Blood Bank Chapter 5

How are blood systems grouped?

• ABO system was the first blood group system described and still remains the most important blood group system for transfusion purposes

• Composed of antigens that are produced by alleles at a single genetic locus (locations) or at loci that are linked so closely that genetic crossing over may occur

Identify the primary location of blood group antigens

• Genetic locus or loci

List two ways that blood group antigens can be introduced in order to stimulate an immune response

• Transfusion

• Pregnancy

Identify the function of ISBT

• Standardizes blood group systems and antigen names with the working party on terminology for Red Cell Antigens

Discuss the history of ABO blood groups and the formation of Landsteiner’s rule

• Standardized blood group systems and antigen names with the working party

List five manifestations and three complications associated with transfusing ABO incompatible blood

• Complications:

  • Irreversible shock

  • Renal failure

  • DIC

• Manifestations:

  • Intravascular hemolysis

  • Rapid onset of fever

  • Chills

  • Hemoglobinemia

  • Hypotension

Identify the common structure for A, B, and H antigens

• Oligosaccharide Chain

Identify six locations that ABO and H antigens may be found

• Red cells

• Lymphocytes

• Platelets

• Most endo- and epithelial cells

• Organs like kidneys

State the body fluids that ABO and H antigens can be found in

• Secretions

• All body fluids except CSF

Identify the age at which ABO and H antigens can be fully formed

• 2-4 years old

Identify the immunodominant sugar for the A, B, and H antigens

• H: L-fucose

• A & B: N-Acetylgalactosamine & D-Galactose

Explain the Bombay phenotype and the cause for it

• Individuals with H allele are classified as Bombay phenotype. They lack H and its subsequent ABO expression on their red cells

State the manifestation of Bombay phenotype as it will be seen in blood bank

• Patients type as O, but crossmatches will be incompatible due to their antibodies against the A, B, and H antigens

Identify the allele that has the greatest concentration and least concentration of H antigen

• Greatest concentration of H antigen: O Allele

• Least concentration of H antigen: A1B cells

List the lectins used for ABO and H testing

• Dolichos biflorus

• Ulex europaeus

State the importance of the Se gene and correlate it with secretor status

• Soluble ABO antigens are found in saliva, urine, tears, bile, amniotic fluid, breast milk, exudate (fluid that filters from the circulatory system into lesions or areas of inflammation), and digestive fluids

• 80% of population are secretors

Identify five body fluids that ABO antigens can be found in secretors

• Saliva

• Urine

• Tears

• Bile

• Amniotic fluid

• Breast milk

• Exudate

State how ABO subgroups differ from the primary group

• Differ in the amount of antigen expressed on the red cell membrane, resulting in a different number of antigen sites

Identify the predominant subgroup of A

• A2

Correlate reagent reactions as they differentiate A1 and A2

• May demonstrate weak or no agglutination with anti-A reagents due to decreased number of antigen sites, but will usually have stronger reaction with anti-A,B

List three subgroups of A other than A2

• A3

• Ax

• Ael

Recognize the subgroup of A

• Some subgroups demonstrate mixed field (mf) agglutination; Ex: A3

Describe testing procedures for subgroups of A

• Despite its formulation, some subgroups of A continue to not react or react poorly with murine monoclonal blends of anti-A

Explain the significance of identifying ABO subgroups

• Weak or no reaction of red cells of blood donor may result in mistyping of blood, which can cause a transfusion reaction when given to an incompatible recipient

Correlate ABO phenotypes with genotypes

• Red cells can only be phenotyped. Familial studies are required for genotyping

Explain theory of ABO antibodies

• It is thought that biochemical structures that are similar to A and B antigens are present in environmental substances like pollen, plants, and bacteria

Discuss how ABO antibody titers relate to age

• Ab not detected in newborns until 3-6 months of age

• Maximum titers in children 5-10 years old

• Titers decrease with advanced age

Correlate decreased antibody titers with pathological conditions

• Newborn

• Elderly

• Chronic lymphocytic leukemia

• Multiple Myeloma

• Bone marrow transplant

• Immunosuppressive therapy

• Hypo- or agammaglobulinemias

Identify the antibody class and clinical significance of anti-A and anti-B

• Ab capable of causing decreased surbibal or red cells in a transqusion or capable of causing HDN

Discuss the uses of anti-A,B 

a.      Cross-reactive with both A and B antigens

b.     Can detect subgroups of A and B

c.      Used most often in ABO discrepancies and confirming ABO of group O donor red cells

d.     ABO Ab react at -25 C without incubation or potentiators and immediately after centrifugation

Explain how to select red cell units based on phenotype and red cell availability

• The first choice is ABO identical units, in which the phenotype of both the donor and the recipient are the same

Discuss three ways that ABO discrepancies are initially manifested in blood bank

a.      Anti-A1?

b.     Cold auto-or alloantibodies?

c.      Rouleaux?

List four ABO discrepancies associated with the appearance of extra ABO antigens

a.      Acquired B phenotype

b.     B (A) Phenotype

c.      Polyagglutination

d.     Rouleaux

e.     Hematopoietic Progenitor cell

f.        Transplants

List two ABO discrepancies associated with the appearance of missing or weak ABO antigens

a.      ABO subgroup

b. Pathologic Etiology

List three causes of mixed field reactions in ABO discrepancies

a.      Transfusion of group O to A, B or AB

b.     Bone marrow or Hematopoietic progenitor stem cell transplants

c.      A3 phenotype

List three causes of extra antibodies in ABO discrepancies

a.      A subgroups with anti-A1

b.     Cold antibodies (allo- or auto-)

c.      Rouleaux

List three causes of missing or weak antibodies in ABO discrepancies

a.      Newborn

b.     Elderly

c.      Pathologic Etiology; Ex: Agammaglobulinemia

Discuss the three major technical errors associated with ABO discrepancies and ways to prevent them

a.      Identification or Documentation Errors

b.     Reagent or Equipment Errors

c.      Standard Operating Procedure Errors

Explain how to resolve ABO discrepancies as they relate to technical errors

  i.      Obtain a new sample to eliminate possible contamination or identification problems

ii.      Wash red cells to remove extra protein or autoantibodies

iii.      Once the technical error is resolved, repeat testing. If discrepancy is still present, a discrepancy with the sample may be present

Discuss the cause of reactions associated with and resolution of acquired B phenotype

• Most common reason for this discrepancy is a bacterial deacetylating enzyme that alters the A immunodominant sugar by removing the acetyl group. The resulting sugar resembles the B immunodominant sugar, and cross-reacts with many anti-B reagents

Discuss the cause of reactions associated with and resolution of B (A) phenotype

• Results from an increased  sensitivity of monoclonal antibody reagents. The B gene transfers trace amounts of the A immunodominant sugar and the B immunodominant sugar to the H antigen acceptor molecules. The trace amounts of A antigens are detected wit some clones of monoclonal antibody

Discuss the cause of reactions associated with and resolution of Subgroup of A

• Additional testing with anti-A,B yields a 1+ result in the patient’s red cells, which is indicative of a subgroup of A; Further testing may include A2 cells, A1 lectin, and adsorption and elution with anti-A

Discuss the cause of reactions associated with and resolution of Mixed field reactions

• Due to the presence of two distinct cell populations as will occur in the transfusion of ABO compatible (not identical) red cells, bone marrow recipients, stem cell transplant, individuals with A3 phenotype, and patients with Tn-polyagglutinable red cells (polyagglutination that results from a mutation in hematopoietic tissue)

Discuss the cause of reactions associated with and resolution of cold antibodies

• Donors and patients may possess antibodies to red cell antigens other than those of the ABO blood group. They can have the following specificities: Anti-P1, Anti-M, Anti-N, Anti-Lea, and Anti-Leb. (Known collectively as cold antibodies because they react at or below room temperature)

Discuss the cause of reactions associated with and resolution of Rouleaux

• Due to increased concentrations of serum proteins, cells can form agglutination in a manner that resembles stacked coins; Associated with multiple myeloma or Waldenstrom’s macroglobulinemia (overproduction of IgM by clones of plasma B cells in response to antigenic stimulation)

Discuss the cause of reactions associated with and resolution of Missing or weak antibodies

• ABO subgroups; Weakened antigen expression due to leukemia or Hodgkin’s disease

Discuss the mini cold panel

a.      No longer routinely performed

b.     Usually uses group O cord blood samples since cord blood cells are I negative, though some manufacturers supply this as a reagent

c.      Uses cells that will specifically identify cold antibodies

Explain the procedure of saline replacement

a.      Incubate test serum/plasma and red blood cells, then centrifuge, and remove serum/plasma from tube with a pipet

b.     Replace serum with an equal amount of saline

c.      Centrifuge for 15 seconds and resuspend the cell button

d.     No agglutination= Rouleaux

Stated that normal healthy individuals possess ABO antibodies to the ABO red cell antigens that are lacking on their red cells

• Landsteiner’s rule

Uses red cells (known antigens) to remove red cell antibodies from patient plasma or serum

• Adsorption

Dissociates immune complexes on red cells; freed antibody is then tested for specificity

• Elution

The phenotype of both the donor and the recipient are the same

• ABO identical

Though the ABO groups between the donor and the recipient are not identically the same, they can be safely transfused into the recipient without causing a transfusion reaction

• ABO compatible

Donor group that can be safely transfused to all other ABO groups. For red cells-Group O. For plasma-Group AB

• Universal donor

Donor group that can safely receive units from all other ABO groups. For red cells-Group AB. For plasma- Group O

Universal recipient

Agglutination of red cells by most human sera despite blood type due to hidden T antigen on red cells from a bacterial infection

• Polyagglutination

Gelatinous tissue contaminant in cord blood samples that causes nonspecific aggregation

• Whartons’ jelly