CD40LG and disease arising from reactivation of latent virus: Thus IgG- and IgM-anti-TG antibody positivity associated with IgA positivity or low IgG avidity is indicative of an acute infection, while IgG-anti-TG positivity, IgM- and IgA-anti-TG negativity or high IgG avidity are indicative of latent infection [23].