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The complement system is a system of proteins that are cascaded in a classic or alternative way. Its stimulation leads to the release of factors that activate chemotaxis, phagocytosis or anaphylaxis. Complement proteins are responsible for inflammation in our body.

The complement system – definition

The complement system is a series of proteins that are actively cascaded, either classically or alternatively. It plays an important role in our body, maintaining its immunity and complementing the role of antibodies. The complement system is classified as non-specific immunity because it cannot recognize foreign antibodies on its own. Complement proteins are produced by monocytes and hepatocytes (liver cells) and are initially inactive. It is only after the appearance of foreign antigens that the complement system is activated. The medical literature describes three ways of activating the complement system:

  1. classical (it takes place with the help of antibodies bound on the surface of microorganisms; successive elements of complement are activated; finally, the death of a foreign cell occurs through its disintegration);
  2. alternative (as in the case of the classical route, the microorganism is killed);
  3. lectin (as above).

Complement proteins dissolve in plasma and body fluids. Elements of the complement system of the classical activation pathway are marked with letters C and the numbers from 1 – 9 Feet. The designation uses the same lowercase letters a, b, c, which allows to better describe the complement activation cascade.

Complement functions

  1. supporting the immune system,
  2. removal of immune complexes,
  3. dissolving and removing bacteria and viruses,
  4. elimination of changed and damaged cells,
  5. chemotaxis (flowing in the place of inflammation of food cells),
  6. release of inflammatory substances.

Complement testing (eg, C3 and C4) is performed to determine whether deficiencies in the complement system cause inflammation in the patient and whether they cause inflammation. The analysis is performed with a blood sample taken from the patient.

Complement system – indications for the examination

Complement testing is performed in the following cases:

  1. suspicion of systemic connective tissue diseases with chronic stimulation of the complement system,
  2. bacterial infections,
  3. angioedema
  4. suspicion of glomerular diseases, vasculitis or rheumatoid arthritis,
  5. kidney problems,
  6. serum sickness,
  7. diagnostics of the causes of recurrent infections,
  8. suspicion of autoimmune diseases, e.g. systemic lupus erythematosus,
  9. inheritance of immune deficiencies.

The course of the study of the complement system

Complement activity is assessed by analyzing the individual proteins that make up the complement system. If a complement component is suspected to be deficient, the total complement activity is determined. The appearance of decreased or increased activity of the complement system in the test results does not allow for the diagnosis of any disease, but suggests that the immune system is involved in the course of a given disease.

Complement material: serum.

Preparation for the test: on an empty stomach (at least 8 hours).

The course of the complement test: one-time blood sampling from a vein in the arm.

Time to wait for the result: 2-3 days.

Standards:

– C3 complement component: 0,75 – 2,0 g / l,

– C4 complement component: 0,1 – 0,3 g / l.

It should be remembered that the reference values ​​depend on many factors, incl. age, sex, method of determination and the studied population. They may have a different scope depending on the laboratory where the test was performed.

Comments: The interpretation of the complement concentration determination must be made in conjunction with the patient’s history and physical examination and the results of other laboratory tests.

Increased and decreased activity of the complement system

The increase in the activity of the complement system occurs most often in the course of the course inflammation acute or chronic. Activity does not normalize until the inflammation has healed. On the other hand, decreased activity of the complement system is observed in the course of the following ailments:

  1. angioedema (hereditary or acquired)
  2. bacterial infections (recurrent),
  3. fungal infection
  4. parasitic infections,
  5. sepsis,
  6. rheumatoid arthritis,
  7. systemic lupus erythematosus,
  8. nephropathy,
  9. glomerulonephritis,
  10. malnutrition.

Complement components can also be lowered due to hereditary deficiencies or increased use of them. Determination of complement component proteins allows for a quick diagnosis of the disease, and thus quick implementation of treatment and its greater effectiveness.

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