Syphilis is an infection caused by the bacterium Treponema pallidum. Both men and women are affected, usually of reproductive age. Ways of transmission - sexual and vertical. A risk factor is the frequent change of sexual partners. Infection occurs after the first contact of biological fluids of the body with the tissues of another person.
In response to the penetration of bacteria, the body immediately begins to react. Immunity reactions are carried out with the help of humoral and cellular immunity.
When infected with syphilis, the mechanisms of the innate nonspecific and adaptive, antigen-mediated immune response are activated in the body. Many mediators of cell metabolism (regulatory and anti-inflammatory interleukins, growth factors and other oligopeptides) take part in the immune response. Their increased content can be determined in the circulating blood or in the foci of infection locally. The quantitative content of these peptides reflect the severity of the protective reaction. But these indicators are not characteristic markers of syphilis and are not used for the differential diagnosis of infectious diseases.
Humoral immunity is carried out due to specific antibodies that are produced in plasma cells. According to modern opinion, the humoral response is represented by class M immunoglobulins. This is a pantamer, in which there are 5 identical subunits, each of which is formed by 2 light and 2 heavy chains of amino acids. Antibodies of class M are considered the most ancient antibodies of protective forces. In blood serum, their amount reaches 10% of the total amount of immunoglobulins. IgM maximally bind foreign antibodies and prepare them for removal from the body. Due to its molecular structure, IgM can bind up to 10 antigen molecules at the same time. Features of the FC-structure of molecular regions and the large size of immunoglobulin do not allow it to penetrate through vascular membranes and tissue barriers.
Class M immunoglobulins can be detected in the blood as early as 10-14 days after the penetration of Treponema pallidum through the mucous membranes. The maximum concentration of bacteria in the body is reached already at 6-9 weeks.IgM are quickly eliminated from the bloodstream (after 3-12 months). If the patient does not receive treatment for syphilis, then gradually the synthesis of IgM is replaced by the synthesis of IgG. These proteins are smaller, because in their structure they correspond to only one IgM subunit. Each IgG molecule can bind only 2 antigen molecules. Therefore, these proteins are more active, penetrate through vascular membranes, tissue barriers and the placenta. In the blood, the concentration of IgG is 75% of all immunoglobulins. Their function is to bind antigens in hard-to-reach places for other Ig.
As for specific IgG in syphilis, they appear in the blood 3-4 weeks after infection. Their content gradually increases and reaches its maximum after 1.5 years, after which it may decrease or fluctuate in waves. It depends on the activity of the infectious process. After adequate treatment, IgG is detected in the blood as a marker of past infection, but in smaller quantities and can be determined in the blood for life.
In addition to these immunoglobulins, IgA, which are synthesized on the surface of the mucous membranes of the respiratory tract, genitourinary tract, respiratory and digestive systems, takes part in the body's response to infections. Proteins are monomers and dimers with two subunits. In the blood, the concentration of Ig A reaches 15-20% of the total pool of immunoglobulins. These proteins are not able to penetrate the baby's blood through the placenta. This feature is used to diagnose congenital syphilis.
- enzymatic immunoassay (ELISA);
- passive haemagglutination test (RPHA);
- indirect immunofluorescence reaction (RIF);
- immunoblotting (IB);
- immunochromatographic (ICHI) and immunochemiluminescent (ICLI) research methods.
Studies have been conducted aimed at studying the clinical informativeness of IgM detection by ELISA. When examining 73 patients, it was found that in the blood of patients with primary syphilis, the maximum concentration of IgM was observed in combination with the minimum amount of IgG.
In secondary syphilis, when Treponema pallidum has massively disseminated the body, the opposite picture occurs - IgM decreases and IgG titer increases.
In the study of Chepurchenko N.V. and Kiseleva G.A. the authors made conclusions about the sensitivity of ELISA to IgM. With primary syphilis – 78-93%, secondary - 51-85%, with hidden forms - 24.3-64%.
After the treatment, IgM is not detected in the blood after 6-12 months in 71-92% of cases.
If IgM still persists in the body, this indicates a re-infection or ineffective treatment.
Also highly sensitive is the method for determining IgM in serum – REEF. Studies have shown 100% sensitivity of the method for primary and secondary syphilis and 96% for early latent syphilis.
The study of the serum of patients with a clinic of congenital syphilis gave a high clinical sensitivity to the detection of IgM antibodies in a new method - immunoblotting – 92%.
Thus, for the early diagnosis of infectious diseases, including primary, secondary, congenital syphilis or reinfection, the most appropriate is the detection of IgM. To determine them, the doctor, depending on the situation, the stage of the process and the proposed form of the disease, chooses the most appropriate method.
If at least one symptom of syphilis is detected, the doctor should conduct research for the early detection of syphilis, determining the form of the disease and for timely treatment. After all, what is "fresh" infection, the easier and more effective its treatment. And for successful treatment, it is important to know the form of the disease and the amount of immunoglobulins and antibodies.
Remember! By detecting syphilis in time using the determination of immunoglobulins, the doctor saves tens and even hundreds of people from the potential danger of being infected with syphilis.
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