Red blood cell supernatant potentiates LPS-induced proinflammatory cytokine response from peripheral blood mononuclear cells

Abstract

Allogeneic blood transfusion has an immunomodulatory capacity on its recipients through accumulation of immunologically active substances with blood storage, and prestorage leukoreduction reduces many of these mediators. We investigated lipopolysaccharide (LPS)-induced cytokine response of peripheral blood mononuclear cells (PBMCs) exposed to packed red blood cell (PRBC) supernatants from leukoreduced (LR) or non-leukoreduced (NLR) units with variable duration of storage. PRBC units were collected with or without leukoreduction on Day 0 before routine storage. The plasma fraction (supernatant) was isolated from LR and NLR units after 1 day (D1) or 42 days (D42) of storage and exposed to PBMCs versus control media for 24 h, then with LPS for an additional 24 h. Cell supernatants were analyzed for IL-1beta, IL-6, IL-8, IL-10, and TNF-alpha by cytokine bead array. IL-1beta, TNF-alpha, and IL-6 were significantly elevated in PRBC groups versus control. D42 NLR PRBC supernatant significantly increased secretion of IL-1beta and IL-6 compared to D1 NLR PRBC supernatant. LR significantly attenuated the cytokine response of IL-1beta. Thus, PRBC supernatant potentiates proinflammatory LPS-induced cytokine secretion from PBMCs. This response is accentuated with storage duration and partially attenuated with leukoreduction. These findings may partially explain the immune activation seen clinically after blood transfusion.

FIG. 1.

PRBC supernatant potentiates LPS-induced proinflammatory cytokine release by PBMCs. (A) The amount of IL-1β secreted from PBMCs exposed to control media, Day 1 non-leukoreduced PRBC supernatant (D1 NLR), or Day 42 non-leukoreduced PRBC supernatant (D42 NLR) is shown as a scatter plot with the mean represented by a bar. D42 NLR PRBC supernatant significantly increased IL-1β secretion versus control and D1 NLR supernatant (*P < 0.05 vs. Ctl and D1 NLR; n = 4 for control, n = 15 for D1 NLR and n = 16 for D42 NLR). (B) D42 NLR supernatant exposure resulted in increased TNF-α versus control and significantly increased IL-6 (C) versus control and D1 NLR PRBC supernatant (*P < 0.05 vs. Ctl and D1 NLR groups). (D) IL-10 levels were not different between groups.

FIG. 2.

Leukoreduction attenuates proinflammatory cytokine secretion by LPS-stimulated PBMCs. (A) The amount of IL-1β secreted from PBMCs exposed to control Day 42 non-leukoreduced PRBC supernatant (D42 NLR) and Day 42 leukoreduced PRBC supernatant (D42 LR) is shown as a scatter plot with the mean represented as a bar. D42 LR PRBC supernatant significantly decreased IL-1β secretion versus D42 NLR supernatant (*P < 0.05 vs. D42 NLR group; n = 16 for D42 NLR, n = 12 for D42 LR). D42 LR supernatant exposure resulted in nonsignificant reductions in (B) TNF-α and (C) IL-6 secretion. (D) IL-10 levels were not altered.