Text Notes Flashcards
Macrophage Sources
Kupffer cells in liver, CT histocytes, and fixed cells within the Reticuloendothelial system
Opsonized
Cells targeted because they are coated with antibody or activated complement
Fc Receptor
Non-specific cell surface receptors for antibodies bound to antigen that Macrophages bind to
What percent of peripheral blood lymphocytes are T cells?
70-80%
Immunogen
Is a substance that causes a detectable immune response
Antigen
Is a substance that is capable of reacting with the product of an immune response
Hapten
A larger carrier molecule that attaches to immunogens that can become immunogenic
Difference between “Antibody” and “Immunoglobulin”
Antibody: If the binding specificity is known
Immunoglobulin: A collection of different antibodies with no single binding specificity
Hybridomas
Provide a highly reproducible, well-defined, and replenishable supply of homogeneous (monoclonal) antibody
pH and antibody reactions
Most blood group antibodies react at 6.5-7.5 pH
Anti-D Binding Temperature
20x more efficient at 37C than 4C
Antiglobulin Test
The antihuman Ab bind to the Fc portion of sensitizing Ab and bridge Ab coated red cells, causing agglutination
IAT Testing Procedure
- Cells are sensitized with IgG Anti-D through incubation
- AHG added
- 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.
Detection of Clinically Significant Ab
If Ab are not detected at 37C or IAT are not relevant
Applications of the IAT
Unexpected Ab detection/ID, Ab titration, Red cell elute testing for detection/ID, crossmatch
Compatibility Test
Encompasses ABO/Rh determination, Ab screen, and crossmatch
Incubation Phase Selection
Most US labs do not use an immediate spin/RT phase to avoid detection of cold-reactive Ab, instead use a 37C incubation phase
Autoadsorption
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
Alloadsorption
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
Positive DAT
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
Negative DAT
Immediate focus is on alloantibody ID
If Rh phenotyping is being done, a DAT should be done at the same time
Negative DAT in AIHA
These must be sent to a reference lab for flow cytometry,, Anti-IgG, IgA, and IgM standardized for human cells
Paroxysmal Cold Hemoglobinuria
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
Cold Agglutinin Disease
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
Diamond Blackfan Anemia
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
Drug-Induced Hemolytic Anemia
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
Testing for Drug-related Antibodies
- Coating red cells with the drug
2. Using suspension of drug added to Pt serum and reagent red cell mix
IAT Crossmatch
Crossmatches should be done with 37C and AHG phases, the incubation time at 37C depends on the AHG being used (poly or monospecific)
Transfusions in Pts with Clinically Significant Ab
Phenotyping on donor units should be done, so that units that are antigen-negative for the patients’ Ab can be transfused
Causes of Incompatible Crossmatches
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
Cold-reactive AutoAb, and counteractive procedures
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
Cold-reactive Ab
Cause ABO discrepancies, similarly to cold-recative autoAb
