Enhancement of nonspecific resistance by liposome-encapsulated immunomodulators does not affect skin graft rejection in mice

Administration of liposome-encapsulated immunomodulating agents muramyl tripeptide phosphatidyl ethanolamine (LE-MTPPE) or interferon-gamma (LE-IFN-gamma), or co-encapsulated MTPPE and IFN-gamma (LE-(MTPPE/IFN-gamma)) resulted in a dramatic increase of the nonspecific antimicrobial resistance in mice, as shown before. This kind of treatment is especially of use in immunocompromised hosts who are prone to severe infections. Application of these immunomodulators might protect these patients, e.g., transplant recipients, from opportunistic infections. However, accelerated rejection of the graft, resulting from augmentation of the antimicrobial defense in a nonspecific way, has to be avoided. In this study, the effect of treatment with LE-MT-PPE, LE-IFN-gamma, or LE-(MTPPE/IFN-gamma) on skin graft rejection in mice was investigated. It was found that prophylactic treatment of skin-grafted mice with immunomodulating formulations did not influence rejection of the graft. Moreover, in T cell-depleted mice, which showed a prolonged graft survival compared with immunocompetent recipients, the administration of immunomodulators did not change the survival time of the grafts compared with T cell-depleted mice that did not receive immunomodulators. The results clearly show that, in this experimental setting, application of the antimicrobial resistance-enhancing formulations (LE-MTPPE, LE-IFN-gamma, and LE-(MTPPE/IFN-gamma)) is allowed in graft-bearing recipients, without influencing graft survival.