An antibody titer is the maximum dilution of blood serum that contains specific antibodies. When studying the immune status, one dilution of the serum is made, respectively, attached to the test system (1:50, 1: 100), after which, if necessary, titration is recommended by successive two-fold dilutions.
It has been established that if there are antibody titers in the analysis to an inverse value of 1: 600-1: 800, there is a directly proportional relationship between the optical density index and the antibody titer value of this serum. Above this inverse value, a similar dependence is violated, and upon subsequent double titration (1: 1600, 1: 3200, 1: 6400, etc.), an error occurs, which is greater, the greater the dilution.
Consider in more detail that this is an antibody titer.
Varieties of antibodies
Throughout life, the human body βgets to knowβ various pathogens, chemicals, and cell breakdown products. In response to this, he produces his own immunoglobulins, which are also called blood antibodies - these are specific protein compounds that are formed from lymphocytes and act as stimulants of the immune defense.
Many are interested in what antibody titers mean. In immunological studies, several types of antibodies that act strictly on specific antigens are distinguished. They are determined using the titration method and they include:
- IgM is the initial immunoglobulin that begins to be produced when an infection enters the body. Its role is to stimulate immunity to the primary fight against the pathological process. The presence of IgG in the blood is observed 3-5 days after the onset of the disease. These antibodies form a stable immunity to certain infections, are responsible for the effectiveness of vaccination.
- IgA - protect the digestive tract, respiratory tract and urinary system from harmful microbes. They bind pathogenic objects, preventing them from gaining a foothold on the mucous membranes.
- IgE - are activated to protect the body from fungi, parasites and allergens, and are localized mainly in the bronchi, stomach and intestines. These antibodies are involved in the formation of secondary immunity. In blood plasma in their free form, they are practically nonexistent.
- IgD is a fraction that is still not well understood. It is believed that these agents are responsible for local immunity, begin to be produced during exacerbation of myeloma or chronic infections. In serum, less than 1% of the fraction of all existing immunoglobulins is constituted.
All antibodies can be freely present in the blood plasma or attach to the surfaces of infected cells. Having recognized the antigen, specific proteins begin to bind to it using the tail. It serves as a special signal for immune cells responsible for the processes of neutralization of foreign objects.
Types Based on Interaction
Considering how proteins interact with antigens, they are also divided into several types:
- Anti-infectious - bind to the body of pathogens, destroying them.
- Antitoxic - do not affect the vital activity of foreign bodies, but neutralize the toxins produced by them.
- Autoantibodies are substances that trigger the mechanism of the occurrence of autoimmune disorders by attacking healthy cells in the body.
- Alloreactive are immunoglobulins that act against the antigens of cells and tissues of other organisms of the same biological species. A study to determine the antibodies of this fraction is carried out by titration during transplantation of various organs.
- Isoantibodies are protein compounds that are produced against cell agents of other biological species.
- Anti-idiotypic - compounds that are designed to neutralize an excess of their own antibodies.
How are antibody titers analyzed? This is a very common study.
Blood test
A modern method of laboratory diagnosis of various diseases is considered to be an ELISA (immunofluorescence analysis). This antibody test allows you to determine the titer (functionality) of immunoglobulins, their variety and establish at what stage of development is a particular pathological process.
Algorithm
The method for determining the titer of antibodies consists of several stages: first, the laboratory assistant receives blood serum from a person. The resulting sample is placed on a specialized plastic plate with the presence of holes in which there are purified antigens of the desired pathogens or protein (in cases where it is necessary to determine the antigen). A special staining substance is added to the wells, which, when a positive enzyme reaction occurs, changes the color of the immune complexes. According to the staining density, a conclusion is drawn on the results of a blood test for an antibody titer.
The timing
To conduct this test, researchers need one to three days. The analysis itself is of two types: qualitative and quantitative. In the first case, it is indicated that the desired antigen will be found in the blood serum or, conversely, absent. A quantitative type test is carried out in accordance with a more complex chain reaction and allows us to draw a conclusion about the concentration of antibodies, establish their variety, evaluate the speed with which a pathological infectious process develops.
Indications for appointment
It is impossible to cover the full list of indications for ELISA, however, the most common goals of this analysis are to diagnose acute and chronic forms of such infectious pathologies:
- IgG to HIV;
- IgM and IgG to hepatitis of viral origin A, B, C, E;
- IgM and IgG to cytomegalovirus;
- IgM and IgG to herpes;
- Epstein-Barr IgM and IgG;
- IgG for parasitic diseases;
- IgM and IgG to toxoplasmosis;
- IgM and IgG - titers of antibodies to measles, rubella, salmonellosis, tick-borne encephalitis, dysentery and other diseases;
- IgM and IgG for infections that are transmitted through the genital tract;
- Helicobacter pylori IgG;
- for the purpose of a general assessment of immunity indicators and markers of autoimmune diseases;
- determination of oncological markers (tumor necrosis factor, prostate-specific antigen, cancer-embryonic antigen and others);
- determination of the level of blood hormones (progesterone, prolactin, testosterone, thyroid stimulating hormone and others).
Decryption
Normally, antibody titers should not be in the analysis. The result of a qualitative type of study is an unambiguous conclusion: the desired substance is either not found or found in a blood sample. If we are talking about a quantitative type of analysis, then the concentration can be expressed by a numerical value or by the number of β+β signs.
The analyzed indicators are considered:
- IgM - the presence of this class of immunoglobulins indicates an acute course of the infection process in the body. Their absence may indicate the absence of the pathogen or the transition of the pathological process to the chronic stage.
- IgA with a negative IgM test result in most cases indicates a latent or chronic infection.
- The joint presence of IgM and IgA - two positive results indicate the height of the acute phase of the existing pathology.
- IgG - chronization of a disease or recovery and the formation of immunity to a specific infectious agent.
Many patients are interested in the question - what does the negative result mean? No antibody titers? The result, which is marked with a β-", is considered negative and means that no immunity to a specific infectious pathogen has been detected in the patient's body.
Another important quantitative indicator is the avidity index of antibodies, which is expressed as a percentage. It indicates how much time has passed from the beginning of the development of the infectious process. The higher the index, the longer the period.
Advantages of the technique
The indisputable advantages of this research methodology are its specificity and high sensitivity. Sensitivity means the ability to recognize the desired element, even if its content in the sample is low. Specificity implies an error-free diagnosis: if the results are positive, then it is precisely those antibodies or antigens that were suspected to be detected.
A high degree of manufacturability of enzyme-linked immunosorbent assay by titration minimizes the impact of the human factor, which significantly reduces the likelihood of error. The bulk of reagents and test systems for ELISA used in modern clinics are produced under industrial conditions, which guarantees a reliable result.
The main disadvantage
The main disadvantage of this diagnostic technique is that for its implementation it is necessary to know what exactly needs to be found. The analysis implies that the doctor presumes in advance what pathological agent caused this or that disease.
Another drawback of this study is that ELISA for antibody titers is a rather expensive blood test method, which is often not affordable for many patients. And this means that the doctor should approach the appointment of such a diagnosis wisely.