Background Immune cell dysfunction plays a central role in sepsis-associated immune paralysis. The transfusion of healthy donor immune cells, i.e., granulocyte concentrates (GC) potentially induces tissue damage via local effects of neutrophils. Initial clinical trials using standard donor GC in a strictly extracorporeal bioreactor system for treatment of septic shock patients already provided evidence for beneficial effects with fewer side effects, by separating patient and donor immune cells using plasma filters. In this ex vivo study, we demonstrate the functional characteristics of a simplified extracorporeal therapy system using purified granulocyte preparations. Methods Purified GC were used in an immune cell perfusion model prefilled with human donor plasma simulating a 6-h treatment. The extracorporeal circuit consisted of a blood circuit and a plasma circuit with 3 plasma filters (PF). PF1 is separating the plasma from the patient’s blood. Plasma is then perfused through PF2 containing donor immune cells and used in a dead-end mode. The filtrated plasma is finally retransfused to the blood circuit. PF3 is included in the plasma backflow as a redundant safety measure. The donor immune cells are retained in the extracorporeal system and discarded after treatment. Phagocytosis activity, oxidative burst and cell viability as well as cytokine release and metabolic parameters of purified GCs were assessed. Results Cells were viable throughout the study period and exhibited well-preserved functionality and efficient metabolic activity. Course of lactate dehydrogenase and free hemoglobin concentration yielded no indication of cell impairment. The capability of the cells to secret various cytokines was preserved. Of particular interest is equivalence in performance of the cells on day 1 and day 3, demonstrating the sustained shelf life and performance of the immune cells in the purified GCs. Conclusion Results demonstrate the suitability of a simplified extracorporeal system. Furthermore, granulocytes remain viable and highly active during a 6-h treatment even after storage for 3 days supporting the treatment of septic patients with this system in advanced clinical trials.

Background Immune cell dysfunction is a central part of immune paralysis in sepsis. Granulocyte concentrate (GC) transfusions can induce tissue damage via local effects of neutrophils. The hypothesis of an extracorporeal plasma treatment with granulocytes is to show beneficial effects with fewer side effects. Clinical trials with standard GC have supported this approach. This ex vivo study investigated the functional properties of purified granulocyte preparations during the extracorporeal plasma treatment. Methods Purified GC were stored for up to 3 days and compared with standard GC in an immune cell perfusion therapy model. The therapy consists of a plasma separation device and an extracorporeal circuit. Plasma is perfused through the tubing system with donor immune cells of the GC, and only the treated plasma is filtered for re‐transfusion. The donor immune cells are retained in the extracorporeal system and discarded after treatment. Efficacy of granulocytes regarding phagocytosis, oxidative burst as well as cell viability and metabolic parameters were assessed. Results In pGC, the metabolic surrogate parameters of cell functionality showed comparable courses even after a storage period of 72 h. In particular, glucose and oxygen consumption were lower after extended storage. The course of lactate dehydrogenase concentration yields no indication of cell impairment in the extracorporeal circulation. The cells were viable throughout the entire study period and exhibited preserved phagocytosis and oxidative burst functionality. Conclusion The granulocytes demonstrated full functionality in the 6 h extracorporeal circuits after 3 days storage and in septic shock plasma. This is demonstrating the functionality of the system and encourages further clinical studies.