donor• AB - universal recipient• Bombay phenotype produce antibodies to H

substance (which is present on all red cells except those of hh phenotype) as well as to both A and B antigens and are therefore compatible only with other hh donors.

RBC Compatibility chartIn addition to donating to the same blood group; type O blood donors can give to A, B and AB; blood donors of types A and B can give to AB.

• A & B Ag are secreted by the cells & are present in circulation.

• Nonsecretors are susceptible to variety of infections (eg. C.albicans, N.meningitidis, S.pneumoniae, H.influenzae) as many organisms may bind to polysaccharides on cells.

• Soluble blood group antigens may block this binding.

Rh System • 2nd most important blood group system in

pretransfusion testing.• Rh Ag are found on 30- to 32-kDa RBC

membrane protein that has no defined function.

• >40 different Ag in Rh system have been described

• five determinants account for the vast majority of phenotypes.

• presence of the D Ag confers Rh "positivity”

• Two allelic Ag pairs, E/e and C/c, are also found on the Rh protein.

• three Rh genes, E/e, D, and C/c, are arranged in tandem on chromosome 1 and inherited as a haplotype, i.e., cDE or Cde. Two haplotypes can result in the phenotypic expression of two to five Rh antigens.

• The D antigen is a potent alloantigen. • About 15% of individuals lack this antigen. • Exposure of these Rh-negative people to

even small amounts of Rh-positive cells, by either transfusion or pregnancy, can result in the production of anti-D alloantibody.

Red blood cell compatibility table

Recepient DonorO- O+ A- A+ B- B+ AB- AB+

O-O+A-A+B-B+AB-AB+

Other Blood Group Systems and Alloantibodies

• More than 100 blood group systems are recognized, composed of more than 500 antigens.

• The presence or absence of certain antigens has been associated with various diseases and anomalies; antigens also act as receptors for infectious agents.

RBC Blood Group Systems and Alloantigens

Blood Group System

Antigen Alloantibody Clinical Significance

Rh (D, C/c, E/e) RBC protein IgG HTR, HDN

Lewis (Lea, Leb) Oligosaccharide IgM / IgG Rare HTR

Kell (K/k) RBC protein IgG HTR, HDN

Duffy (Fya/Fyb) RBC protein IgG HTR, HDN

Kidd (Jka/Jkb) RBC protein IgG HTR (often delayed), HDN (mild)

I/I Carbohydrate IgM None

MNSsU RBC protein IgM / IgG Anti-M rare HDN, anti-S, -s, and -U HDN, HTR

• Lewis system:• most common cause of incompatibility during

pretransfusion screening. • Lewis gene product is a fucosyl transferase and

maps to chromosome 19. • antigen is not an integral membrane structure

but is adsorbed to the RBC membrane from the plasma.

• Antibodies to Lewis antigens are usually IgM.• Lewis antigens may be adsorbed onto tumor

cells and may be targets of therapy.

• I system:• antigens are oligosaccharides related to H, A, B, and Le.• I and i are not allelic pairs but are carbohydrate antigens

that differ only in the extent of branching. - i antigen : unbranched chain : converted by the I gene product, a glycosyltransferase,

into a branched chain : branching process affects all the ABH antigens, which

become progressively more branched in the first 2 years of life.• Most adults lack i expression; & express I antigen• I Ag binding is generally low at body temperature.

administration of warm blood prevents isoagglutination.

• P system:• group of carbohydrate antigens controlled by specific

glycosyltransferases.• clinical significance:

- rare cases of syphilis & viral infection that lead to paroxysmal cold hemoglobinuria.

- In these cases, an unusual autoantibody to P is produced that binds to RBCs in the cold and fixes complement upon warming.

- Antibodies with these biphasic properties are called Donath-Landsteiner antibodies.

• P antigen is cellular receptor of parvovirus B19 and also for E.coli binding to urothelial cells.

• MNSsU system:• genes on chromosome 4.• M & N: determinants on glycophorin A, an RBC

membrane protein S & s: determinants on glycophorin B. • Anti-S & anti-s IgG antibodies may develop after

pregnancy or transfusion and lead to hemolysis.• Anti-U antibodies are rare but incompatible as

nearly all persons express U.

• Kell protein • very large (720 AA); many different antigenic epitopes. • immunogenicity of Kell is 3rd after ABO and Rh systems.• gene on X chromosome• absence of the Kell precursor protein:

- acanthocytosis, - shortened RBC survival, - progressive form of muscular dystrophy including cardiac

defects. - This rare condition is called the McLeod phenotype.

• Kx gene :– linked to the 91-kDa component of NADPH-oxidase on the X – deletion or mutation: chronic granulomatous disease.

• Duffy:• antigens are codominant alleles: Fya, Fyb • receptors for Plasmodium vivax.• >70% individuals in malaria-endemic

areas lack these antigens, probably from selective influences of the infection on the population

• Kidd :• Antigens: Jka and Jkb• may elicit antibodies transiently.• delayed hemolytic transfusion reaction:

– occurs with blood tested as compatible – due to delayed appearance of anti-Jka.

Pretransfusion testing

• Pretransfusion testing of a potential recipient consists of the "type and screen”.

• Forward type - determines the ABO and Rh phenotype of the recipient's RBC by using antisera directed against the A, B, and D antigens.

• Reverse type - detects isoagglutinins in the patient's serum

World War II syringe for direct inter-human blood transfusion

• The first historical attempt at blood transfusion was described by the 17th century chronicler Stefano Infessura.

• The first fully documented human blood transfusion was administered by Dr. Jean-Baptiste Denys, eminent physician to King Louis XIV of France, on June 15, 1667.[2] He transfused the blood of a sheep into a 15-year old boy, who survived the transfusion.[3] Denys performed another transfusion into a labourer, who also survived. Both instances were likely due to the small amount of blood that was actually transfused into these people. This allowed them to withstand the allergic reaction.

Blood Components

• Whole Blood• Packed Red Blood Cells • Platelets• Fresh-Frozen Plasma • Cryoprecipitate• Plasma Derivatives

Whole Blood

• Provides: oxygen-carrying capacity & volume expansion. • ideal for: acute hemorrhage of 25% total blood vol. loss • stored at 4°C

– maintains erythrocyte viability– platelet dysfunction, degradation of some coagulation factors

occurs. – 2,3-bisphosphoglycerate levels falls over time, leading to : .. increase in the oxygen affinity of the hemoglobin .. decreased capacity to deliver oxygen to the tissues

• not readily available since it is routinely processed into components.

Packed Red Blood Cells

• ↑es oxygen-carrying capacity in anemia• Adequate oxygenation can be maintained

with a hemoglobin content of :– 70 g/L: in normovolemic patient without cardiac

disease– 100 g/L: in patients requiring transfusion

• decision to transfuse should be guided by the clinical situation and not by an arbitrary laboratory value.

Cont..

• universal prestorage leukocyte reduction– contain <5 x 106 donor WBCs – lowers the incidence of posttransfusion fever,

CMV infections, and alloimmunization• Prestorage filtration • Other benefits: less immunosuppression in

recipient and lower risk of infections. • Plasma (cause allergic reactions) removed

from cellular components by washing.

• Mortality Rates are Lower When Leukocyte Reduced Blood Is Used

Platelets

• reduces the incidence of bleeding.• threshold for prophylactic platelet

transfusion is 10,000/L.– without fever or infections: 5000/L – invasive procedures: 50,000/L is target level.

• given as: pools prepared from 5-8 RDs or as SDAPs from a single donor– each unit ↑ the platelet count 5000–10,000/L.

Cont..

• Apheresis technology is used for the collection of multiple units of platelets from a single donor.

• single-donor apheresis platelets (SDAP): - contain equivalent of at least six units of

RD platelets - have fewer contaminating leukocytes

than pooled RD platelets.

Cont..

• unsensitized patient without increased platelet consumption:

6-8 units of RD platelets (1 unit /10 kg body wt.)

• received multiple transfusions may be alloimmunized :

little or no ↑ in posttransfusion platelet counts.• require multiple transfusions: SDAP & leukocyte-reduced components

Cont..

• platelet count after transfusion1h - CCI 10 x 109/mL, acceptable18–24 h - increment of 7.5 x 109/mL is expected

• Refractoriness can be investigated by detecting anti-HLA antibodies in the recipient's serum

• ABO-identical HLA-matched SDAPs provide the best chance for increasing the platelet count

Fresh-Frozen Plasma• contains stable coagulation factors and

plasma proteins: fibrinogen, antithrombin, albumin, as well as proteins C and S

• Indications:- correction of coagulopathies, including rapid reversal of warfarin- supplying deficient plasma proteins- thrombotic thrombocytopenic purpura

• acellular component• does not transmit intracellular infections

(eg. CMV)• collected by apheresis.

Cryoprecipitate

• source of fibrinogen, factor VIII, and von Willebrand factor (vWF).

• ideal for supplying fibrinogen to the volume-sensitive patient.

• each unit contains 80 units of factor VIII. • vWF : for dysfunctional (type II) or absent

(type III) von Willebrand disease.

Plasma Derivatives

• Plasma may be pooled to derive:- specific protein concentrates: albumin, iv. immunoglobulin, antithrombin, and coagulation factors.- hyperimmune globulins, such as anti-D (RhoGam, WinRho), - antisera to HBV, varicella-zoster virus, CMV, and other infectious agents.

Plasma compatibility chartIn addition to donating to the same blood group; plasma from type AB can be given to A, B and O; plasma from types A and B can be given to O.

•

Examples Of Blood Use Average # Of Units Required

Automobile Accident 50 units of blood

Heart Surgery 6 units of blood6 units of platelets

Organ Transplant 40 units of blood30 units of platelets20 bags of cryoprecipitate25 units of fresh frozen plasma

Bone Marrow Transplant 120 units of platelets20 units of blood

Burn 20 units of platelets

FREQUENCY OF WHITE BLOOD CELL

ASSOCIATED ADVERSE TRANSFUSION

REACTIONS

Red Cells0.5 - 6%

Platelets 20% - 30%

Adverse Reactions to Blood Transfusion

• Immune-Mediated Reactions • Nonimmunologic Reactions• Infectious Complications

Immune-Mediated Reactions • Acute Hemolytic Transfusion Reactions • Delayed Hemolytic and Serologic Transfusion

Reactions• Febrile Nonhemolytic Transfusion Reaction • Allergic Reactions • Anaphylactic Reaction • Graft-versus-Host Disease • Transfusion-Related Acute Lung Injury • Posttransfusion Purpura • Alloimmunization

Acute Hemolytic Transfusion Reactions

• occurs when the recipient has preformed antibodies that lyse donor erythrocytes, mainly ABO isoagglutinins

• Monitoring the patient's vital signs before and during the transfusion is important

• Errors at patient's bedside:– mislabeling the sample– transfusing the wrong patient, are

responsible for the majority of these reactions

• When acute hemolysis is suspected– transfusion must be stopped immediately – intravenous access maintained– reaction reported to the blood bank– posttransfusion blood sample and any

untransfused blood should be sent to the blood bank for analysis

• Diuresis induced with iv. fluids and furosemide or mannitol.

• Tissue factor released from the lysed erythrocytes may initiate DIC.

• evaluation for hemolysis includes: - serum haptoglobin, lactate dehydrogenase

(LDH), and indirect bilirubin levels. • Coagulation studies:

- PT, aPTT, fibrinogen, and platelet count

• blood bank investigation:– examination of pre- and posttransfusion

samples for hemolysis – repeat typing of patient samples– direct antiglobulin test (DAT), called the direct

Coombs test, of the posttransfusion sample– Repeat cross-matching of blood component – checking all clerical records for errors

Delayed Hemolytic and Serologic Transfusion Reactions

• not completely preventable • occur in patients previously sensitized to RBC

alloantigens who have a negative alloantibody screen due to low antibody levels.

• anamnestic response results in early production of alloantibody that binds donor RBCs.

• alloantibody is detectable 1–2 weeks following transfusion

• posttransfusion DAT may be positive • transfused, alloantibody-coated RBCs are

cleared by reticuloendothelial system.• detected mostly in blood bank when a

subsequent patient sample reveals a positive alloantibody screen or a new alloantibody in a recently transfused recipient.

• No specific therapy is required, additional RBC transfusions may be necessary

Febrile Nonhemolytic Transfusion Reaction

• most frequent reaction associated with transfusion of cellular blood components

• chills & rigors and 1°C rise in temperature • diagnosed when other causes of fever in

transfused patient are ruled out. • mild nature

• Antibodies directed against donor leukocyte and HLA antigens may mediate these reactions

• Prevention: - leukoreduction before storage - premedicating with acetaminophen or

other antipyretic agents.

Anaphylactic Reaction• severe reaction • presents after transfusion of only a few milliliters

of blood component • Symptoms and signs :

– difficulty breathing– coughing– nausea and vomiting– hypotension– bronchospasm– loss of consciousness– respiratory arrest– shock.

• Treatment – stop transfusion– maintain vascular access– epinephrine (0.5–1.0 mL, 1:1000, s.c). – Glucocorticoids in severe cases.

• test for IgA deficiency.

Graft-versus-Host Disease • Due to allogeneic stem cell transplantation• lymphocytes from donor attack and cannot be

eliminated by an immunodeficient host.• donor T lymphocytes that recognize host HLA

antigens as foreign immune response• occur when blood components with viable T lymphocytes

are transfused to immunodeficient recipients or to immunocompetent recipients who share HLA antigens with donor (eg. family donor)

• Clinical manifestations appear at 8–10 days• death occurs at 3–4 weeks posttransfusion. • characterized by :

– fever– cutaneous eruption– diarrhea– liver function abnormalities– marrow aplasia and pancytopenia

• highly resistant to treatment with immunosuppressive therapies, including glucocorticoids, cyclosporine, antithymocyte globulin, and ablative therapy followed by allogeneic bone marrow transplantation

Transfusion-Related Acute Lung Injury

• results from transfusion of donor plasma that contains high-titer anti-HLA antibodies that bind recipient leukocytes.

• leukocytes aggregate in pulmonary vasculature and release mediators that increase capillary permeability.

• symptoms of respiratory compromise signs of: - noncardiogenic pulmonary edema - bilateral interstitial infiltrates on chest x-ray. • Treatment – supportive• recover without sequelae• Test donor's plasma for anti-HLA antibodies • implicated donors -often multiparous women

Posttransfusion Purpura

• presents as thrombocytopenia• 7–10 days after platelet transfusion • predominantly in women.• Platelet-specific antibodies found in serum• antigen: HPA-1a (on platelet glycoprotein

IIIa receptor)

• delayed thrombocytopenia due to production of antibodies that react to both donor and recipient platelets.

• Additional platelet transfusions can worsen the thrombocytopenia and should be avoided.

• Treatment: - iv. immunoglobulin to neutralize effector

antibodies - plasmapheresis to remove antibodies

Alloimmunization

• recipient may become alloimmunized to a number of antigens on cellular blood elements and plasma proteins.

• Alloantibodies to RBC antigens are detected during pretransfusion testing

• sensitized childbearing women:– risk for bearing a fetus with hemolytic disease

of the newborn.

• Matching for D antigen is the only pretransfusion selection test to prevent RBC alloimmunization.

• Alloimmunization to antigens on leukocytes and platelets: - result in refractoriness to platelet transfusions.

• Use:– leukocyte-reduced cellular components– SDAPs.

Nonimmunologic Reactions• Fluid Overload• Hypothermia • Electrolyte Toxicity• Iron Overload• Hypotensive Reactions• Immunomodulation

Fluid Overload

• Blood components are excellent volume expanders

• Monitoring the rate and volume of the transfusion

• Use of diuretic.

Hypothermia

• Refrigerated (4°C) or frozen (–18°C or below) blood components:

- cause hypothermia when rapidly infused• Cardiac dysrhythmias : - exposing the sinoatrial node to cold fluid. • Use of an in-line warmer for prevention

Electrolyte Toxicity

• storage increases the concentration of potassium – Neonates and patients in renal failure are at

risk for hyperkalemia.• use fresh or washed RBCs for prevention• Citrate chelates Ca++

- hypocalcemia may result in from multiple rapid transfusions

Iron Overload• Each unit of RBCs contains 200–250 mg of

iron.• iron overload affecting endocrine, hepatic,

and cardiac function - after 100 units of RBCs have been transfused (total-body iron load of 20 g).

• Use - alternative therapies (erythropoietin) - judicious transfusion - Deferoxamine,other chelating agents

Hypotensive Reactions

• Transient hypotension who take ACE inhibitors.– blood products contain bradykinin that is

normally degraded by ACE– patients on ACE inhibitors may have

increased bradykinin levels that cause hypotension.

– blood pressure typically returns to normal without intervention.

Immunomodulation

• Transfusion of allogeneic blood is immunosuppressive.

• Multiply transfused renal transplant recipients are less likely to reject the graft, and transfusion may result in poorer outcomes in cancer patients and increase the risk of infections.

• mediated by transfused leukocytes. • Leukocyte-depleted cellular products may cause

less immunosuppression.

Infectious Complications • Viral Infections - Hepatitis C Virus - HIV type1 - Hepatitis B Virus - others- HAV, TTV, SEN-V, & GBV-C - West Nile Virus - Cytomegalovirus - HTLV type1 - Parvovirus B-19• Bacterial Contamination • Other Infectious agents - parasites