Predominant expression of T helper 2 cytokines and altered expression of T helper 1 cytokines in long-term allograft survival induced by intrathymic immune modulation with donor class I major histocompatibility complex peptides.
BACKGROUND
We have recently demonstrated that three synthetic peptides corresponding to the alpha-helices of the alpha1 and alpha2 domains of the donor class I RT1.Aa molecule served as efficient CD4+ T-cell epitopes for indirect recognition of this molecule during cardiac allograft rejection in the PVG.R8-toPVG.1U rat strain combination. These peptides induce long-term graft survival when injected into the thymus 7 days before transplantation under the cover of transient immunosuppression with anti-rat lymphocyte serum. In this study, we analyzed intragraft cytokine gene expression to test whether immune deviation to the T helper (Th) 2 response is associated with long-term allograft survival in this model.


METHODS
Intragraft cytokine gene expression was analyzed using a competitive reverse transcription polymerase chain reaction method we developed for this study. Cytokine gene expression was quantified in control allografts (n=5) with acute rejection and allografts from intrathymically manipulated recipients with acute rejection (n=5), delayed rejection (n=7), or no rejection (n=8).


RESULTS
Long-surviving allografts expressed high levels of interleukin (IL)-4, IL-10, transforming growth factor (TGF)-beta, interferon (IFN)-gamma, and undetectable levels of IL-2. Allografts that were rejected in a delayed fashion expressed mostly IL-2, IFN-gamma, and TGF-beta with low or undetectable levels of IL-4 and IL-10. Acutely rejected allografts from unmanipulated controls or peptide-manipulated recipients expressed high levels of IL-2, IFN-gamma, TGF-beta and undetectable levels of IL-4 or IL-10. All allografts also expressed T-cell receptor Cbeta gene, providing evidence for the presence of T-cell infiltrates in the grafts.


CONCLUSIONS
These observations demonstrate that acute graft rejection in this model is associated with the expression of Th1 cytokines, IL-2, and IFN-gamma, whereas long-term survival is associated with predominant expression of Th2 cytokines, IL-4, and IL-10. The expression of IFN-gamma in long-surviving allografts in the absence of IL-2 provides evidence for altered activation of the Th1 response in this intrathymic immune modulation model.
Shirwan
H
H
Institute for Cellular Therapeutics, Allegheny University of the Health Sciences, Philadelphia, Pennsylavania 19102, USA.
Barwari
L
L
Khan
N S
NS
D000818:Animals; D016207:Cytokines / Q000096:biosynthesis*; D006085:Graft Survival; D016027:Heart Transplantation / Q000276:immunology*; D015395:Histocompatibility Antigens Class I / Q000276:immunology*; D007371:Interferon-gamma / Q000096:biosynthesis / Q000235:genetics; D016753:Interleukin-10 / Q000096:biosynthesis / Q000235:genetics; D007376:Interleukin-2 / Q000096:biosynthesis / Q000235:genetics; D015847:Interleukin-4 / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D051381:Rats; D011917:Rats, Inbred Lew; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014184:Transplantation, Homologous
D016207:Cytokines; D015395:Histocompatibility Antigens Class I; D007376:Interleukin-2; D016753:Interleukin-10; D015847:Interleukin-4; D007371:Interferon-gamma