CD40LG and tick-borne encephalitis: In our report, the diagnosis of TBE was established by the presence of a febrile illness after a tick bite with headache, mild lymphocytic pleocytosis, and demonstration of serum IgM and IgG antibodies to TBE virus by ELISA, the serologic method of choice with the specificity 99.9% for IgM and 99.5% for IgG and the sensitivity 99.8% and 96.8% for IgM and IgG, respectively (17).