CD40LG and viral encephalitis: In terms of the guidelines, special immunoglobulin M (IgM) antibody tests in CSF samples of patients with encephalitis are helpful in diagnosis, but we did not conduct routine special IgM antibody tests of CSF samples, leading to the possible omission of pathogen diagnosis because of the rapid degeneration of pathogen nucleic acid before sample collection or the availability of very few viral sequences to be detected (Tunkel et al., 2008).