Effects of lipopolysaccharide on the induction of mixed chimerism in cyclophosphamide-induced tolerance.
Cyclophosphamide (CP)-induced tolerance is a mixed chimerism-based tolerance and is one of the strategies used to induce transplant tolerance. Toll-like receptor (TLR) agonists are reportedly able to abrogate the induction of tolerance by activating alloreactive T cells, or by inhibiting Treg cells. However, little is known about the effect of the immune response mediated by TLR on mixed chimerism-based tolerance protocols. In this study, we evaluated the influence of lipopolysaccharide (LPS), which is best known as an TLR4 agonist, on CP-induced tolerance. BALB/c (H-2(d)) mice received a conditioning regimen consisting of 10(8) donor DBA/2 (H-2(d)) spleen cells (SC) on day 0 and 200 mg/kg CP on day 2. A single dose of 20 microg LPS was injected on day -2, 0, 7, or 35. Our results showed that LPS infusion at any time point resulted in chronic rejection of donor skin grafts and the abrogation of mixed chimerism in 33-60% of recipients. We found a correlation between skin graft acceptance and higher levels of mixed chimerism. Flow cytometric analysis revealed that donor-reactive T cells were permanently eliminated, regardless of LPS infusion. In conclusion, LPS-infusion had little influence on the immune response of donor-reactive T cells, but had a significant effect on the induction and maintenance of mixed chimerism in CP-induced tolerance.
Onzuka
T
T
Department of Cardiovascular Surgery, Faculty of Medicine, Kyushu University, Higashi-ku, Fukuoka, Japan.
Tomita
Y
Y
Shimizu
I
I
Okano
S
S
Yamada
H
H
Yoshikai
Y
Y
Tominaga
R
R
D000818:Animals; D046528:Chimerism; D003520:Cyclophosphamide / Q000494:pharmacology*; D005434:Flow Cytometry; D006084:Graft Rejection / Q000276:immunology; D006085:Graft Survival / Q000276:immunology; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D016038:Skin Transplantation / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology; D023001:Transplantation Tolerance / Q000276:immunology*
D007166:Immunosuppressive Agents; D008070:Lipopolysaccharides; D003520:Cyclophosphamide