Flow cytometric evaluation of phagocytosis by peripheral blood polymorphonuclear leucocytes in human periodontal diseases

Abstract

The complement-dependent phagocytic functions of polymorphonuclear leucocytes (PMNL) in peripheral blood from 15 patients with localized juvenile periodontitis (LJP), 13 with generalized juvenile periodontitis (GJP) and 52 with adult periodontitis (AP), and from 30 normal subjects as controls were measured by flow cytometry. Heparinized blood was collected and incubated with fluorescent microspheres, and erythrocytes were removed. By means of single-cell analysis the percentage of phagocytosing cells (% phagocytosis) and the mean number of microspheres phagocytosed by one PMNL (degree of phagocytosis; d-phagocytosis) were measured. Some but not all patients with LJP (53%) and GJP (46%) showed consistently low % phagocytosis and d-phagocytosis. On the other hand, only 6% of AP patients and no healthy subjects showed a reduction of PMNL phagocytosis. Phagocytosis was unchanged after initial periodontal treatment in all subjects, suggesting the depression of PMNL phagocytosis may not be a transient phenomenon associated with periodontal status. Furthermore, PMNLs from the LJP patients that showed depressed phagocytic function exhibited depressed phagocytic responses with either autologous or normal plasma, while control PMNLs with either normal or the patients' plasma showed normal responses. These results suggested that the depressed phagocytic responses in LJP patients could be due to cell-associated defect(s) on the PMNL.