Many diseases are much more often characterized by a violation of the ratio of plasma protein fractions (dysproteinemia) than by a change in their total amount. Monitoring the dynamics of these changes helps to determine the disease of the disease, how long it lasts, and how successful the treatment is.
Proteins of different fractions differ from each other in size, shape, charge. This causes a different speed of their movement in the medium used under the action of an electric field (capillary electrophoresis method) and allows them to be separated into fractions. In this case, bands of different sizes are formed, the location of which is specific for each protein fraction. Determination of the proportion of each type of proteins is carried out according to the intensity of the bands formed.
The fraction of albumin is the main one and makes up about 2/3 of the total amount of blood proteins. Albumin is produced by the liver and performs the following tasks:
- maintain the osmotic pressure, which ensures a balance between the water content in the tissues of the body and inside the vessels, as well as the ability of water to remain in the circulating blood and maintain the elasticity of tissues and organs;
- bind cholesterol, bilirubin, calcium, a significant amount of medicinal substances;
- transport various biologically active substances (vitamins, hormones, minerals, fatty substances, etc.);
- serve as a reserve and source of amino acids, decaying when there is a deficiency in the intake of protein into the body to amino acids, which are then involved in the production of proteins of vital organs.
When examining the blood of a healthy person, the albumin forms the most intense band.
The α1-globulin fraction includes acute phase proteins. Their main representative is α1-antitrypsin, which weakens the action of proteolytic enzymes that break down amino acids and take an active part in the digestion of food protein by the stomach and intestines – trypsin, chymotrypsin, plasmin and others. The second component of the fraction, α1-acid glycoprotein, performs many tasks, incl. promotes the formation of collagen fibers in the connective tissue in the area of inflammation (fibrillogenesis). Proteins that act as transporters are also referred to as globulins. Among them are thyroxine-binding globulin, trancortin, α1-lipoprotein. These proteins bind and transport cortisol, thyroxine and lipids, respectively.
The α2-globulin fraction consists of acute phase proteins – α2-macroglobulin, captoglobin, ceruloplasmin. The main component of the fraction – α2-macroglobulin, performs the function of protection in the event of inflammatory processes and infection. The task of the glycoprotein haptoglobin is to combine with hemoglobin, which is released from erythrocytes when they are destroyed inside the vessels. Its utilization is carried out by the cells of the reticuloendothelial system. Ceruloplasmin is able to bind copper ions. In addition, it oxidizes ascorbic acid, adrenaline, dioxyphenylalanine, and neutralizes free radicals.
The β-globulin fraction includes:
- transfennin (tolerates iron);
- hemopexin – by binding heme, it thereby preserves iron in the body, preventing the kidneys from excreting it;
- immunoglobulins (partially) and complement constituents, which are responsible for the state of the immune system.
Immunoglobulins not included in the β-globulin fraction are included in the γ-globulins. They are represented by the following types: IgE, IgM, IgA, IgG, IgD. In fact, these are antibodies designed for the body’s humoral immune defense against foreign bodies and infection. So:
- IgE is normally present in very small quantities; an increase in the level of antibodies of this class is observed with the development of an allergic reaction;
- IgM is the response of the immune system to an acute infection and are produced first when it enters the body;
- IgA predominates in the secretions of the body (saliva, digestive juice, secretions of the mammary glands and nasal mucosa) and are the first line of defense on the mucous membranes of the body, preventing the penetration of viruses;
- IgG is the main class of antibodies in the blood and intercellular fluid, binding viruses, fungi, bacteria and protecting the body from infection throughout the body;
- IgD is the smallest class of antibodies. Their functions presumably include the activation of the production of antimicrobial substances by B-cells, mast cells and basophils, as well as the addition or replacement of IgM immunoglobulins if their performance is impaired.
The normal ratio of protein fractions is disturbed during the development of various acute or chronic inflammations, benign and malignant tumors in the body. Deficiency of a certain type of protein is reflected by the absence of the corresponding band. Most often, this effect is observed with immunodeficiency or insufficient amount of alpha-1-antitrypsin. An increase in the intensity of any of the bands indicates an excess of the corresponding protein. Most often, the cause of the phenomenon is various types of gammopathies. The accumulation of a large amount of a homogeneous protein (paraproteinemia) – usually immunoglobulins or fragments of their molecules, secreted by B-lymphocytes, is reflected during electrophoresis in the form of an additional discrete line. If we depict the result of the study in the form of a graph, where the content of each fraction is characterized by a certain height, then a pathologically high level of a certain type of protein is defined as a peak.
The study of protein fractions can be prescribed by different specialists (for example, rheumatologists, therapists, gastroenterologists, immunologists, cardiologists, endocrinologists, hematologists, nephrologists, etc.) since a change in their ratio is provoked by many factors. However, this analysis plays the most significant role in the diagnosis of monoclonal gammopathies, in particular:
- multiple myeloma;
- Waldenstrom’s macroglobulinemia;
- monoclonal gammopathy of unknown origin and some other pathologies.
A characteristic feature of all these conditions is the proliferation of a clone of B-lymphocytes or plasma cells, followed by the uncontrolled production of immunoglobulins of the same idiotype (class) formed by the tumor. As noted above, when conducting a blood test of a patient with monoclonal gammopathy, a narrow intense band appears in the area of gamma globulins. Its presence may indicate excessive synthesis:
- with multiple myeloma – immunoglobulin IgG;
- with Waldenstrom’s macroglobulinemia – IgM immunoglobulin;
- with monoclonal gammopathy of unknown origin – IgA immunoglobulin.
For all the diagnostic significance of the study of protein fractions, this method does not allow separating the classes of pathological proteins – it serves to roughly estimate the relative amount of abnormal immunoglobulins. Differential (refined) diagnostics is carried out using another method – immunoelectrophoresis, which makes it possible to more accurately determine the amount of M-protein and differentiate between monoclonal gammopathies. Despite the impossibility of using this test to accurately determine the type of pathology, it can be used to assess changes in the level of M-protein, if the diagnosis of multiple myeloma has already been established and confirmed.
Medical practice has shown that in 10% of patients diagnosed with multiple myeloma, the ratio of protein fractions remains normal. Therefore, research results that do not go beyond the reference values cannot completely exclude the presence of pathology. On the other hand, an insignificant presence of M-proteins is possible in chronic hepatitis or in the elderly. It is benign. Simulation of small paraproteinemia (false positive result) can be created by C-reactive protein and other acute phase proteins in large quantities, fibrinogen present in serum, as well as some medications in limiting concentration (immunosuppressants and antineoplastic drugs based on monoclonal antibodies).
Gammopathy can be not only monoclonal, that is, characterized by pathological production of one type of immunoglobulins, but also polyclonal – in which there is a simultaneous hyperproduction of different classes of immunoglobulins. During electrophoresis, this pathology is manifested by a uniform increase in the intensity of the band of gamma globulins and the absence of peaks. The reasons for the development of polyclonal gammopathy can be many infectious or autoimmune inflammatory processes, as well as liver diseases (in particular, hepatitis).
In addition to the above, a change in the ratio of protein fractions in blood serum may also reflect the presence of various immunodeficiency syndromes.
Therefore, one of the applications of this test is the diagnosis of immunodeficiency conditions, a representative of which is Bruton’s agammaglobulinemia. Pathology is characterized by a decrease in the level of all classes of immunoglobulins. When conducting a blood test in patients with Bruton’s disease, the absence or very low intensity of the band of gamma globulins is observed. At a low intensity of the alpha-1 globulin band, we can confidently talk about the lack of alpha-1-antitrypsin.
The spectrum of diseases and pathological conditions causing a change in the ratio of protein fractions in blood serum is very wide and includes diseases of many internal organs. Therefore, the study of quantitative and qualitative changes in the total blood protein fractions makes it possible to diagnose and control the treatment of infections, inflammations, oncological and other diseases. At the same time, a number of diseases are characterized by the presence of typical deviations in the proteinogram, which makes it possible to accurately diagnose them. However, in many cases, based on the results of the study, it is impossible to make an unambiguous diagnosis, therefore, the interpretation of the study data must necessarily be carried out taking into account additional laboratory, clinical and instrumental indicators.
Indications for the study
- As part of a comprehensive survey;
- Diseases associated with diffuse damage to the connective tissue (Collagenosis);
- Acute and chronic infections;
- If you suspect malabsorption syndrome;
- Autoimmune pathologies;
- Pathology of the liver and kidneys;
- To differentiate puffiness;
- Thermal burns;
- To identify malignant processes;
- Wonderstrom disease, rheumatoid arthritis, systemic lupus erythematosus.
Preparation for analysis
- The last meal should be completed 8 hours before the study, but the hunger period should be no more than 14 hours;
- It is recommended to drink clean water, excluding any drinks;
- Do not drink alcohol a day before blood sampling, smoking is allowed no later than an hour before the analysis;
- The result of the analysis is influenced by hormonal drugs, including oral contraceptives, as well as cytotoxic drugs. If it is impossible to exclude their intake, it is necessary to provide a list of drugs to the doctor.
What do the test results mean?
Any deviations from the norm, especially the appearance of peaks and a pronounced excess or deficiency of any fraction, are a serious reason for consulting a doctor and further examination since they may indicate the presence of serious pathological processes in the body. However, one should remember that protein electrophoresis is a non-specific test and is not sufficient to establish a diagnosis.
With monoclonal gammopathies, an uncontrolled production of one type of immunoglobulins (IgG, IgM or IgA) occurs, which is reflected in the results of electrophoresis by the appearance of a narrow intense peak of gamma globulins – the so-called M-peak. This indicator is an important diagnostic criterion, however, it does not allow distinguishing myeloma from gammopathy of another genesis, since the electrophoresis method itself is not able to determine the type of immunoglobulin, the production of which is increased. For this, another study is used – Typing of paraprotein in blood serum (using immunofixation with a panel of IgG, IgA, IgM, kappa, lambda antisera).
With polyclonal gammopathy, there is no pronounced M-peak; instead, an increase in the entire band of gamma globulins is observed. This may indicate chronic inflammatory processes in the body, autoimmune diseases and liver disease.
In immunodeficiency states, the concentration of immunoglobulins decreases sharply, which is reflected as a result of the analysis by the absence or low intensity of the band of gamma globulins. An example of such a disease is Bruton’s agammaglobulinemia.