How can serological testing be used to detect latent infections?

Serological testing can detect latent infections by identifying antibodies or immune responses to specific pathogens, even if the individual is not currently showing symptoms. Here’s how:

1. IgG antibodies: IgG antibodies indicate past exposure or infection. Their presence suggests a latent infection, as the immune system has already responded to the pathogen.
2. IgM antibodies: IgM antibodies typically indicate recent or acute infection. However, some pathogens, like Toxoplasma gondii, can persist in the body, and IgM antibodies may remain detectable during latency.
3. Avidity testing: Avidity testing measures the binding strength of antibodies to a specific antigen. Low avidity suggests recent infection, while high avidity indicates past exposure or latency.
4. Western blot or immunoblotting: These tests detect specific antibodies to particular pathogens, helping identify latent infections.
5. PCR (Polymerase Chain Reaction) and other molecular tests: While not serological tests, PCR can detect pathogen DNA in blood or tissues, indicating latent infection.