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Transplantation:
doi: 10.1097/TP.0b013e31829b07b5
Basic and Experimental Research

Galectin-9 in Combination With Rapamycin Induces Cardiac Allograft Tolerance in Mice

Cai, Lanjun1,2; Zhou, Hongmin3; Fang, Zemin3; Yuan, Jin4; Niki, Toshiro5; Hirashima, Mitsuomi6; He, Wentao7,8; Chen, Zhonghua Klaus1,8

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Abstract

Background

Galectin-9 serves opposing roles in the innate and adaptive immune systems. Galectin-9 triggers T-cell immunoglobulin mucin-3 (Tim-3) on T helper type 1 (Th1) cells, thereby terminating Th1 immunity and protecting allografts from host immune attacks. Meanwhile, galectin-9 promotes the maturation of dendritic cells (DCs) that deliver proinflammatory signals. We previously showed that galectin-9 significantly prolongs cardiac allograft survival in mice but failed to induce tolerance. This study aimed at improving the administration protocol to induce allograft tolerance. We examined whether rapamycin can reverse the proinflammatory effects of galectin-9 on DCs and whether rapamycin synergizes with galectin-9 to induce cardiac allograft tolerance.

Methods

Monocytes/DCs from cardiac allografts were assessed for Tim-3 expression by flow cytometry. Costimulatory molecules CD80/CD86 were measured on galectin-9/rapamycin–treated bone marrow–derived DCs by flow cytometry. We performed heterotopic cervical cardiac transplantation using BALB/c donors and C57BL/6 recipients and assessed graft survival time. T cells of long-term surviving recipients were immunoassayed for interferon-γ and interleukin-4 secretion.

Results

Allograft-infiltrating monocytes/DCs expressed high Tim-3 levels (47.3%±5.6%). Expression of CD80/CD86 was up-regulated on galectin-9–treated bone marrow–derived DCs, which was reversed by rapamycin. Combined treatment with galectin-9 and rapamycin promoted the permanent acceptance of fully mismatched grafts (survival time >180 days; n=6). However, treatment with galectin-9 or rapamycin alone was not sufficient to induce tolerance. Galectin-9/rapamycin–induced tolerance was associated with low donor-specific interferon-γ and interleukin-4 secretion.

Conclusions

Rapamycin inhibits proinflammatory effects of galectin-9 on DCs. Combined treatment of galectin-9 and rapamycin promotes allografts tolerance, which is associated with reduced Th1 and Th2 responses.

Copyright © 2013 by Lippincott Williams & Wilkins

 

 

 

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