[4] CHAPTER II LESSON 2 Flashcards
2Represents phenotypes that show weaker variable serologic reactivity with the commonly used human polyclonal anti-A, anti-B, and anti-AB reagents.
ABO SUBGROUPS
The weaker serologic reactivity of ABO subgroups is attributed to the decreased number of [?] on their red cells.
A and B antigen sites
In 1911, [?] descried two different A antigens based on reactions between group A RBCs and anti-A and anti-A1.
von Dungern
Cause discrepancies in [?].
ABO testing and cross matches
Group A RBCs that react with both [?] are classified as A1
anti-A and anti-A1
Those that react with [?] and not anti-A1 are classified as A2.
anti-A
Classification into A1 and A2 cells account for [?] of all group A individuals
99%
BLOOD GROUP A1 ANTI-A REAGENT
+
BLOOD GROUP A1 ANTI-A1 LECTIN REAGENT
0
BLOOD GROUP A2 ANTI-A REAGENT
+
BLOOD GROUP A2 ANTI-A1 LECTIN REAGENT
+
Differences in the precursor oligosaccharide chains
↓ Number of antigen sites
Subtle differences in transferase enzymes
↓ Amount of transferase enzyme
Formation of anti-A1, in a percentage of some subgroups
↓ Amount of branching
The immunodominant sugar on both A1 and A2 RBCs is
N-actylD-galactosamine
Differentiation of A1 and A2 phenotypes can be determined by using a reagent made from the seeds of the plant
Dolichos biflorus
is found in greatest concentration on the RBCs of O individuals
H antigen
Reactivity of anti-H antisera or anti-H lectin with ABO blood groups:
O > A2 > B > A2B > A1 > A1B
- agglutinates A1 or A1B
- Dolichos biflorus
agglutinates B cells
- Bandeiraea simplicifolia
- agglutinates O cells (H specificity) and other ABO blood groups depending on the amount of H antigen available
- Ulex europaeus
In accordance with Landsteiner’s rule for expected ABO antibodies, sera from group O and B individuals contain
anti-A antibodies.
The anti-A produced by group O and B individuals can be separated by adsorption and elution techniques into two components:
anti-A and anti-A1
is specific for the A1 antigen and does not agglutinate A2 red cells
Anti-A1
The optimal reactivity of this antibody is at room temperature or lower.
AntiA1
is not considered clinically significant for transfusion purposes
AntiA1
becomes a concern when it causes problems with ABO phenotyping results and incompatible crossmatches on immediate spin
AntiA1
does not exist because the A2 phenotype possesses the same A antigens as A1 phenotype but in reduced quantities.
Anti-A2
Individuals with A1 phenotype do not respond immunologically when exposed to
A2 red cells.
A1 Anti A
4+
A1 Anti A
0
A1 Anti B
4+
A1 AntiA,B
4+
A1 Anti A1
4+
A1 Common
anti-B
A1 Unexpected
None
A1 Subs. Present in the saliva of secretors
A, H
A1 Number of antigen sites RBC x 103
810-1170
A2 Anti A
4+
A2 Anti B
0
A2 AntiA,B
4+
A2 Anti A1
0
A2 Common
anti-B
A2 Unexpected
anti- A1 (1%-8% of cases)
A2 Subs. Present in the saliva of secretors
A, H
A2 Subs. Present in the saliva of secretors
A, H
A2 Number of antigen sites RBC x 103
240-290
Subgroups weaker than [?] occur infrequently and are most often recognized through an ABO discrepancy (unexpected reactions in the forward and reverse grouping).
A2
These subgroups of A make up [?] of those encountered in the laboratory and therefore are mainly of academic interest.
1%
can be utilized to subdivide A individuals into A3, Ax, Aend, etc.
Secretor studies, adsorption-elution tests, and molecular testing
Occasionally, weak subgroups of [?] may present practical problems, for example, if an Ax donor was mistyped as group O and was transfused to a group O patient.
A
This is potentially dangerous because the group O patient possesses [?], which agglutinates and lyses Ax RBCs, causing rapid intravascular hemolysis.
anti-A,B
Characteristics:
1. Decreased number of [?] (resulting in weak or no agglutination with human polyclonal anti-A)
2. Varying degrees of agglutination by [?]
3. Increased variability in the detectability of [?] resulting in strong reactions with anti-H
4. Presence or absence of [?] in the serum
A antigen sites per RBC
human anti-A,B
H antigen
anti-A1
Weak A phenotypes can be serologically differentiated using the following techniques:
1. Forward grouping of [?] with anti-A, anti-A,B and anti-H
2. Reverse grouping of [?] and the presence of [?]
3. Adsorption-elution tests with [?]
4. Saliva studies to detect the presence of [?]
A and H antigens
ABO isoagglutinins; antiA1
anti-A
A and H substances
Additional special procedures such as [?] for detecting the A enzyme that can be performed for the differentiation of weak subgroups.
molecular testing, serum glycosyltransferase studies
Absence of a disease process should be confirmed before subgroup investigation because [?] are altered in various malignancies and other hematologic disorders.
ABH antigens
Weak A subgroups can be distinguished as:
Characteristically demonstrate a mixed field pattern of agglutination with anti-A and anti-A,B reagents.
A3 RBCs
The estimated number of A antigen sites is approximately 35,000 per RBC.
A3 RBCs
Weak a-3-N-acetylgalactosamine activity is detectable in the serum.
A3 RBCs
Anti-A1 may be present in serum of A3 individuals, and A substance is detected in the saliva of A3 secretors.
A3 RBCs
Characteristically not agglutinated by anti-A reagent but do agglutinate with most examples of anti-A,B
Ax RBCs
Characteristically not agglutinated by anti-A reagent but do agglutinate with most examples of anti-A,B
Ax RBCs
Estimated number of A antigen sites is approximately 4,000 per RBC
Ax RBCs
Anti-A can be adsorbed and then eluted from Ax cells without difficulty.
Ax RBCs
Transferase: not detectable in the serum or in the RBC membranes of Ax individuals
Ax RBCs
individuals almost always produce anti-A1 in their serum
Ax RBCs
Routine secretor studies detect the presence of only H substance in Ax secretors
Ax RBCs
contain A substance detectable only by agglutination/ inhibition studies using Ax RBCs as indicators
Ax RBCs
Caution should be used in interpreting results of secretor studies using Ax indicator cells and anti-A, because not all Ax cells are agglutinated by anti-A.
Ax RBCs
Characteristically demonstrate mixed-field agglutination with antiA and anti-A, B, but only a very small percentage of the RBCs (10% or less) agglutinate.
Estimated number of A antigen sites on the few agglutinable RBCs is approximately 3500 per RBC, whereas no detectable A antigens are demonstrated on RBCs that do not agglutinate.
Secretor studies detect the presence of only H substance in the saliva of Aend secretors. AntiA1 is found in some Aend sera.
Aend RBCs
The phenotypes of Afinn and Abantu are considered by some investigators to represent variants of the Aend subgroup
Aend RBCs
