CD40LG and Epstein-Barr virus infection: The presence of EBV nuclear antigen (EBNA) IgG antibodies, or the absence of both IgG and IgM antibodies to VCA, rules out an acute primary EBV infection and warrants consideration of other causes for a mononucleosis-like illness, such as cytomegalovirus (CMV), primary HIV infection, and toxoplasmosis.