High avidity of specific IgG antibodies and the lack of early markers of active infection (IgM and/or IgA class antibodies) suggest chronic toxoplasmosis, and therefore allow discontinuation of testing subsequent serum samples, whereas low avidity of high IgG titers and the simultaneous presence of specific IgM and IgA antibodies make it possible to suspect active toxoplasmosis. This evidence concerns the gene CD40LG and toxoplasmosis.