Acta med. scand. Vol. 199, pp. 321-325, 1976
Lysozyme Activity in Cerebrospinal Fluid Sakari Reitamo and Matti Klockars From the Fourth Department of Medicine, University of Helsinki, Helsinki, Finland
ABSTRACT. The concentration of lysozyme (LZMj in cerebrospinal fluid (CSF) has been studied in 148 patients to evaluate its possible significance in the differential diagnosis of various diseases affecting the central nervous system (CNS). In the control group only 3 of 45 patients had detectable LZM in their CSF, the highest value being 1.3 pg/ml. The diabetic and epileptic groups did not differ from the control group. Of 8 patients with primary intracranial tumours, 4 had raised CSF-LZM levels. Twenty of 23 uraemic patients had elevated CSF-LZM, the highest value being 3.3 & n l . The highest values were found in patients with bacterial meningitis, tuberculous meningitis and leptomeningitis due to Aspergillus. A positive correlation was found between CSF-LZM and protein concentrations. The measurement of LZM may be of value in the diagnosis of inflammatory processes affecting the CNS and in the diagnosis of certain intracranial tumours.
Lysozyme (LZM) is a widely but selective distributed enzyme in man (4, 8 . 1 1 ) . High concentrations of LZM occur in phagocytic cells, polymorphonuclear neutrophils (PMN), monocytes and macrophages, as well as along the gastrointestinal tract and in the kidneys. LZM has not been detected in cells of the central nervous system (CNS) (8j, and normal cerebrospinal fluid (CSF) contains no LZM (4,5 , 6 , 17). However, elevated CSF-LZM levels have been recorded in bacterial meningitis ( 1, 2 , 5, 10, 17), sarcoidosis of the CNS (10) and in certain CNS tumours ( I , 10, 12). This study was undertaken to study possible variations in the concentration of CSF-LZM in a variety of disorders affecting the CNS. MATERIAL AND METHODS The concentration of LZM in CSF was studied in 148 patients: 45 with no evidence of toxic, metabolic or local CNS disease (control group); 23 with non-haemorrhagic 21-762984
thromboembolic cerebrovascular disease; 24 with epilepsia; 16 with manifest insulin-dependent diabetes; 23 with various degrees of renal insufficiency; 8 with intracranial tumours; 7 with bacterial meningitis; 1 with tuberculous meningitis and 1 with leptomeningitis caused by Aspergillus fumigatus. CSF was obtained by conventionally performed lumbar puncture. Specimens were centrifuged at 2000 rpm for 10 min and the supernatant was stored at -20°C until assayed. Some cell-free specimens. of CSF were stored at +4"C for several weeks with no apparent effect on LZM activity. Immediately after puncture the CSF was submitted to cell counts and protein determinations performed by routine methods. LZM was assayed by the lysoplate method described by Osserman and Lawlor, in which purified human LZM is used as standard (14). With the use of 10-pl micropipettes (Eppendorf, West-Germany) for filling the wells, standardized gel thickness and 18-hour incubation at room temperature, LZM activity was detected at enzyme concentrations of 0.9 pg/ml. Values below this figure were considered to be zero. The standard curve in Fig. 1 shows the relationship between the concentration of human LZM (in concentrations of 1-10 fig/ml) and the diameter of the zone of lysis. The immunohistochemical identification of LZM in CNS turnours was demonstrated by an immunoperoxidase method as described previously (8).
RESULTS Fig. 2 gives the concentration of CSF-LZM in a variety of CNS disorders. Control patients. Of the 45 patients who had no evidence of any disease of the CNS, 42 had no detectable (i.e. 150 pmol/l) only three had CSFLZM concentrations below 0.9 pglml. In 20 of these patients the concentration of LZM was between 0.9 and 3 . 3 pg/ml. Bacterial meningitis. All seven patients with bacterial meningitis had raised levels of LZM in their CSF, the lowest being 2.4 and the highest 24.0 pg/ml. In one patient with tuberculous meningitis and one with leptomeningitis due to Aspergillus fumigatus the concentration of LZM in the CSF was high (Table I). We correlated the concentrations of CSF-LZM with the following laboratory findings: serum LZM levels, CSF protein concentrations and serum creatinine levels. In 35 patients there was no correlation between the concentration of LZM in serum and in CSF (Fig. 3). The concentrations of LZM and protein in CSF correlated positively in the 23 uraemic patients (r=O.622,p