Plasma Lysozyme in Drug-induced and Spontaneous Cyclic Neutropenia

Summary. In order to evaluate how well the plasma lysozyme concentration reflects changes in the neutrophil status in a non-steady state system, six patients, treated with bone-marrow depressing agents, were followed with neutrophil counts and plasma lysozyme determinations. In all patients, plasma lysozyme rather accurately mirrored changes in the neutrophil counts. The minimum change in neutrophil counts detectable by sequential studies of plasma lysozyme concentration was about 1000 neutrophils per μl blood, corresponding to a change in the granulocyte turnover rate of 30 × 107 neutrophils per kg per day. No time lag was found between changes in the neutrophil counts and plasma lysozyme concentrations, which suggests that the life span of the neutrophilic granulocytes in the tissues is less than 24 hr. In the neutrophil nadir phases the plasma lysozyme concentration was consistently higher than expected from the neutrophil counts. This was probably to a large extent due to ‘background’ lysozyme from non-neutrophilic sources, but might in addition suggest a reduced life span in the neutropenic phases. Similar investigations were carried out in two patients with spontaneous cyclic neutropenia. Whereas in these patients little variation of plasma lysozyme with the neutrophil phases could be demonstrated, plasma lysozyme was constantly higher than the concentrations found in the patients with drug-induced neutropenia at similar neutrophil levels. This suggests a reduced neutrophil life span in the patients with cyclic neutropenia, especially in the nadir phases. Kinetic studies of blood neutrophils with DF32P labelling in one of the patients with cyclic neutropenia showed a slightly reduced blood half-disappearance time in the zenith phase and a greatly reduced half-disappearance time in the nadir phase.