CD40LG and tick-borne encephalitis: Inclusion criteria were defined as follows: (1) clinical signs of central nervous system (CNS) disease, (2) cerebrospinal fluid (CSF) pleocytosis or magnetic resonance imaging‐, computed tomography‐, or histopathology‐findings consistent with CNS inflammation, and (3) the presence of either TBE‐virus CSF antibodies, serum IgM, or a four‐fold increase of IgG antibodies in paired serum samples, or a positive TBE‐virus PCR in CNS tissue.