Peritoneal macrophages from patients on continuous ambulatory peritoneal dialysis have an increased capability to release tumour necrosis factor during peritonitis.

We have reported previously that human peritoneal macrophages collected from patients on Continuous Ambulatory Peritoneal Dialysis (CAPD) during an episode of peritonitis secrete increased amounts of interleukin-1 (IL-1), as compared to those collected during an infection free period, provided the cells were stimulated in vitro by LPS. We now report that such macrophages release also higher amounts of Tumor Necrosis Factor (TNF), if collected during peritonitis and stimulated subsequently in vitro by LPS. The increase in release of TNF was ascertained by radio-immunoassays as well as by bioassay of cytostatic effect against the highly sensitive TNF target-cell line L929 murine transformed fibroblasts. The present reported results, in addition to previously reported data on release of IL-1, indicate that induction of release of cytokines from human peritoneal macrophages is a dual stepwise process: first priming in vivo in an inflammatory environment and, secondly stimulation in vitro by LPS.