Endotoxin-stimulated peritoneal macrophages obtained from continuous ambulatory peritoneal dialysis patients show an increased capacity to release interleukin-1 beta in vitro during infectious peritonitis.

Interleukin-1 (IL-1) release by peritoneal macrophages obtained from patients on continuous ambulatory peritoneal dialysis (CAPD) was studied in nine patients during an infection-free period and eight patients during an infectious peritonitis, using an ELISA for IL-1 beta. Without exogenous stimulation with LPS, peritoneal macrophages from infected and uninfected patients released the same amounts of IL-1 beta, 183 +/- 40 pg ml-1 24 h-1) per 10(6) cells (means +/- SEM) and 251 +/- 96 pg ml-1, respectively. However, in response to a dose of 5 micrograms ml-1 of LPS, peritoneal macrophages released significantly more (P less than 0.005) IL-1 beta during peritonitis (6579 +/- 2793 pg ml-1 24 h-1 per 10(6) cells) compared with the infection-free period (1040 +/- 182 pg ml-1). These findings show that after microbial invasion of the peritoneal cavity, peritoneal macrophages are primed in vivo to release an increased amount of IL-1 beta in vitro after subsequent exogenous stimulation with LPS, indicating that peritoneal macrophage activation for IL-1 beta secretion occurs in steps.