CD79A and cyst: When it occurs, the persistence of T. gondii IgA (or IgM) antibodies in chronic infections may be explained by factors such as patient heterogeneity, infecting parasite stage (oocyst versus cyst), immune status at the time of blood collection, time of blood sampling relative to the time of onset of infection, assay technique (25), or parasitemia during cases of serologic reactivation (22).