Neutrophilic granulocytes are the predominant cell type infiltrating pancreatic islets in contact with ABO-compatible blood

Abstract

SummaryThe poor outcome of intraportal islet transplantation may be explained by the instant blood-mediated inflammatory reaction (IBMIR), characterized by islet entrapment in blood clots, leucocyte infiltration and disruption of islet morphology. Here we employ a newly developed in vitro system to identify the blood cells involved in this process. Islets were mixed with ABO-compatible blood in heparinized tubes and incubated for various times up to 6 h. Clots were analysed immunohistochemically for detection of platelets (CD41a), leucocytes/lymphocytes (CD11b), granulocytes (CD16, lysozyme), neutrophilic granulocytes (neutrophil elastase), eosinophilic granulocytes (NaCN + + + + H 2 O 2 ), macrophages (CD68), dendritic cells (CD209/DC-SIGN), B cells (CD20) and T cells (CD4, CD8). Platelets were rapidly deposited around the islets in contact with the blood, reaching a maximum by 30 min. The first neutrophilic granulocytes appeared in the islets after 15 min, increased at 1 h and peaked at 2 h. Small numbers of macrophages were found infiltrating the islets already after 5 min, with a slight increase over time. However, control stainings of cultured islets and pancreas biopsies identified these cells as being largely of donor origin. No T cells, B cells, dendritic cells or eosinophilic granulocytes were detected during the 6 h observation time. Neutrophilic granulocytes were identified as the main infiltrating blood cell in islets exposed to blood, implying that these cells play a key role in clinical islet transplantation. Because islets are known to be exquisitely susceptible to oxidative stress, development of drugs targeting neutrophilic cytotoxicity could markedly improve the outcome of islet transplantation.

Tirofiban and Activated Protein C Synergistically Inhibit the Instant Blood Mediated Inflammatory Reaction (IBMIR) from Allogeneic Islet Cells Exposure to Human Blood

“…Immunohistochemisty showed that islets were infiltrated by neutrophils ( Figure 1D), which was consistent with previous reports of a similar assay (18), and islets contained within the clots demonstrated widespread staining for C4d implicating complement-mediated cell lysis as a feature of IBMIR ( Figure 1G). …”

Tissue Factor Knockdown in Porcine Islets: An Effective Approach to Suppressing the Instant Blood-Mediated Inflammatory Reaction

“…Infusion of islet cells expressing TF into the portal vein tion (IBMIR) (2,19), which is characterized by coagulation and complement activation that leads to platelet triggers IBMIR, leading to the activation of coagulation pathway and the production of thrombin (16,24,29,31). consumption and neutrophil infiltration of the islets (25,37), and may even be stronger in the xenograft setCollectively, these data suggest the importance of TF expression by islets in regulating IBMIR. ting due to species barrier (4,33).…”

CXCR1/2 inhibition enhances pancreatic islet survival after transplantation

“…The identification of a targetable pathway able to prevent the recruitment of both these cells is an important finding. PMNs are the predominant cell type infiltrating the islets in experimental models (14), and a vicious cycle mediated by NKT and PMN IFN-γ-based cross-talk was recently demonstrated to be harmful to transplanted islets (15). Concordantly, NKT cell inhibition or deletion improves engraftment and delays islet rejection (1, 2, 15).…”