Leukocyte C5a receptor modulation during hemodialysis

Area of Science:

• Immunology
• Nephrology
• Biomaterials

Background:

• Hemodialysis (HD) involves blood exposure to artificial membranes, potentially activating the complement system.
• Complement activation can lead to inflammatory responses and impact immune cell function.

Purpose of the Study:

• To investigate the effect of hemodialysis membranes on the binding of chemotactic factors and immune complexes to polymorphonuclear leukocytes (PMN) and monocytes.
• To compare these effects in normal individuals versus patients with chronic renal failure undergoing hemodialysis.

Main Methods:

• Flow cytometry was used to analyze the binding of fluoresceinated C5a, f-Met-Leu-Phe-Lys (fMLPL), casein, and aggregated IgG to PMN and monocytes.
• Blood samples were collected from normal subjects and chronic hemodialysis patients at various time points during dialysis and incubated with dialysis membrane fibers in vitro.

Main Results:

• In normal blood, hemodialysis membrane passage progressively decreased C5a binding to PMN and monocytes over 45 minutes.
• No significant changes in binding of fMLPL, casein, or aggregated IgG were observed in normal blood.
• In chronic hemodialysis patients, no significant differences in C5a, fMLPL, casein, or aggregated IgG binding were found at different time intervals.
• PMN from normal subjects showed a loss of C5a receptors after in vitro incubation with dialysis membranes, while PMN from HD patients did not.

Conclusions:

• Hemodialysis membranes induce a loss of C5a receptor function on immune cells in normal individuals.
• Chronic hemodialysis patients may develop an adaptation, showing resistance to this membrane-induced C5a receptor downregulation.