Text Notes

Question 1

Macrophage Sources

Answer 1

Kupffer cells in liver, CT histocytes, and fixed cells within the Reticuloendothelial system

Question 2

Opsonized

Answer 2

Cells targeted because they are coated with antibody or activated complement

Question 3

Fc Receptor

Answer 3

Non-specific cell surface receptors for antibodies bound to antigen that Macrophages bind to

Question 4

What percent of peripheral blood lymphocytes are T cells?

Answer 4

70-80%

Question 5

Immunogen

Answer 5

Is a substance that causes a detectable immune response

Question 6

Antigen

Answer 6

Is a substance that is capable of reacting with the product of an immune response

Question 7

Hapten

Answer 7

A larger carrier molecule that attaches to immunogens that can become immunogenic

Question 8

Difference between “Antibody” and “Immunoglobulin”

Answer 8

Antibody: If the binding specificity is known
Immunoglobulin: A collection of different antibodies with no single binding specificity

Question 9

Hybridomas

Answer 9

Provide a highly reproducible, well-defined, and replenishable supply of homogeneous (monoclonal) antibody

Question 10

pH and antibody reactions

Answer 10

Most blood group antibodies react at 6.5-7.5 pH

Question 11

Anti-D Binding Temperature

Answer 11

20x more efficient at 37C than 4C

Question 12

Antiglobulin Test

Answer 12

The antihuman Ab bind to the Fc portion of sensitizing Ab and bridge Ab coated red cells, causing agglutination

Question 13

IAT Testing Procedure

Answer 13

1. Cells are sensitized with IgG Anti-D through incubation
2. AHG added
3. Sensitized D+ cells agglutinate, but not by IgG Anti-D

Usually serum is incubated with red cells to sensitize them to antibodies to antigens if they are present, then washed to remove unbound antibody that could inactivate AHG.

Question 14

Detection of Clinically Significant Ab

Answer 14

If Ab are not detected at 37C or IAT are not relevant

Question 15

Applications of the IAT

Answer 15

Unexpected Ab detection/ID, Ab titration, Red cell elute testing for detection/ID, crossmatch

Question 16

Compatibility Test

Answer 16

Encompasses ABO/Rh determination, Ab screen, and crossmatch

Question 17

Incubation Phase Selection

Answer 17

Most US labs do not use an immediate spin/RT phase to avoid detection of cold-reactive Ab, instead use a 37C incubation phase

Question 18

Autoadsorption

Answer 18

Adsorption using the patients’ own red cells if they have not recently been transfused, using heat, enzymes, or a sln that has enzyme and DTT (ZZAP)
Can remove the panreactive autospecificity and leave alloantibodies in the plasma

Question 19

Alloadsorption

Answer 19

Adsorption of autoantibodies if the patient has been recently transfused, using phenotyped O cells that are known to lack common antigens to adsorb the serum
Can remove the panreactive autospecificity and leave alloantibodies in the plasma

Question 20

Positive DAT

Answer 20

Can be more efficiently evaluated if the specificity of the Ab is known
Serum/Plasma reactivity is usually weaker than the DAT; if it’s stronger, there may be an alloantibody present
If Rh phenotyping is being done, a DAT should be done at the same time

Question 21

Negative DAT

Answer 21

Immediate focus is on alloantibody ID

If Rh phenotyping is being done, a DAT should be done at the same time

Question 22

Negative DAT in AIHA

Answer 22

These must be sent to a reference lab for flow cytometry,, Anti-IgG, IgA, and IgM standardized for human cells

Question 23

Paroxysmal Cold Hemoglobinuria

Answer 23

Hallmark test is Donath-Landsteiner Test, uses rare p cells to test for anti-P specificity
Presents in young patients as an acute transient hemolytic anemia w/hemoglobinuria
Caused by a biphasic IgG autoantibody that acts as a hemolysin in warm and sensitizes the cells in cold

Question 24

Cold Agglutinin Disease

Answer 24

Shown by reactions with all reagent cells including autocontrol, DAT is + for Anti-C3
Diagnostic test is the 30C Albumin Test, giving a + in patients with this disease

Question 25

Diamond Blackfan Anemia

Answer 25

Have higher than normal strength i antigen, that persists for longer than in healthy children
Shown in a reference lab by titration, using a 4% suspension of patients cells with a serial dilution of anti-i, giving a quantitative measure of i antigen on cells

Question 26

Drug-Induced Hemolytic Anemia

Answer 26

Has IgG/C3 coated cells –> +DAT, but negative eluate
If in a non-O type patient has a +DAT and negative eluate, it is from an out of group plasma/platelets transfusion and passively acquiring anti-A or B
Can be caused by drug therapy, so a review of medications the patient is on should be done

Question 27

Testing for Drug-related Antibodies

Answer 27

1. Coating red cells with the drug

2. Using suspension of drug added to Pt serum and reagent red cell mix

Question 28

IAT Crossmatch

Answer 28

Crossmatches should be done with 37C and AHG phases, the incubation time at 37C depends on the AHG being used (poly or monospecific)

Question 29

Transfusions in Pts with Clinically Significant Ab

Answer 29

Phenotyping on donor units should be done, so that units that are antigen-negative for the patients’ Ab can be transfused

Question 30

Causes of Incompatible Crossmatches

Answer 30

Ab Screen (-)
- alloAb in recipient to low-incidence Ag on donor cells
- (+) DAT on donor RBCs
- ABO error
- Contaminant in test system
- Polyagglutinable donor cells
Ab Screen (+)
- alloAb
- Contaminant in test system
Ab Screen (+), A/C (+)
- alloAb in previously transfused Pt
- autoAb and alloAb in Pt serum
- Rouleaux
- reaction with enhancement serum

Question 31

Cold-reactive AutoAb, and counteractive procedures

Answer 31

Autoanti-I or high titered cold autoagglutinins cause ABO discrepancies
Prewarming the specimens and maintaining them at 37C prevents the IgM from coating and sensitizing the cells, eventually causing autoagglutination
Adsorption/autoadsorption can also be done prior to reverse typing

Question 32

Cold-reactive Ab

Answer 32

Cause ABO discrepancies, similarly to cold-recative autoAb