Antibodies IgA, IgM, IgG to Chlamydia trachomatis in blood

Diagnostic antibody titer to Chlamydia trachomatis in the blood: for IgM - 1:200 and higher, for IgG - 1:10 and higher.

During and shortly after acute chlamydial infection, the titer of IgA, IgM and IgG antibodies to Chlamydia trachomatis in the blood increases. The body infected with Chlamydia trachomatis synthesizes antibodies, but these antibodies have a weak protective effect: usually the pathogens persist even in the presence of high antibody titers. Early intensive treatment can inhibit antibody synthesis. Due to the relatively large "antigenic mass" of chlamydia in genital infections, serum IgG antibodies are detected quite often and in high titers. Thus, in children with chlamydial pneumonia, they can be very high: 1:1600-1:3200.

IgM antibodies are detected in the acute period of infection (as early as 5 days after its onset). The peak of IgM antibodies occurs in the 1st-2nd week, then there is a gradual decrease in their titer (as a rule, they disappear in 2-3 months even without treatment). IgM antibodies are directed against lipopolysaccharide and the main protein of the outer membrane of chlamydia. The presence of IgM antibodies indicates the activity of chlamydia. IgM antibodies do not penetrate the placenta, are synthesized in the fetus and belong to the newborn's own antibodies. Their presence indicates infection (including intrauterine) and indicates an active process. The IgM-AT titer may increase during reactivation, reinfection or superinfection. Their half-life is 5 days.

IgA antibodies are synthesized to the main protein of the outer membrane and a protein with a molecular weight of 60,000-62,000 chlamydia. They are detected in the blood serum 10-14 days after the onset of the disease, their titer usually decreases by the 2nd-4th month as a result of successful treatment. In case of reinfection, the IgA antibody titer increases again. If the IgA antibody titer does not decrease after a course of treatment, this indicates a chronic or persistent form of infection. Detection of a high IgA antibody titer often indicates a pronounced autoimmune process in the patient, most often found in patients with Reiter's syndrome. In such patients, the presence of IgA antibodies indicates a severe course of the disease.

IgG antibodies appear 15-20 days after the onset of the disease and can persist for many years. Reinfection is accompanied by an increase in the existing IgG antibody titer. Determination of the titer of antibodies to chlamydia in the blood must be carried out dynamically; evaluation of the research results based on a single study is unreliable. IgG antibodies penetrate the placenta and form anti-infective immunity in newborns. High titers of IgG-AT protect the fetus from infection, as well as women from salpingitis after artificial termination of pregnancy; in addition, they provide short-term protection (up to 6 months) from repeated infection with chlamydia. The half-life of IgG-AT is 23 days.

To establish a diagnosis, it is necessary to simultaneously determine IgA and IgG class antibodies; if the IgA result is unclear, IgM antibodies must be additionally examined.

Newborns and their mothers are examined on the 1st-3rd day after birth, in case of a negative result in the presence of a clinical picture of the disease - again on the 5th-7th and 10th-14th day. The presence of IgM antibodies during a repeated examination indicates a congenital infection (maternal IgM antibodies do not penetrate the placenta). The absence of anti-chlamydial antibodies in newborns does not mean the absence of chlamydial infection.

Determination of the titer of antibodies to Chlamydia trachomatis in the blood is an auxiliary test for the diagnosis of chlamydia, since due to low immunogenicity, antibodies are not detected in 50% of patients with chlamydia.

Determination of IgA, IgM and IgG antibodies to Chlamydia trachomatis in the blood is used to diagnose chlamydial infection in the following diseases:

• urethritis, prostatitis, cervicitis, adnexitis;
• pneumonia, inflammatory diseases of the lungs;
• Reiter's disease, Behcet's syndrome, infectious arthropathies.

Diseases caused by Chlamydia trachomatis

Trachoma. Chronic keratoconjunctivitis begins with acute inflammatory changes in the conjunctiva and cornea and leads to scarring and blindness.

Chlamydial antigens in epithelial cells are determined in conjunctival scrapings using the fluorescence method. They are most often detected in the early stages of the disease in the upper part of the conjunctiva.

Urogenital chlamydia and conjunctivitis. The frequency of detection of chlamydia in men with non-gonococcal urethritis is 30-50%. Infection of women having their first pregnancy reaches 5-20%, having an abortion - 3-18%. Among patients with signs of cervicitis, chlamydial infection is detected in 20-40% of cases; salpingitis - in 20-70% of cases; urinary tract infection - in 5-10% of cases.

Fitz-Hugh-Curtis syndrome is also considered an early complication of chlamydial infection; it is an acute peritonitis and perihepatitis accompanied by ascites.

Respiratory tract lesions caused by Chlamydia. Adults with chlamydial conjunctivitis often develop symptoms of upper respiratory tract lesions (pharyngitis, rhinitis, otitis, etc.), which apparently develop as a result of the spread of chlamydial infection through the nasolacrimal canal. Pneumonia does not usually develop in adults. In newborns infected by their mothers, respiratory system lesions up to pneumonia are possible 2-12 weeks after birth.

Reiter's syndrome (disease) Reiter's syndrome is characterized by the classic triad: urethritis, conjunctivitis and arthritis. In this syndrome, chlamydia can be detected in the synovial fluid. An increase in the titer of IgA, IgM and IgG antibodies is noted during the development of an active joint infection.

Endocarditis. Clinically, it occurs rapidly, with significant damage to the aortic valves.

Latent infection may manifest spontaneously as a low-symptom complication. More than half of patients have signs of chronic prostatitis and/or sacroiliitis.

Currently, methods that allow detection of Chlamydia trachomatis antigens in the test material (ELISA, fluorescent antibody method, PCR) are used to diagnose chlamydial infection. Determination of the titer of antibodies in the blood serum to Chlamydia trachomatis is an auxiliary method for diagnosing chlamydia.

[ 1 ], [ 2 ]