In 88 patients with the diagnosis of Lyme neuroborreliosis the intrathecal synthesis of antiborrelial IgG antibodies was assessed by two independent methods: a) assessment of antigen non-specific and specific oligoclonal immunoglobulins G by the qualitative method of isoelectric focusing with sub- sequent immunoblotting, b) by a quantitative method using calculation of the specific antibody index from the titres assessed in serum and cerebrospinal fluid by the ELISA method. The diagno sis was assessed on the basis of manifestations of the nervous affection and evidence of specific antiborrelial antibodies in the cerebrospinal fluid by the ELISA test. In 74 patients antibodies class IgG were found, in 14 patients antibodies class IgM. Non-specific oligoclonal immunoglobulins G were detected in 33 patients of 74, incl. 31 patients where it proved possible to detect also antigenic specificity. Of 72 patients with concurrently detected antiborrelial IgG antibodies in blood and cerebrospinal fluid in 39 intrat- hecal synthesis of specific antibodies calculated by means of the antibody index were found. The results indicate a greater sensitivity of the assessment of the antibody index (54.1 %) for e vidence of intrathecal secretion as compared with assessment of specific oligoclonal immunoglobulins G (38.8 %). In 16 patients serologically infection with the virus of Central European tick-borne encephalitis was proved, however 12 of them had an increased permeability of the blood-brain barrier. Only in four patients a positive antiborrelial antibody index was found which suggested dual viral and borrelial infection.

        Key words: intrathecal synthesis of IgG antibodies, neuroborreliosis, non-specific oligoclonal IgG