To assess its role in TBE, we have studied CCR5 in activated Th lymphocytes (CD3+CD4+CD45RO+) in csf, a cell population that is relatively accessible, reflects the intrathecal inflammatory/immune response, is important for TBEV clearance from cns, and which appears to be preferentially recruited into csf of TBE patients. This evidence concerns the gene CD4 and tick-borne encephalitis.