Stored Red Blood Cell Transfusion Induces Regulatory T Cells

Abstract

BACKGROUND Allogeneic blood transfusion mediates immunosuppression in transfused recipients by an unknown mechanism. Regulatory T cells (Tregs) are suppressive CD4+CD25+Foxp3+ cells with a central role in immunosuppression in trauma victims, cancer patients, and transplant recipients. We hypothesized that transfusion-related immunosuppression is, in part, mediated by induction of Tregs, and this induction is attenuated with prestorage leukoreduction and accentuated with prolonged storage. STUDY DESIGN Packed red blood cell (PRBC) units were obtained and 50% of PRBCs were leukoreduced (LR) before routine storage for 1 day or 42 days and the supernatant was collected. Normal human peripheral blood mononuclear cells (PBMCs) were exposed to 1-day NLR, 42-day NLR, 1-day LR, or 42-day LR PRBC supernatants or to PRBC storage solution or washed PRBC supernatant ± anti-CD3 stimulation, and analyzed by flow cytometry for Foxp3+ Tregs or CD25+-activated T cells. PRBC supernatants and cell culture supernatants were analyzed by immunoassay for interleukin (IL)-1β, IL-2, IL-4, IL-10, interferon-γ, tumor necrosis factor–α, and transforming growth factor–β. Treg activity was evaluated by suppression assay. RESULTS All PRBC groups induced Tregs compared with control media in anti–CD3-stimulated PBMCs, without alteration by LR or prolonged storage. PRBC supernatant did not alter nonspecific T-cell activation from control media. PRBC-induced Tregs were suppressive, inhibiting proliferation of T-responder cells. All cytokines measured decreased with storage in LR PRBC units and no cytokines were substantially elevated in cell supernatants exposed to PRBC supernatant. PRBC storage solution did not reproduce the effects of PRBC supernatant, and washed PRBC supernatant attenuated Treg induction. CONCLUSIONS PRBC supernatant induces Tregs, but this induction is not altered by LR or prolonged storage. This induction appears to be independent of cytokines and is attenuated with washed PRBCs, implicating the plasma fraction.

Blood Storage Duration and Biochemical Recurrence of Cancer After Radical Prostatectomy

“…23,32 Regulatory T cells promote immune tolerance, prevent autoimmunity, suppress cellmediated cytotoxicity, and inhibit the function of dendritic cells. [33][34][35] Baumgartner et al 36 demonstrated that the supernatant from stored peripheral RBCs induced regulatory T cells; however, the induction was not affected by the storage age of the RBCs. Blood transfusions may impair the natural immune-killing function of the body against growing and metastasizing cancer cells.…”

Characterisation of dendritic cell immune profile in models of transfusion

“…I found minimal modulation of cytokine responses following exposure to PRBC alone, however, both mDC and BDCA3 + DC responses to polyI:C and LPS were suppressed in the presence of PRBC. Together poor co-stimulation and lack of cytokine and chemokine production may be associated with inadequate T and B lymphocyte responses [79,80,88] and my data suggest PRBC transfusion has the potential to impair downstream lymphocyte responses.…”

“…In one study, T lymphocyte activation (CD25 + ) was not significantly affected following exposure to PRBC supernatants [85]. However, in another study PRBC supernatants increased the number of regulatory T lymphocytes (CD25 + Treg) and reduced the number of T responder lymphocytes (CD25 -) [79]. A more recent study indicates B and T lymphocyte proliferation was suppressed following exposure to leukodepleted PRBC stored for two to three weeks, but not freshly collected leukodepleted RBC [88].…”

“…The potential for PRBC to modulate recipients' immune response and impact patient outcomes has been studied using in-vitro [79][80][81][82][83][84][85][86][87][88][89] and in-vivo [90] models. An in-vitro study using a whole blood model reported increased interleukin (IL)-10 production and reduced tumour necrosis factor (TNF)-α production by the overall leukocytes in the culture supernatant following 24 h exposure to either autologous or allogeneic PRBC [81].…”

“…Increased monocyte erythrophagocytosis of stored PRBC has also been reported [283]. Transfusion-related modulation of immune responses are not limited to innate cells, with exposure to PRBC reported to increase CD25 + regulatory T lymphocyte production, reduce the number of responder T lymphocytes [79], and suppress B and T lymphocyte proliferation [80,88]. To date, studies assessing the role of DC in transfusion outcomes are limited.…”