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Host defence in continuous ambulatory peritoneal dialysis: the effect of the dialysate on phagocyte function
Abstract:
Peritoneal dialysis fluid was examined after dwell periods of from 30 min to 18 h. Macrophages formed more than 70% of all cells recovered, irrespective of dwell time. The viability of these cells was 95% or greater even in 30 min effluent. Peritoneal macrophages and polymorphonuclear leucocytes were incubated in unused peritoneal dialysis fluid. By 30 min the viability of polymorphonuclear leucocytes had fallen to 50% but that of peritoneal macrophages was still 84%. However, phagocytosis of unopsonized zymosan by both cell types was depressed after only 10 min exposure. Peritoneal dialysis effluents obtained after dwell times of 30-180 min were examined for their effect on phagocytosis in vitro. These fluids suppressed peritoneal macrophages function as compared to RPMI 1640. Effluent after an overnight dwell did not affect phagocytosis. The suppressant effect decreased with increasing dwell time. Polymorphonuclear leucocytes were affected to a greater degree than peritoneal macrophages. Tests showed that this decreased phagocytosis was not due to cell death nor was it due to the osmolality or lactate content of the dialysate. Adjusting pH only improved cell function slightly. Phagocyte function appears to be depressed for clinically significant periods of the CAPD cycle.
Insights
Peritoneal dialysis fluid impairs immune cell function, particularly phagocytosis, within minutes of exposure. This effect lessens with longer dwell times, but remains significant during the continuous ambulatory peritoneal dialysis cycle.
Area of Science:
- Immunology
- Nephrology
- Cell Biology
Background:
- Peritoneal dialysis (PD) is a vital treatment for end-stage renal disease.
- The peritoneal membrane serves as the dialyzing surface, involving complex cellular interactions.
- Understanding the impact of PD fluid on peritoneal immune cells is crucial for patient outcomes.
Purpose of the Study:
- To investigate the effects of peritoneal dialysis fluid on the viability and phagocytic function of peritoneal macrophages and polymorphonuclear leukocytes.
- To determine how dwell time influences these cellular responses to PD fluid.
Main Methods:
- Analysis of cell populations and viability in PD effluent after varying dwell times (30 min to 18 h).
- In vitro incubation of peritoneal macrophages and polymorphonuclear leukocytes with unused PD fluid.
- Assessment of phagocytosis of unopsonized zymosan by immune cells exposed to PD fluid and effluents of different dwell times.
- Evaluation of factors like osmolality, lactate, and pH on cell function.
Main Results:
- Macrophages constituted over 70% of recovered cells, maintaining high viability (>95%) even with short dwell times.
- Polymorphonuclear leukocytes showed significantly reduced viability (50%) after 30 min in PD fluid, compared to macrophages (84%).
- Phagocytic capacity of both cell types was depressed within 10 minutes of exposure to PD fluid; this suppression decreased with longer dwell times and was not linked to cell death, osmolality, or lactate.
Conclusions:
- Peritoneal dialysis fluid acutely suppresses phagocyte function, with polymorphonuclear leukocytes being more susceptible than macrophages.
- The immunosuppressive effect of PD fluid diminishes with increasing dwell time.
- Phagocyte dysfunction during the continuous ambulatory peritoneal dialysis (CAPD) cycle may have clinical implications for peritoneal defense mechanisms.