Dissociation between cytostatic and cytolytic activity of human monocytes towards K-562 cells

The cytolytic and cytostatic activities of human monocytes towards K-562 cells were compared by determining release of 3H-thymidine and DNA synthesis rate (i.e. thymidine incorporation), respectively. The inter-individual variations were substantial, with significant correlation between cytostasis and cytolysis in the entire experimental material (26 blood donors), but not in monocytes kept in vitro for 90 min or 1 day before the start of assay. A significant level of correlation between cytolysis and cytostasis was observed in monocytes kept in vitro for 4 days before assay (coefficient of correlation = 0.7). The low degree of correlation at each test-time-point prohibits the prediction of cytostatic capability of human monocytes in individual experiments from determination of monocyte-mediated target cell lysis.