The anti Chlamydia antibodies they are antibodies directed towards antigens deriving from the Chlamydia bacterium.
There Chlamydia, improperly defined Chlamydia, is a gram negative bacterium, responsible for sexually transmitted infections, and responsible for venereal diseases such as pelvic inflammatory disease, trachoma and venereal lymphogranuloma. Chlamydia, and in particular Chlamydia Trachomatis, can also cause urinary tract infections (non-gonococcal urethritis), conjunctivitis and, in newborns, also pneumonia.
Chlamydia also appears to be involved in the inflammatory-autoimmune process that leads to the development of Reiter's syndrome, especially in people with a positive HLA B27 gene.
Two other types of Chlamydia, Chlamydia psittaci and CHlamydia pneumonie, once entered under the genus of Chlamydia, are actually now classified as another genus, that of Chlamydophila.
Routine serological diagnostics is based on three methods: complement fixation reaction, immunofluorescence, ELISA.
Complement fixation reaction
It is sensitive, but not very specific. It can be used for the diagnosis of lung infections and venereal lymphogranuloma.
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It detects antibodies directed against the genus specific antigen for which cross reactions exist between the two species (Chlamydia psittaci, C. trachomatis). It allows to search for total anti Chlamydia Ig (immunoglobulins) and specific IgM (immunoglobulins M), which usually persist for 1 to 2 months. The presence of IgM (excluding the presence of rheumatoid factor) and a significant increase in the total antibody rate (i.e. in the presence of seroconversion) allow the diagnosis of recent infection. The search for specific secretory IgA (immunoglobulin A) in secretions is not decisive for the diagnosis.
With the ELISA technique, species-specific and genus-specific antigens are highlighted.
It is the most sensitive method for diagnosing infection with Chlamydia and constitutes the reference method; it allows to evaluate the single classes of immunoglobulins and therefore to differentiate previous infections from those in progress. According to the Grayston criteria in acute infections there is a seroconversion, or values of IgM less than 1:16 and IgG (immunoglobulin G) less than 1: 512. The relief of a title IgG between less than 1:16 and less than 1: 512 points to a previous infection.
The test also allows a differentiation between first infection (in which the IgM response appears after about 3 weeks and the IgG response after 6) and infection (the IgM response may be missing and the IgG response occurs rapidly after 1-2 weeks, also associated with increase in IgA antibodies). After an acute Chlamydial infection, the IgM disappear after about two to three months; IgG decreases slowly, while IgG tends to disappear more rapidly, with a half-life of about 5-6 days.
In reinfections, the IgA response is often the predominant feature. The persistence of IgA antibodies is currently considered a more reliable marker of chronic Chlamydia infection than IgG antibodies.Tags: Laboratory medicine Blood