Safety Evaluation for a Cell-based Immune Support System in an Ex Vivo Rat Model of Gram-negative Sepsis

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.