Anti-Yersinia
Yersinia is often only detectable in stool samples for a short time, and cannot be detected at all in joints affected by reactive arthritis. For these reasons, the serological detection of Yersinia-specific antibodies is important. The ORGENTEC tests for Alegria detect IgA and IgG antibodies against characteristic Yop proteins (Yersinia outer membrane proteins). The Yop proteins are plasmid-encoded virulence factors and are highly specific for all of the Yersinia species that are pathogenic to humans. After initial exposure to the pathogen, IgM antibodies are formed first, soon followed by the IgG and IgA antibodies. IgM antibodies usually disappear after a few weeks. High IgA and IgG antibody titres are indicative of infection in the recent past. IgG antibodies may persist at low levels for years.