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*
Laboratory of Molecular Immunology and
Pulmonary and Critical Care Division, Department of Medicine, and
Department of Pathology, Brigham and Womens Hospital, Harvard Medical School, Boston, MA 02115
TNF-
and lymphotoxin (LT)
have been shown to be important
mediators of allograft rejection. TNF-R1 is the principal receptor for
both molecules. Mice with targeted genetic deletions of TNF-R1
demonstrate normal development of T and B lymphocytes but exhibit
functional defects in immune responses. However, the role of
TNF-R1-mediated signaling in solid organ transplant rejection has not
been defined. To investigate this question, we performed vascularized
heterotopic allogeneic cardiac transplants in TNF-R1-deficient
(TNF-R1-/-) and wild-type mice. Because all allografts in
our protocol expressed TNF-R1, direct antigraft effects of TNF-
and
LT
were not prevented. However, immunoregulatory effects on
recipient inflammatory cells by TNF-R1 engagement was eliminated in
TNF-R1-/- recipients. In our study, cardiac allograft
survival was significantly prolonged in TNF-R1-/-
recipients. Despite this prolonged allograft survival, we detected
increased levels of CD8 T cell markers in allografts from
TNF-R1-/- recipients, suggesting that effector functions,
but not T cell recruitment, were blocked. We also demonstrated the
inhibition of multiple chemokines and cytokines in allografts from
TNF-R1-/- recipients including RANTES,
IFN-inducible protein-10, lymphotactin, and IL-1R antagonist, as
well as altered levels of chemokine receptors. We correlated gene
expression with the physiologic process of allograft rejection using
self-organizing maps and identified distinct patterns of gene
expression in allografts from TNF-R1-/- recipients. These
findings indicate that in our experimental system TNF-
and LT
exert profound immunoregulatory effects through
TNF-R1.
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