PRINCIPLES OF SEROLOGIC REACTIONS Flashcards
Aggregation of PARTICULATE/INSOLUBLE antigens
Agglutination
Aggregation of SOLUBLE antigens
Precipitation
Cells carrying antigenic molecules on their surfaces
Particulate Antigens
Clumping of particles; Presence of lattice formation
Agglutination
2 Stages of Agglutination
- Sensitization
2. Lattice formation
Initial binding of Ab-Ag complex; No visible reaction
Sensitization
TRUE or FALSE: Sensitization is dependent on the nature of Ab&Ag surfaces and on the binding of the antibodies to the epitopes.
TRUE
TRUE or FALSE: Sensitization is irreversible.
FALSE
Factors affecting Sensitization:
- Particle charge
- Antibody type
- Antigen-to-antibody ratio
- Antigenic determinants
- Physical conditions (pH, temp., duration of incubation)
This refers to the net negative charge on the surface of inert particles (RBCs, latex, bacteria)
Zeta potential
Clustering of ions present in the cellular environment around antigens
Neutralizes the opposite charges of Ab & Ag
Ionic cloud
Decreases the ionic strength of the reaction and the zeta potential of inert particles
Low ionic strength saline
Charges of ions are remedied by ______; promotes Ab-Ag binding
Centrifugation
Promotes cross-linking of Ab & Ag
Enzymatic treatment
Best agglutinin because of their large size and multi-valency
IgM
Too small to overcome the electrostatic forces present in the ionic cloud
IgG
Used to enhance the reaction for IgG-mediated agglutination
Anti-human globulin (AHG) methods
TRUE or FALSE: The fewer the antigenic sites, the more effective in stimulating sensitization.
False
TRUE or FALSE: The number and placing of antigenic sites affect sensitization.
True
pH of medium used during sensitization
6.5-7.5
At _____ pH, high electrolyte conc. will act on the net negative charge of particles, thus leading to binding.
Neutral
Cold-reacting antibodies
IgM
Warm-reacting antibodies (37 deg. Celsius)
IgG
15-60 mins.
Range of incubation time
Visible phase of agglutination
Lattice formation
Establishment of cross-links (interchange of hydrogen bonds) between sensitized cells and antibodies, resulting in agglutination
Lattice formation
