When an antigen binds to its corresponding antibody, the resulting antigen-antibody complex is able to absorb the complement from the solution, which is called complement binding. The antigen involved in the complement binding reaction is a transparent solution, so the phenomenon of complement binding cannot be seen by the naked eye, so it is necessary to use the hemolysis system as an indicator to determine whether there is free complement in the medium.
Operation method
complement binding reaction
Materials and Instruments
Typhoid fever extracts Move I. Preparatory tests For more product details, please visit Aladdin Scientific website.
Guinea pig serum Rabbit serum Sheep red blood cells
Small test tubes Test tube racks Water baths
The preparatory tests include titration of hemolysin potency, titration of complement potency, titration of antigen potency and handling of the serum being tested.
1. Titration of hemolysin potency: add the substances according to the following table. 
Where the highest dilution of hemolysin can show complete hemolysis as a unit. According to the results of the above table, the 10th tube (i.e., 1:4000 times dilution) 0.5 ml of hemolysin is a unit, in the hemolytic reaction is commonly used in 0.5 ml containing 2 hemolysin units of solution, so the test should be taken 1:2000 times dilution of the solution.
2. Complement unit titration: add the reagents according to the table below. 
The smallest amount of complement that can cause complete hemolysis is called the exact unit, the third tube (i.e., 0.3 ml) in the above table, but because there may be a partial loss of the potency of the complement, the common slightly higher tube is the utility unit, and two utility units must be used for the actual test.The results of the above table are:Standard unit of complement: 0.3 mlPractical unit of complement: 0.35 mLTwo practical units of complement: 0.70 millilitersSince the test is two practical units of complement 0.5 ml, it can be converted according to the following proportionality:20: 0.7 = x: 0.5x = 14.3This means that the complement must be diluted 14.3 times, and 0.5 ml contains two practical units.
3. Titration of antigensWhen an unknown antibody is measured with a known antigen, the antigen potency must be titrated to determine the optimum concentration of antigen required for the test (and vice versa for the determination of an unknown antigen with a known antibody). 
If the serum is completely or partially unhemolyzed against the control tubes it is an anticomplement phenomenon. Serum is often strongly antiexosomal when it is heavily contaminated with bacteria, mixed with lymphatic fluid, or significantly hemolyzed. Anti-complement can also occur if test tubes and pipettes are not clean. If anticomplement occurs, blood should be drawn and retested.