Chemokine and toll-like receptor signaling in macrophage mediated islet xenograft rejection.
BACKGROUND
Adoptive transfer of antigen-primed T-cell-activated macrophages into NOD-SCID mice within 14 days of foetal porcine pancreatic fragment (FPP) or foetal porcine skin (FPS) transplantation had been shown to cause xenograft rejection. In the present study, it was proposed that signaling between the graft and macrophages promoted specific graft recognition and destruction in this setting.


METHODS
Exogenous macrophages isolated from rejecting FPP xenografts were transferred to NOD-SCID FPP recipients and tracked by Ly5.1 surface antigen or via CSFE staining. Monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1alpha (MIP-1alpha), macrophage inflammatory protein-1beta (MIP-1beta), regulated upon activation, normal T-cell expressed and secreted (RANTES), chemokine (C-C motif) receptor 2 (CCR2), chemokine (C-C motif) receptor 5 (CCR5), toll-like receptors (TLRs) (1-9) and gene expression in transplanted FPP xenografts was evaluated by real-time polymerase chain reaction. Gene expression of CCR2, CCR5 and TLRs was also analyzed in pooled samples of activated and non-activated macrophages.


RESULTS
Exogenous macrophages were shown to track to and reject recently transplanted but not established FPP xenografts. Gene expression for MCP-1, RANTES, MIP-1alpha and MIP-1beta was at least 3-fold greater in recently transplanted compared with established xenografts (P < 0.05), and CCR2 and CCR5 gene expression was 10-fold greater in activated compared non-activated macrophages, suggesting that graft-mediated pro-inflammatory signals were important for macrophage recruitment. Specific graft recognition by macrophages may involve TLR signaling as macrophages exposed to porcine islets had higher levels of TLR gene expression compared with those exposed to allografts regardless of the level of activation.


CONCLUSIONS
Xenografts provide additional activation signals to macrophages that are not seen following allotransplantation. This study identifies chemokines and TLR as important signals in macrophage-mediated recognition and rejection of islet xenografts.
Chandra
Abhilash P
AP
Centre for Transplant and Renal Research, Westmead Millenium Institute, University of Sydney at Westmead Hospital, Westmead, Australia.
Ouyang
Li
L
Yi
Shounan
S
Wong
Jeffrey K W
JK
Ha
Hong
H
Walters
Stacey N
SN
Patel
Anita T
AT
Stokes
Rebecca
R
Jardine
Meg
M
Hawthorne
Wayne J
WJ
O'Connell
Philip J
PJ
D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002465:Cell Movement; D018925:Chemokines / Q000276:immunology / Q000378:metabolism*; D005260:Female; D015870:Gene Expression; D006084:Graft Rejection / Q000276:immunology* / Q000378:metabolism; D016381:Islets of Langerhans Transplantation / Q000009:adverse effects / Q000276:immunology* / Q000473:pathology; D008264:Macrophages / Q000166:cytology / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D054390:Receptors, CCR2; D019713:Receptors, CCR5 / Q000235:genetics / Q000276:immunology; D019707:Receptors, Chemokine / Q000235:genetics / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology*; D012867:Skin / Q000276:immunology / Q000378:metabolism; D013552:Swine; D051193:Toll-Like Receptors / Q000235:genetics / Q000378:metabolism*; D014183:Transplantation, Heterologous / Q000276:immunology*; D015854:Up-Regulation
C515335:Ccr2 protein, mouse; D018925:Chemokines; D054390:Receptors, CCR2; D019713:Receptors, CCR5; D019707:Receptors, Chemokine; D051193:Toll-Like Receptors