Serum and urinary lysozyme in leukaemia and polycythaemia vera

Evidence for a bimodal relation between serum lysozyme and prognosis in 232 patients with acute myeloid leukaemia

Lysozyme values are sometimes used as an aid for diagnostic subtyping of acute myeloid leukaemia (AML), since monocytic forms often show high levels. We wanted to study if pretreatment serum lysozyme has any relation to prognosis in AML. For this purpose, 232 adult AML patients who had received remission induction therapy at two hospitals were reviewed retrospectively. Their median age was 65.5 yr. Sixty-three patients were FAB classified as "monocytic" AML (M4, M5) and 169 as "non-monocytic" AML (M0, M1, M2, M3, M6). A linear relation was rejected, and a bimodal relation was found between lysozyme and prognosis where values below 20 or above 80 mg L-1 were indicative of better outcome than values in the range 20-80 mg L-1. Analysed in three categories with cut-off levels at 20 and 80 mg L-1, lysozyme showed an independent effect on complete remission (CR) frequency (P = 0.0003), overall survival (P < 0.0001), and CR duration (P = 0.0005) in multivariate analysis. The hazard ratios (HR) for lysozyme <20, 20-80, and >80 mg L-1 regarding overall survival were 1.0, 3.3, and 0.7. Influence of lysozyme on survival was bimodal both in "non-monocytic" AML (HR 1.0, 3.0, and 0.1) and M4-M5 (HR 1.0, 10.1, and 1.2). Our finding of a bimodal relation between serum lysozyme and prognosis in AML should be regarded as a new hypothesis and controlled in other studies.

Polycythemia vera megakaryocytes store and release lysozyme to a higher extent than megakaryocytes in secondary polycythemia (polyglobuly)

Lysozyme, a myelomonocytic marker not only exerts bacteriolytic, but also immunomodulatoric properties and was found to bind to the glycosaminoglycan serglycin, an important constituent of the extracellular matrix (ECM). Pathological serum lysozyme levels were described in chronic myeloproliferative disorders (CMPDs) and other hematological conditions. In this context it is remarkable that in polycythemia rubra vera (PV), characterized by a proliferation particularly of the megakaryo- and erythropoiesis, serum lysozyme levels behave independently of the numbers of myelomonocytic cells in peripheral blood. To elucidate whether megakaryopoiesis might be the source of the increased serum lysozyme, we performed an experimental study on isolated and enriched megakaryocytes derived from bone marrow of patients with PV. Findings were compared to a group of patients with reactive (smoker's) polyglobuly (PG). In confirmation of previous results, quantification of serum lysozyme levels showed a slight elevation in the cohort of PV patients which was not correlated with the leukocyte count. Applying an immunohistochemical assay we were able to demonstrate intracytoplasmic lysozyme storage in megakaryocytes. Moreover, performing the reverse hemolytic plaque assay (RHPA), a technique which enables detection of secreted proteins at the single cell level, we found that 54% of the PV, but only 3% of the PG megakaryocytes spontaneously secreted lysozyme. After rhIL-3 treatment the secretion of lysozyme remained unchanged in PV but increased to 14% in PG. These findings suggest that the extent of megakaryocytic lysozyme secretion might discriminate PV from reactive conditions. Although a direct involvement of lysozyme in the regulation of aberrant megakaryopoiesis in PV is not likely, the results of the present study point to the possibility that lysozyme could be involved in the interactions of PV megakaryocytes with ECM. Moreover, the response to rhIL-3 significantly discriminates PV megakaryocytes from megakaryocytes of the PG group.

Distinct lysozyme content in different subtypes of acute myeloid leukaemic cells: an ultrastructural immunogold study

Using an ultrastructural immunogold method, we performed a quantitative study on cellular lysozyme (LZ) content in young normal bone marrow cells and in 14 cases of acute myeloid leukaemia (AML) of the M2, M3, M4 and M5 types. In five cases of M2 we found significantly lower LZ content than in normal promyelocytes and than in nine cases of M3, M4 and M5. In M3, M4 and M5 cells a very high LZ content was observed whereas the serum LZ activity was high in M4 and M5 and normal in M3. The intragranular LZ content was especially high in M5 and in most granules of M4 cells. The immunogold reaction (IGR) for LZ was also performed in cells previously reacted for myeloperoxidase (MPO). In M2 the granules showed definite positive MPO reactivity and low LZ density (granulocytic pattern), whereas in M5 we found high granular LZ content and weak or almost negative MPO activity (monocytic pattern). In M4 we found 'granulocytic' and 'monocytic' type of granules in the same cell. The IGR for LZ performed in post-embedded M5 cells which were previously subjected to phagocytosis of latex particles, showed granules that had moved toward the phagosome, releasing LZ without degranulation. The above findings and those showing normal serum LZ in M3 despite their high cellular LZ content, definitely indicate that only leukaemic M4 and M5 cells secrete LZ into their environment, explaining the high serum LZ observed in those leukaemias.

A method for automatic recording of serum lysozyme activity with the fragiligraph

A quick and simple method for the estimation of lysozyme activity using the Fragiligraph, was described. Diminution of turbidity in a suspension of Micrococcus lysodeikticus produced by the addition of standard lysozyme (hen egg white) or serum sample, was continuously recorded for 5 min by the Fragiligraph. The normal mean serum lysozyme activity value obtained by this method is 6,80 mug/ml +/- 1.85.

Granulocyte release of vitamin B12-binders in vivo and in vitro in leukaemia and non-neoplastic leucocytosis

The unsaturated vitamin B12-binding capacities of the 'large molecular size vitamin B12-binding protein' (LBP) and the 'small molecular size vitamin B12-binding protein' (SBP) were determined by a Sephadex G 150 gel filtration method in 9 patients with chronic myelocytic leukaemia (CML), 5 patients with blast cell leukaemia and 12 patients with non-neoplastic leucocytosis. EDTA plasma and serum separated after 20 min and after 120 min were examined. In the 20 min EDTA plasma samples, the mean LBP value was 8,009 pg/ml in CML, 2,468 in blast leukaemia, 175 in non-neoplastic leucocytosis, and 57 in normal controls. The in vitro release of LBP into serum was much smaller in the leukaemias than in non-neoplastic leucocytosis. No correlation was found between the LBP values and the white blood cell counts or lysozyme values, but lysozyme was correlated to white cell count in CML. It is suggested that the plasma LBP levels reflect the fraction of LBP decay taking place at sites, e.g. the spleen, from which the released LBP can enter the circulation.

Cell production and cell function in human cyclic neutropenia

In vitro studies have been done on haematopoietic cells from a patient with cyclic neutropenia characterized by severe depression of blood neutrophil levels every 21 days. Serial blood counts reveal periodic fluctuations in neutrophils, monocytes and reticulocytes. Agar culture of marrow cells shows normal concentration of colony forming cells. The percentage of colony forming cells in S phase is highly increased during profound neutropenia and normal during the recovery phase relating the granulocyte production to the peripheral neutrophil level. Studies of ingestion rate, bactericidal activity, lactate production and glucose oxidation during phagocytosis in isolated granulocytes show normal results. Also the ingestion rate in isolated monocytes is normal. Serial karyotype analyses of marrow cells during the neutrophil cycle display a normal pattern. Serum myeloperoxidase levels vary inversely with the peripheral neutrophil count indicating increased granulopoietic activity during profound neutropenia, which might be associated with non effective granulopoiesis during profound neutropenia, leading to a lack of granulocyte reserves in the marrow.