The aim of our study was the detection of specific, intrathecal, antiviral IgG antibodies against the viruses of measles (M), rubella (R) and varicella zoster (VZV) in cerebrospinal fluid (CSF) from patients with definite multiple sclerosis. This specific immune reaction in CSF is called MRZ reaction and occurs in chronic, inflam - matory, autoimmune diseases of the nervous system. Intrathecal synthesis of specific antiviral antibodies is calculated and expressed as the specific antibody index (AI). Intrathecal synthesis is present with values of AI>1.4. Methods: We investigated a cohort of 17 patients (n=17): 14 patients were diagnosed as multiple sclerosis and 3 patients served as negative controls. The samples of CSF and serum were stored at –20 °C. To investigate specific IgG antibodies against viruses (measles, rubella, varicella zoster) we used the diagnostic kit of Human company, Germany (M,R,Z Virus Human ELISA IgG Antibody Test). This kit is based on immunoenzymatic detection type-sandwich. For the calculation of specific, intrathecal antibody synthesis, we converted the absolute values of absorbances to arbitrary units (AU) according to Reiber’s method. The concentrations of albumin and total IgG were measured by nephelometry. Oligoclonal IgG bands were detected by isoelectric focusing. Results: Intrathecal synthesis of specific antiviral antibodies, i.e. MRZ reaction expressed as elevated values of antibody indices, was positive in 92% patients with multiple sclerosis. The positive antibody index against measles was detected in 78% of patients, against rubella in 42% and varicella zoster in 50% of MS patients. The patients who served as negative controls had values of AI in the normal range (0.7–1.3). Conclusion: MRZ reaction significantly improves possibilities of CSF diagnostics, especially in cases of chronic, inflammatory and autoimmune diseases. With its high specificity it supplements more sensitive but less specific methods as oligoclonal IgG bands or magnetic resonance patterns.

        Key words: specific antibody index – AI, MRZ reaction, multiple sclerosis.