Cytokines Regulate the Pattern of Rejection and Susceptibility to Cyclosporine Therapy in Different Mouse Recipient Strains After Cardiac Allografting

Abstract

We determined the role of cytokines in regulating the pattern of rejection and recipient susceptibility to cyclosporine (CsA) in a mouse cardiac allograft model. Hearts from C3H mice transplanted into untreated BALB/c (Th2-dominant) and C57BL/6 (Th1-dominant) mice showed different patterns of rejection. C3H allografts in BALB/c mice showed typical acute vascular rejection (AVR) with strong intragraft deposition and high serum levels of anti-donor IgG with predominant IgG1, while C3H allografts in C57BL/6 mice showed typical acute cellular rejection (ACR) with massive intragraft infiltration of CD4+ and CD8+ lymphocytes and low serum levels of anti-donor IgG with predominant IgG2a. Elevated intragraft mRNA expression of IL-2, IFN-γ, and IL-12 mRNA was present in C57BL/6 recipients, whereas allografts in BALB/c mice displayed increased IL-4 and IL-10 mRNA levels. CsA therapy completely inhibited ACR and induced indefinite allograft survival in C57BL/6 recipients, while the same therapy failed to prevent AVR, and only marginally prolonged graft survival in BALB/c recipients. In contrast, rapamycin blocked AVR, achieving indefinite survival in BALB/c recipients, but was less effective at preventing ACR in C57BL/6 recipients. The disruption of the IL-12 or IFN-γ genes in C57BL/6 mice shifted ACR to AVR, and resulted in concomitant recipient resistance to CsA therapy. Conversely, disruption of IL-4 gene in BALB/c mice markedly attenuated AVR and significantly prolonged allograft survival. These data suggest that the distinct cytokine profiles expressed by different mouse strains play an essential role in regulating the pattern of rejection and outcome of CsA/rapamycin therapy.

Free Bone Graft Attenuates Acute Rejection and in Combination with Cyclosporin A Leads to Indefinite Cardiac Allograft Survival

“…We previously reported that C3H mouse hearts transplanted into BALB/c mice developed typical features of AVR (37,41). To determine whether bone grafting can prevent AVR, we took advantage of this model to study the ability of bone grafting alone or in combination with CsA to inhibit the humoral immune response against the allograft.…”

“…At necropsy, heart tissue samples were fixed in 10% buffered formaldehyde, embedded in paraffin, and sectioned at 5 m for H&E staining (37). The microscopic sections were examined in a blinded fashion for severity of rejection by a pathologist (B.G.).…”

“…Circulating anti-C3H donor or anti-third party C57BL/6 IgG and IgM Ab responses were evaluated in recipient sera by flow cytometry (Becton Dickinson) following appropriate incubation with either donor strain or third party strain splenocytes (37). Briefly, recipient mouse sera were obtained at the indicated time points from the various treatment groups, diluted 1/25 in PBS (determined by prior titration to be the most appropriate dilution for Ag-Ab recognition while avoiding Ag-Ab saturation), and incubated with C3H or C57BL/6 mouse splenocytes at 37°C for 30 min (40).…”

“…To simulate AVR in an animal model we used the C3H-to-BALB/c heterotopic cardiac allograft model, which resembles clinical AVR, in presentation and resistance to immunosuppressive therapy (37). We demonstrated that free bone grafting, together with a conventional immunosuppressant (e.g., cyclosporin A (CsA)), and without recipient preconditioning, was capable of inducing indefinite cardiac allograft survival with normal organ histology.…”

Distinct Subsets of Dendritic Cells Regulate the Pattern of Acute Xenograft Rejection and Susceptibility to Cyclosporine Therapy

“…Unlike allografts, Th1 cytokines such as IFN-␥ and IL-12 are beneficial to xenograft survival because of their negative effect on AVR. In recent findings, we demonstrated that distinct cytokine profiles expressed by different mouse strains played an essential role in regulating the pattern of rejection and outcome of cyclosporin A (CsA)/rapamycin therapy in allotransplantation (2). These data suggest that the cytokine profile appears to be a key factor in determining the pattern of rejection and susceptibility to immunosuppressive agents.…”