Requirement of MyD88 for macrophage-mediated islet xenograft rejection after adoptive transfer.
BACKGROUND
Porcine antigen primed and CD4+ T-cell activated macrophages are able to migrate to and destroy porcine xenografts. However, the specific signaling mechanisms involved remain to be identified.


METHODS
In this study macrophages which lack the universal toll-like receptor (TLR) adaptor MyD88 were used to investigate the role of TLR in the recognition and activation of macrophages in islet xenograft rejection. Macrophages were isolated from rejecting MyD88(-/-) and wild-type C57BL/6 mice that were recipients of neonatal porcine pancreatic cell cluster (NPCC) xenografts, and were transferred to NPCC recipient NOD-SCID mice.


RESULTS
Both wild-type C57BL/6 and MyD88(-/-) mice rejected NPCC xenografts 8 and 10 days, respectively after transplantation, and the grafts were heavily infiltrated with CD4+ T cells and macrophages. However, graft infiltrating macrophages from rejecting MyD88(-/-) recipients demonstrated impaired up-regulation of TLR expression and impaired activation phenotype, when compared to those from rejecting C57BL/6 recipients. Transfer of NOD-SCID recipients with macrophages from rejecting C57BL/6 mice resulted in NPCC xenograft rejection along with massively infiltrated macrophages 8 days after transfer, whereas NPCC xenografts in NOD-SCID mice transferred with macrophages from rejecting MyD88(-/-) mice remained intact until the end of this study, 90 days after transfer, with insulin-positive islets and no infiltration by macrophages.


CONCLUSIONS
This study demonstrates that deletion of MyD88 causes impaired macrophage activation after pig islet xenotransplantation. However, graft survival is not prolonged and xenografts are rejected rapidly by alternate mechanisms.
Yi
Shounan
S
Center for Transplant and Renal Research, Westmead Millennium Institute, University of Sydney at Westmead Hospital, Westmead, Australia. shounan_yi@wsahs.nsw.gov.au
Wang
Ying
Y
Chandra
Abhilash P
AP
O'Hara
Jennifer M
JM
Wu
Jingjing
J
Ouyang
Li
L
Burgess
Jane S
JS
Hawthorne
Wayne
W
Wu
Huiling
H
Chadban
Steven J
SJ
O'Connell
Philip J
PJ
D019264:Adoptive Transfer; D000818:Animals; D005260:Female; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D006084:Graft Rejection / Q000276:immunology*; D016381:Islets of Langerhans Transplantation / Q000276:immunology / Q000473:pathology / Q000502:physiology*; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D016133:Polymerase Chain Reaction; D013552:Swine; D051193:Toll-Like Receptors / Q000502:physiology; D014183:Transplantation, Heterologous / Q000473:pathology*
D053594:Myeloid Differentiation Factor 88; D051193:Toll-Like Receptors