IMMUNOHEMATOLOGY

• ABO antigens

  • Glycosphingolipids or glycoproteins
  • Histoblood group antigens
  • controlled by ABO genes located at chromosome number 9
  • Not fully developed at birth
• A

  increase risk of gastric CA
• B

  risk of duodenal ulcer
• O

  It was called group C before, universal donor
• H gene

  chromosome 19
• ABO genes

  chromosome 9
• Precursor type 1

  1 – 3 linkage (found in the secretions) glycoprotein
• Precursor type 2

  1 - 4 linkage (present in RC membrane) glycolipids
• H

  L-fucose
• A

  N-acetyl-D-galactosamine
• B

  D-galactose
• foundation of A and B antigens in the RBC and secretions

  H gene
• order of H antigen

  :O>A2>B>A2B>A1>A1
• Se gene

  responsible for the expression of H antigens on glycoprotein(PS type 1)
• Anti-H lectin use to confirm the presence or absence of H antigen

  Ulex europaeus
• A lectin

  Dolichos biflorus
• B lectins

  Bandeiraea simplicifolia
• O lectin

  Ulex europeus
• Lectins - animals, viruses or microorganisms plant extracts that agglutinates human red cells with some degree of specificity
• frequency:

  A1- 80

  A2- less than 20
• A2 and A2B individuals may produce Anti-A1 and may cause discrepancy during crossmatching
• ABO antibodies

  • Reacts best at room temperature
  • predominantly IgM
  • Produces hemolysis in-vivo or in-vitro
  • Naturally occurring antibodies, usually present within 5-6 months of life
• Only forward typing is done for newborns
• Negative (0) No clumps or aggregates

  Weak (+/-) Tiny clumps or aggregates barely visible macroscopically or to the naked eye

  1+ Few small aggregates visible macroscopically

  2+ Medium-sized aggregates

  3+ Several large aggregates

  4+ One solid aggregate
• Methods for determining ABO blood group

  1. Slide method 2. Tube method 3. Gel Card method 4. Microplate method
• Group 1

  Unexpected missing reactions in reverse grouping due to weakly reacting or missing antibodies.
• Group 1

  1. Newborns
  2. Elderly patients
  3. Patients w/ Leukemia or lymphoma
  4. Patients using immunosuppressive drugs
  5. Bone Marrow Transplant Patient
  6. ABO Ab diluted by plasma transfusion
• Resolution

  1. Determine patients age, diagnosis
  2. Incubate serum testing for 15 minutes (RT) to enhance antibody reactions
  3. If negative, place serum testing at 4°C for 15-30 minutes with autologous control (a.k.a. Autocontrol, AC) This is called a “mini-cold” panel and should enhance the reactivity of the antibodies
• Group 2

  Unexpected missing reactions in the forward grouping due to weakly reacting or missing antigen.
• Group 2

  1. Subgroups of A(B) may be present
  2. Leukemias may yield weakened A or B antigen
  3. Hodgkin's disease
  4. Acquired B = pseudo type B
• acquired group B phenomenon (in vivo)

  • Patients with bacterial infections
  • cancer of the colon or rectum may develop false B-like antigen.
• Acquired phenomenon (in vitro)

  blood specimens can get an acquired B-like antigen if they are bacterially contaminated.
• Rare group 2 discrepancy

  BGSS(blood group specific soluble substances) = Anti-sera is being neutralize if there is an excess BGSS and causes false negative result in forward typing.
• presence of two cell population (mf reaction)

  chimerism
• Group 3

  Unexpected additional reactions in the forward and reverse grouping due to plasma protein/ antibody and results in rouleaux formation or pseduoagglutination
• Group 3

  • Elevated levels of globulin from diseases
  • Multiple myeloma
  • Waldenstrom
  • advance case of hodgkins lymphoma
  • Increased fibrinogen
  • Plasma expanders
  • Wharton's jelly- found in cord blood cells
• Resolution for Group 3

  Wash the red cells -If the reverse grouping is affected, perform saline replacement technique (more common)
• Group 4

  Discrepancies between forward and reverse grouping due to miscellaneous problems.
• Group 4

  Cold Antibodies

  • Unexpected Alloantibodies (non-ABO)
  • Autoantibodies = Cold reacting autoantibodies cause agglutination with red cells at RT and below. Note: Autocontrol will be positive

  Resolution: warming tube to 37° and washing red cells can disperse agglutination; breaking the IgM bonds
• Principles of the Antiglobulin test

  1. Antibody molecules and complement components are globulins.2. Injecting an animal with human globulin stimulates the animal to produce antibody to the foreign protein (i.e. AHG)3. Human globulin will be agglutinated by AHG4. Washed RBCs coated with human globulin are agglutinated by AHG