The complement system is a group of proteins that, when activated, will cause the lysis of target cells and promote phagocytosis through opsonization. Individual complement components can be quantified, but this does not provide any information about the activity of this pathway. Total complement activity/CH 50 (also known as CH 100) is a screening assay for activation of the classical complement pathway. It is sensitive to the reduction, deletion, and/or inactivation of any component in the pathway. The total complement activity test can fully understand the activation status of the complement system, so as to better determine the occurrence, severity and response to treatment. Therefore, the complement activity test has very important clinical significance in the diagnosis and subsequent treatment of diseases.
The most common methods to test the functional activity of the complement system include hemolysis assays or automated methods, such as liposome lysis and enzyme-linked immunosorbent assay (ELISA). Creative Biolabs has an extensive complement function assay platform that can determine the specific activity of all three pathways without interference from other pathways. We provide a comprehensive complement activity test menu and have the expertise to develop customs complement assays for diagnosis, research and clinical trials.
Assay Principle
Total complement activity/CH50 tested the classical pathway of serum complement components to lyse sheep red blood cells (SRBC) pre-coated with rabbit anti-sheep red blood cell antibodies (hemolysin). When the antibody-coated SRBC is incubated with the test serum, the classical pathway of complement is activated and hemolysis occurs. If there is no complement component, the total complement activity/CH50 level will be zero; if one or more components in the classical pathway are reduced, CH50 will decrease. A fixed volume of the best sensitized SRBC was added to each serum dilution. After the incubation, the mixture was centrifuged, and the degree of hemolysis was quantified by measuring the absorbance of hemoglobin released into the supernatant at 540 nm. The amount of complement activity is determined by examining the ability of various dilutions of the test serum to lyse the antibody-coated SRBC.
Clinical Significance
CH50 is a measurement method for the functional integrity of the complement system and is used to monitor the overall activity of dietary complement diseases. Sometimes it is more sensitive than C4 or C3. However, its main value is as a shield for complete defects of components other than C3 and C4. If the latter is normal and CH50 is missing or very low, it indicates that other complement components are defective, so a more complete assessment of the complement system is needed.
Increased plasma concentrations of C3 and C4: common in inflammatory processes. C3 and C4 are acute-phase proteins and can be seen with the increase in CRP and ESR (erythrocyte sedimentation rate). With the increase of C3 and C4 as acute-phase proteins, even if the protein is rapidly consumed, its levels sometimes still appear normal.
C3 and C4 are both decreased: when the classical pathway is activated, immune complex-mediated diseases such as systemic lupus erythematosus/SLE-complement depletion (septicemia) usually occur.
C3 decreased, C4 normal: common when the alternative pathway is activated (gram-negative sepsis)
C3 is normal, C4 is decreased: Type II ice globulinemia associated with hepatitis C infection-lack of C1 inhibitors; active SLE; genetic deficiency (C4 has no allele).
Sample requirements
1 ml of serum, separated from the blood clot within one hour after venipuncture. For the best evaluation, samples should be received within 24 hours after separation. Artifacts rarely occur during transportation at room temperature. If the transportation time is expected to be longer, it is recommended to transport at -20°C.
Reference range
The reference range depends on the method. Users should refer to the "PRU Manual" and the relevant laboratory.
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