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Impaired cellular host defence in peritoneal dialysis by two granulocyte inhibitory proteins
M Haag-Weber1, B Mai, W H Hörl
1Department of Medicine, University of Vienna, Austria.
Abstract:
Bacterial and fungal peritonitis is associated with a high risk of morbidity and mortality in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Impaired cellular host defence in the peritoneal cavity underlies this risk. Two granulocyte inhibitory proteins with a molecular weight of 28,000 dalton (GIP I) and about 9500 dalton (GIP II) with homology to light-chain proteins and beta 2-microglobulin, respectively, were isolated from peritoneal dialysis effluents. In vitro, both granulocyte inhibitory proteins inhibit PMNL glucose uptake, phagocytosis and intracellular killing of bacteria. The IC50 of GIP I or GIP II required for inhibition of half-maximal FMLP-induced or PMA-stimulated PMNL function was found to be in the nanomolar range, suggesting very specific inhibition. These data may explain, at least in part, defective local cellular host defence in CAPD patients.
Insights
Two inhibitory proteins found in peritoneal dialysis fluid impair white blood cell function, potentially explaining increased infection risk in continuous ambulatory peritoneal dialysis (CAPD) patients.
Area of Science:
- Nephrology
- Immunology
- Microbiology
Background:
- Peritonitis, a serious complication of continuous ambulatory peritoneal dialysis (CAPD), leads to significant morbidity and mortality.
- Defective cellular host defense mechanisms within the peritoneal cavity are implicated in the high risk of peritonitis in CAPD patients.
Purpose of the Study:
- To isolate and characterize proteins from peritoneal dialysis effluents that may contribute to impaired cellular immunity.
- To investigate the in vitro effects of these isolated proteins on polymorphonuclear leukocyte (PMNL) function.
Main Methods:
- Isolation of granulocyte inhibitory proteins (GIP I and GIP II) from peritoneal dialysis effluents.
- In vitro assays to assess the impact of GIP I and GIP II on PMNL glucose uptake, phagocytosis, and bacterial killing.
- Determination of inhibitory concentrations (IC50) for GIP I and GIP II on PMNL functions stimulated by FMLP and PMA.
Main Results:
- Two granulocyte inhibitory proteins, GIP I (28 kDa) and GIP II (~9.5 kDa), were isolated and found to have homologies to light-chain proteins and beta 2-microglobulin, respectively.
- Both GIP I and GIP II demonstrated significant inhibition of PMNL glucose uptake, phagocytosis, and intracellular bacterial killing in vitro.
- The IC50 values for GIP I and GIP II were in the nanomolar range, indicating highly specific inhibition of PMNL functions.
Conclusions:
- The identified granulocyte inhibitory proteins (GIP I and GIP II) found in peritoneal dialysis effluents can impair key functions of polymorphonuclear leukocytes.
- These findings provide a potential explanation for the observed defective local cellular host defense in patients undergoing continuous ambulatory peritoneal dialysis (CAPD).
- Further research into these inhibitory proteins could lead to novel therapeutic strategies for managing peritonitis in CAPD patients.