Antigen and Antibody Reactions (Agglutination Tests | P) Flashcards
What is the principle of direct agglutination?
The pt’s serum is tested against large, cellular Ags to screen for the presence of Abs
In connection to direct agglutination, Ag is present on what?
Ag is naturally present on the surface of the cells
What is the result of direct agglutination?
The Ag-Ab rxn forms an agglutination w/c is directly visible
Slide agglutination test is used for what?
It is used for serotyping (ex. ABO)
In the slide agglutination test, what is the Ag and where is it present?
The Ag is the isolated RBC w/c is present in the suspension
In the slide agglutination test, where is the Ab present?
This is present in the sp antisera used against RBC Ags
What is the process (or steps) of slide agglutination test?
1) Add a drop of antiserum to various drops of blood present in the slide
2) Mix
3) Rock the slide for approx 1 min
4) Examine for the presence of agglutination
What is the principle of hemagglutination?
It detects Ab to erythrocyte Ags
What are the principles of rxns for hemagglutination?
1) Sufficient concentration of Ab present -> Ab cross-link = agglutination
2) Non-reactive / insufficient Ab present = no agglutination
*What is the general principle of rxn of hemagglutination?
Binding diff Ags on the RBC surface = detect Abs to Ag other than those present in the cells
*What is utilized in Coombs (antiglobulin) tests?
Incomplete Abs
What is the principle of direct Coombs test?
It detects Abs on RBCs
What is the principle of rxn of direct Coombs test?
*Pt’s RBCs + Coombs rgnt (antiglobulin) Ag-Ab rxn
What is the principle of indirect Coombs test?
It detects anti-erythrocyte Abs in serum
*What is the process (or steps) of indirect Coombs test?
1) Pt’s serum + target RBCs Ag-Ab rxn
2) The present Ag-Ab rxn + Coombs rgnt (antiglobulin) more Ag-Ab rxns
What is the importance of complement?
It takes part in many of the immunological rxns
What happens to complement during the combination of Ags and Ab?
It gets absorbed
What is the meaning of CF (or CFT)?
Complement fixation test
What is the property of Ag-Ab complex that is used in CFT and what is its purpose?
The property of Ag-Ab complex to fix the complement for the identification of sp Abs
What are the components of the hemolytic system?
1) Sheep RBCs
2) The corresponding Ab (amboceptor) for sheep RBCs
What is the fxn of amboceptor?
It is used as an indicator w/c shows the utilization or availability of the complement
What are the results for CFT?
1) If the complement is fixed = no lysis of sheep RBCs; denoting a (+) test
2) If the complement is available = hemolysis of sheep RBCs is present; denoting a (-) test
*What is the property of complement?
Hemolysis
What is the principle of CF?
Ab and Ag are allowed to combine in the presence of complement
What happens if the complement is fixed by sp Ag-Ab rxn?
It will be unable to continue w/ indicator system
What are the precautions that must be observed in CF?
1) The serum must be heat-activated
2) Stored serum becomes anti-complementary
3) Extensive QC / standardization is required to be done
4) IgM Abs should only be used
What are the components of CFT?
1) Test system
a. Ag
b. Ab
c. Complement
2) Indicator system (Hemolytic system)
a. Erythrocytes
b. Amboceptor (Hemolysin)
What is the characteristic of Ag (being present in CFT)?
It may be soluble or particulate
What is the source of Ab (present in CFT)?
It can be found in the human serum, however, the human serum may or may not contain Ab towards sp Ag
What is complement (present in CFT)?
It is pooled serum that is obtained from 4 - 5 guinea pigs
What should be the considerations (in relation to complement) that should be considered for CFT?
1) The complement should be fresh or specially preserved
2) The complement activity should be initially standardized before using in the test
Why should the complement be fresh or specially preserved for CFT?
Because the complement activity is heat labile
What is the storage temp for complement since it is heat labile?
It should be stored at -30 DC in small fractions
What are the erythrocytes used for CFT?
Sheep RBCs
*What is the amboceptor used in CFT?
Rabbit Ab
Where do the amboceptor react?
It reacts w/ sheep RBCs
*How can rxn bet rabbit Ab and sheep RBCs occur?
In terms of preparation, the sheep RBCs are inoculated into the rabbit Ab under std immunization protocol
What is the process (or steps; or principle) for a (+) CFT test?
1) Ag + Ab + complement (from serum) -> complement gets fixed (at 37 DC in 1 hr)
2) Fixed complement complex + hemolytic system -> there will be no hemolysis (at 37 DC in 1 hr) -> w/c denotes a (+) CFT test
