Response of Allogeneic Mononuclear Cells to Stored Red Cell Concentrates

Abstract

Red blood cell (RBC) transfusion has been implicated in certain adverse patient outcomes. Immunomodulation may play a central role. The aim of this project was to determine the ability of supernatants and cellular fractions of RBC concentrates to modulate the immune response of allogeneic mononuclear cells (MNCs), particularly monocytes. Non-leucocytereduced, buffy-coat-depleted and leucocyte-filtered RBC concentrates were prepared and stored according to standard blood bank procedures. RBC samples were collected on day 1 and fortnightly until product expiry, and centrifuged to obtain supernatant and cellular fractions. On the day of RBC sample collection, whole blood (WB) and MNCs were prepared from ABO-compatible allogeneic donors. Induction of monocyte CD11b and CD54 was determined by flow cytometry by incubating allogeneic WB with RBC supernatants or cellular fractions, followed by staining with fl uorescently-labelled anti-CD14, anti-CD11b and anti-CD54. Cytokine release was determined by incubating MNCs with RBC supernatants and culture supernatants were assessed by ELISA for IL-8, TNFalpha; and IL-10. Supernatant and cellular fraction from non-leucocyte-reduced RBC concentrates induced expression of CD11b and CD54 on allogeneic monocytes. Buffy-coatdepleted and leucocyte-filtered RBC concentrates had minimal effect on monocyte CD11b or CD54 expression. Cytokine release from MNCs incubated with RBC supernatant suggested a tenuous balance between proinflammatory (IL-8 and TNF alpha;) and immunosuppressive (IL-10) responses. All RBC product types induced cytokine release from MNCs. The results from this study indicate that stored RBC concentrates can modulate allogeneic MNCs. Both proinflammatory and immunosuppressive responses were evident. Leucocytes in RBC concentrates appear to favour a proinflammatory response by MNCs.