Immunology Flashcards
What are Human Leukocyte Antigens (HLA)?
HLA are antigens that play a major role in transplantation and transfusion.
What is the importance of HLA typing/testing?
It helps predict transplant rejection, prevent GVHD, and match platelets.
Define Zeta Potential.
Zeta Potential refers to the difference in electrostatic charges on the surface of red cells and surrounding cations.
What are the major forces influencing antigen-antibody binding?
- Electrostatic forces
- Hydrogen bonding
- Hydrophobic bonding
- Van der Waals forces
What are the two stages of the agglutination reaction?
- Sensitization
- Lattice formation and agglutination
What are clinically significant antibodies?
Antibodies that can cause decreased red cell survival, usually IgG or IgM that reacts at 37°C.
What are clinically insignificant antibodies?
Antibodies that do not cause decreased red cell survival post-transfusion, typically IgM.
What is platelet refractoriness?
A condition where patients receiving multiple platelet transfusions develop antibodies against HLA antigens, leading to poor response.
What is the significance of the zone of equivalence?
It is the optimal ratio of antigen and antibody where agglutination occurs.
Fill in the blank: The first stage of in vitro Ag-AB binding is usually not _______.
visible
What is the role of temperature in antigen-antibody reactions?
Temperature affects the rate of reaction; IgG reacts best at 37°C and IgM at 4°C.
How long is the lag phase in primary immune responses?
5 to 10 days.
What are the reagents used to reduce Zeta Potential?
- LISS
- PEG
What is the difference between affinity and avidity?
- Affinity: strength of binding between a single antibody and epitope
- Avidity: overall strength of reactions between several epitopes and antibodies
What is the significance of the ‘Prozone’ phenomenon?
Excess antibodies saturate all antigen sites, preventing agglutination.
What is Zeta Potential (ZP)?
A cloud of ions attracted to the negative charge on red cells
How do IgM and IgG antibodies react differently to Zeta Potential?
IgM do not require potentiator; IgG require enhancement media for optimal reactivity
What is the effect of decreasing Zeta Potential on agglutination?
Decreases ZP increases agglutination
What are enhancement solutions or potentiators?
Products that enhance antibody uptake and promote direct agglutination
What is the purpose of LISS?
To reduce ZP and enhance antibody uptake during sensitization
What is PEG used for?
To concentrate antibody and enhance antibody uptake in IAT methods
What should not be done when using PEG?
Do not centrifuge or read reactions before washing the mixture
What is the effect of proteolytic enzymes on antibodies?
Enhance agglutination of IgG antibodies by reducing negative charge on red cell surface
Name some proteolytic enzymes used in antibody testing.
- Papain * Ficin * Trypsin * Bromelin
