Leukocyte function in chronic myeloproliferative disorders

The myeloproliferative disorders (MPD) are clonal diseases that originate f rom a transformed stem cell and involve all myeloid lineage. The affected c ells have both proliferative and functional impairment. Therefore, we evalu ated and compared neutrophil function in 31 patients with polycythemia vera (PV), idiopathic myelofibrosis (MF), chronic myeloid leukemia (CML), and e ssential thrombocytosis (ET). Neutrophil chemotaxis, random migration, bact ericidal activity and superoxide anion release in these patients were simul taneously compared to those of 31 healthy controls. In this study, chemotac tic activity was significantly impaired in patients with PV and CML as comp ared to controls (M+/-SE: 42 +/- 6 vs. 69 +/- 5 cells/field; p<0.005 and 47 +/- 7 vs. 68 +/- 5; p<0.05, respectively). The assessment of the bacterici dal activity of neutrophils showed no impairment in most of the patients. I n the CML group, the serum had a very strong "lytic" effect on bacteria, po ssibly due to the high levels of serum lysozyme (22 +/- 2 ug/ml). The super oxide anion release was found to be normal in most of the patients. Neverth eless, in 25% of PV patients the superoxide production was impaired (less t han 60% of the simultaneous controls). In ET most patients had normal neutr ophil function. Regarding the effect of-treatment, neutrophil chemotactic a ctivity was found to be significantly reduced in the hydrea-treated patient s, as compared to the non-treated patients (p<0.001) or healthy controls (< 0.0001). We conclude that disturbances in neutrophil function are present in patient s with various MPDs, except ET. This probably reflects abnormal maturation of ancessors of the damaged stem cells. Nevertheless, we should keep in min d that therapy itself could affect neutrophil functions. This matter should be studied more extensively. Although infections are not common in MPD dis orders, they occasionally occur. It is possible that impairment in the phag ocytic function contribute to the development of infections in patients wit h myeloproliferative disorders.