Neutrophils are critical effector cells in humoral and innate immunity and play a vital role in phagocytosis and bacterial killing. If they and/or their specific functions are lacking, then immunoparalysis may occur, and severe diseases like systemic inflammatory response syndrome (SIRS) or sepsis can take a fatal course. In this paper, we discuss the possibility of using preconditioned cells in an extracorporeal biohybrid immune support system. A human promyelocytic cell line was stimulated for different times with all‐trans retinoic acid. The resulting cells displayed major signs and functions of mature neutrophilic granulocytes including oxygen radical production, phagocytosis of living and dead Escherichia coli, Staphylococcus aureus, Candida albicans, intracellular killing, and interleukin production. The cells can be expanded to yield a sufficient cell mass, and subsequent prestimulation results in an expression of specific neutrophil functions. Extracorporeal bioreactor experiments seem to be feasible to test the benefit in immunoparalysis‐associated diseases like SIRS or sepsis.

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Granulocyte dysfunction is a central component of immunodeficiency in septic patients. Granulocyte transfusions appear to be pathophysiologically useful; however, they cause unwanted side-effects in the lungs and other organs. This study evaluates the safety of an extracorporeal immune support system with granulocytic cells in a rat model of Gram-negative sepsis. Three groups of male CD rats received either saline (control group, I), a dose of Escherichia coli O7:K1 lethal to 90% of the animals (LD90) (septic group, II), or an LD90 dose of E. coli that was incubated with the human promyelocytic leukemia cell line (HL-60) (differentiated into the granulocytic direction) for 20 min prior to infusion (second septic group, III). The animals were observed for seven days. Pre-treatment with HL-60 cells resulted in no adverse effects in the group III animals. Significantly lower bacterial counts and endotoxin levels in the plasma were detected after 24 h as compared to group II (P < 0.05). Group III animals had better weight gain and more stable hemodynamics than group II animals (P < 0.01). Seven day survival was 0/8 in group II, 6/8 in group III, and 8/9 in group I (log-rank test: II-III: P < 0.001). The data suggest that extracorporeal use of granulocytes allows the therapeutic use of these cells while avoiding unwanted effects resulting from direct contact to internal organs.