Serous meningitis is a relatively frequent disease which can be caused by viruses - in the Czech Republic the most frequent causal agent is the virus of tick-borne meningoencephalitis - and some bacteria (Borrelia burgdorferi, Leptospira grippotyphosa etc.). The authors made a pilot study involving pheno- typic analysis of lymphocytes in cerebrospinal fluid and peripheral blood using flow cytometry. They assessed lymphocytic sub-populations and activated T lymphocytes in cerebrospinal fluid of 24 patients with tick-borne meningoencephalitis, in 15 patients with serous meningitis of unknown etiology (mostly caused by viruses) and in 12 patients with spirochetal neuroinfection. In 13 patients with tick-borne meningoencephalitis and in 10 patients with the spirochetal neuroinfection sub-populations in the peripheral blood stream were also assessed. On comparison by the Student t-test no differences were found in the lymphocytic sub-populations in viral neuroinfections of the cerebrospinal fluid. On comparison of sub-populations in cerebrospinal fluid and blood in tick-borne meningoencephalitis in CSF a very significant increase was observed (p < 0.01), as well as an increase of the relative number of total T lymphocytes and CDF4 + T lymphocytes and a significant reduction of the relative number of CD8 + T lymphocytes and B lymphocytes; in spirochetal neuroinfections the comparison was similar. On comparison of lymphocytic subpopulations in CSF in tick-borne meningoencephalitis and in spirochetal neuroinfections the authors recorded in spirochetal neuroinfections a significantly higher relative number of B lymphocytes (p = 0.0042). Immunophenotypic analysis of lymphocytes in serous meningitis helps in investigations of immune mechanisms in the CNS.

        Key words: flow cytometry, cerebrospinal fluid, peripheral blood, lymphocyte sub-sets, tick-borne