Induction of Immune Tolerance by Macrochimerism: Preliminary Study for Overcome of Islet Allograft Rejection

Hong, Oak Kee; Kim, Sung Joo; Park, Chung Gyu; Chung, Chul Woo; Kwon, Hyuk Sang; Choi, Yoon Hee; Cha, Bong Yun; Son, Ho Yong; Yoon, Kun Ho

Abstract

BACKGROUND: Recently islet transplantation(TPx) has achieved remarkable results while it is not the ultimate solution yet because of a serious shortage of human pancreases, immune rejection and recurrence of autoimmunity. Immune tolerance induction is one of the ideal way for overcome the immune rejection and recurrence of autoimmunity after islet TPx. In this study, we tested the efficacy of the mixed chimerism conducted by minimally invasive regimens on induction of immune tolerance in allogenic skin transplantation model.
METHODS
Busulfan(600microgram/mouse) was administered on day -1, and 0.1 mg monoclonal antibody against CD45RB and 0.5 mg monoclonal antibody against CD154 were administered intraperitoneally on days 0, 2, 4, and 6. We gave the C57BL/6 recipients either a standard-dose(2x107 bone marrow cells/mouse; SBMT-Ig) or a high-dose(20x107 bone marrow cells/mouse; HBMT-Ig) of bone marrow from BALB/c donors. After transplantation the, C57BL/ 6 recipients received BALB/c donor skin grafting on day 0. Untreated control animals in each group, both the SBMT and HBMT mice(without busulfan) were treated with marrow cells only, and they received transplanted skin grafts from the BALB/c donor on day 0. We monitored chimerism by flow cytometry and we monitored tolerance by skin grafting.
RESULTS
Chimerism was significantly increased in all the groups and it peaked on day 56 after bone marrow transplantation. On day 56, chimerism in the peripheral blood did not significantly differ between the SBMT(15.0+/-3.6%) mice and the HBMT+Ig(15.3+/-6.5%) mice. Allogenic skin transplanted on the untreated mice was invariably lost within 20 days, with a mean survival time of 10.0+/-2.5 days for the SBMT mice and 13.3+/-4.9 days for HBMT mice. The skin survival rates were significantly greater for the SBMT+Ig mice(39.0+/-36.6days) and for the HBMT+Ig mice(79.9+/-43.6 days)(HBMT+Ig vs. SBMT P=0.006: HBMT+Ig vs. SBMT+Ig P=0.0087: HBMT+Ig vs. HBMT P=0.0093). Although three of the eight(37.5%) HBMT+Ig mice showed a high skin graft survival rate >120 days, the chimerism was 3.4+/-1.3% in the peripheral blood. In the HBMT+Ig mice, chimerism was higher in the thymus(8.05+/-9.7%) than in the peripheral blood and it was significantly higher than in the thymus of the HBMT mice(0.36+/-0.5%)(P< 0.05).
CONCLUSIONS
These data shows that chimerism created by minimally invasive method with high-dose bone marrow and anti-CD45RB/CD154 antibody seems promissing way for prolongation of islet allograft survival