CD40LG and infection: The other four patients had avidity and AC/HS test results which suggested that a recent infection may have been present; these negative T. gondii IgM antibody test results may have occurred because testing was performed shortly after T. gondii IgM antibody titers decreased or these patients may be similar to those reported recently by European investigators, namely, acutely infected patients negative for T. gondii IgM antibodies (30).