Induction of unresponsiveness to islet xenograft by MMC treatment of graft and blockage of LFA-1/ICAM-1 pathway.
BACKGROUND
Induction of unresponsiveness to graft is one of major interest in xenotransplantation. Two different modalities [direct graft treatment by mitomycin C (MMC) and blockage of the lymphocyte function-associated antigen-1/intracellular adhesion molecule-1 (LFA-1/ICAM-1) pathway in recipients by species-specific mAbs] were tested for their ability to produce unresponsiveness to secondary islet xenografts.


METHODS
Collagenase-digested WS (RT1k) rat islets, purified by Ficoll density gradient, were incubated for 30 min with MMC 10 microg/ml, cultured for 20 hr, and transplanted into the renal subcapsular space of streptozotocin-induced diabetic C57BL/6 (H-2b) mice. Recipient mice were divided into experimental groups according to anti-rat ICAM-1 and/or anti-mouse LFA-1 mAb treatment and transplantation of MMC-treated or nontreated islets.


RESULTS
MMC pretreatment alone prolonged graft survival, with a mean survival time (MST) of 23.0+/-7.4 days, compared with that of cultured islets (12.4+/-2.7 days; P<0.01). MMC treatment of islets significantly augmented graft survival, compared with that of crude islet grafts under treatment with anti-donor ICAM-1 mAb (MST: >41.3+/-30 vs. 16.6+/-5.4 days, P<0.01), anti-recipient LFA-mAb (MST: >70.3+/-28.9 vs. 30.4+/-10.4 days, P<0.001), or both mAbs (MST: >88.1+/-24.1 vs. 23+/-7.4 days, P<0.0001). One of six, four of nine, and six of eight animals accepted MMC-treated islet xenografts over 100 days after treatment with anti-rat ICAM-1, anti-mouse LFA-1, or both mAbs treatments, respectively, whereas none of the animals accepted nontreated islets under the same treatment. When the mice bearing long-term functioning xenografts were challenged with the secondary graft from the original donor strain, the animals previously treated with anti-recipient LFA-1 and anti-donor ICAM-1 mAbs were more prone to accept it than animals given anti-recipient LFA-1 mAb alone (MST: 55.8+/-25.7 vs. 15+/-2.4 respectively; P<0.001), although they rejected the third-party xenograft and allograft acutely.


CONCLUSIONS
In the xenogeneic islet transplantation model, MMC graft pretreatment and blockage of the ICAM-1/LFA-1 pathway constitute a potent protocol for inducing unresponsiveness to islet xenografts.
Grochowiecki
T
T
Department of Surgery II, Biomedical Research Center, Osaka University Medical School, Japan.
Gotoh
M
M
Dono
K
K
Takeda
Y
Y
Sakon
M
M
Yagita
H
H
Okumura
K
K
Miyasaka
M
M
Monden
M
M
D000818:Animals; D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D003921:Diabetes Mellitus, Experimental / Q000601:surgery; D004359:Drug Therapy, Combination; D006085:Graft Survival / Q000187:drug effects; D018799:Intercellular Adhesion Molecule-1 / Q000276:immunology*; D016381:Islets of Langerhans Transplantation / Q000276:immunology*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000276:immunology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D016685:Mitomycin / Q000627:therapeutic use*; D051381:Rats; D011919:Rats, Inbred Strains; D014183:Transplantation, Heterologous / Q000276:immunology*
D000911:Antibodies, Monoclonal; D016169:Lymphocyte Function-Associated Antigen-1; D018799:Intercellular Adhesion Molecule-1; D016685:Mitomycin