Characterisation of dendritic cell immune profile in models of transfusion

Abstract

Blood transfusion modulates recipients' immune responses sometimes resulting in poor clinical outcomes. Further, transfusion with blood products at date-of-expiry has been associated with exacerbation of this concerning problem. In-vitro studies have demonstrated exposure to packed red blood cell (PRBC) and platelet products modulate the responses of leukocytes, however, there are limited studies on the impact of transfusion on dendritic cells (DC). Despite DC being central to the immune response, their role in transfusion-related immune modulation remains largely undefined. I hypothesised that exposure to blood components changes DC phenotype and function, which could be one mechanism underpinning transfusion-related immune modulation. The potential for blood components (PRBC, buffy-coat-derived platelet concentrates (PC) and cryopreserved platelets (cryo-PLT)) to modulate responses of myeloid dendritic cells ii whether blood components exposing F-actin for Clec9A ligation were present within the blood product. rhClec9A did not bind fresh or stored PRBC, and this outcome was supported by the lack of detection of F-actin. Although, no binding of rhClec9A to PC or cryo-PLT was demonstrated, F-actin was detected on both types of platelet products. As binding of rhClec9A to PRBC, PC or cryo-PLT was not detected, EDTA blood collection tubes were used for the remainder of the study under the premise that lack of expression of this receptor would not impact on outcomes in my transfusion models.I assessed the impact of fresh and/or stored blood products on mDC and BDCA3 + DC surface antigen and inflammatory profile using a human in-vitro whole blood model of transfusion. In parallel, to model the processes associated with viral or bacterial infection, polyinosinic:polycytidylic acid (polyI:C) or lipopolysaccharide (LPS) was added respectively. Exposure to PRBC and PC predominately suppressed surface antigen expression (CD40, CD80, CD83 and CD86) and inflammatory mediator production (interleukin (IL)-6, IL-8, IL-12, tumour necrosis factor-α and interferon-gamma inducible protein-10 or IL-10) on both DC subsets. These changes were often more evident in the presence of polyI:C and LPS, and when DC were exposed to stored PRBC. Similar modulation was evident for BDCA3 + DC when exposed to cryo-PLT alone and cryo-PLT in the presence of polyI:C and LPS. The impact of blood transfusion on the overall inflammatory response by leukocytes was also examined. The immunomodulatory effect of transfusion in-vitro was more pronounced in the presence of polyI:C and LPS. For PRBC, an additional erythrophagocytosis assay was conducted where the uptake of stored PRBC by mDC and BDCA3 + DC was significantly increased in comparison to fresher PRBC.This study provided the first evidence that exposure of PRBC, PC and cryo-PLT modulates mDC and/or BDCA3 + DC maturation and activation. The changes were more pronounced when modelling processes associated with concurrent viral or bacterial infection.Experimental evidence suggested that mod...