Complement fixation test (CFT)
Guinea pigs posses higher level of complement than any other laboratory animal, hence Guinea pig serum is the main source of complement in CFT.
The ability of the antigen- antibody complexes to fix complement is made use of in the complement fixation test.
1. If there is no antigen only antibody and complement present, not occurs antigen- antibody complex, the complement is not fix.
Repture of cell.
Complement is free to act on indicator system.
2. If add RBC coated antigen then start binding, having antigen- antibody complex, they can fix the complement.
Complement is fixed in Ag-Ab reaction, adding RBC coated antigen. No reptured of RBC. RBC aggregated in bottom.
Complement is not free to act on indicator system.
Observation
1. Absence of haemolysis
No lysis; positive test
2. Presence of Haemolysis
Break down (lysis) of RBC; Negative test
Uses of CFT
Use in diagnosis of various diseases of different etiology.
Uses of CFT
1. Bacterial diseases
Gonorrhoea, Brucellosis
2. Viral disease
LGV-CFT test
3. Spirochetal disease
Syphilis
4. Rickettsial disease
Typhus fever
5. Parasitic disease
Kala-azar, Amoebiasis
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