Immunobiology and long-term graft function in a transplant heterotopic renal rat model.
BACKGROUND
The Th1-Th2 paradigm proposes clonal expansion of Th2 lymphocytes as the basis of allograft tolerance. The Th2 cells have been found to be present in recipients with long-term allograft survival. However, the presence of Th2 cells and tolerance is not a uniform finding. Previously we have shown that pre-engraftment single dose rapamycin and a 7-d course of cyclosporin induce transplantation tolerance to 120 d. In the present study, we investigated the immunobiology of grafts in a long-term follow-up (>350 d).


METHODS
Kidney allografts (n = 7), isografts (n = 5) and single nephrectomy (n = 3) groups were followed for 350 +/- 87 d. Heterotopic kidney transplant was performed by the same surgeon in the allograft group (ACI-Lewis) and the isograft group (Lewis-Lewis). The left kidney was removed in the single nephrectomy group. The allograft group was treated with pre-engraftment single dose rapamycin and a 7-d course of cyclosporin. A kidney biopsy was performed at midpoint time for histological study and tissue was frozen for measuring intragraft cytokine expression (IL-4, IL-10) in all animals. Prior to biopsy, serum blood urea nitrogen (BUN) and creatinine (Cr) levels were studied. Serum BUN, Cr levels, plus 24-h urinary protein (PRO) were measured prior to sacrifice. Randomly, four allograft rats received skin grafts (ACI, Lewis and Buffalo skin donors) after kidney biopsy. Skin grafts were studied for a mean of 6 weeks for signs of acceptance or rejection. Analysis of variance (ANOVA) with Tukey's test was used; p < 0.05 was considered statistically significant.


RESULTS
The mean follow up was 352 +/- 87 d. BUN and Cr levels at biopsy time (mean 214 d) were not statistically different between the three groups (p = 0.19 and p = 0.66). At sacrifice (mean 352 d), BUN, Cr and PRO were statistically different between allograft and isograft groups (p = 0.013), and between allograft and single nephrectomy groups (p = 0.027). Functional and histological signs of graft loss occurred in three of seven (42.8%) of the allografts at 352 d. Using BANFF criteria, three allografts at biopsy time and seven allografts (100%) and four isografts (80%) at sacrifice time developed chronic histologic changes. Intragraft overexpression of IL-4 and IL-10 was seen at biopsy and sacrifice time in six of seven allografts and one of five isografts. All donor specific skin grafts (ACI-Lewis) on allografts were accepted and third party (Buffalo) donor skin grafts were rejected in all animals (>95% skin necrosis).


CONCLUSIONS
This highly stringent, functional, renal transplant model yields 100% normal renal function as compared with isografts at 120 d follow-up. With the follow-up extended to 350 d, 43% of the allografts loose function and develop a chronic allograft histology despite a demonstrated intragraft Th2 cytokine dominance and donor specific skin graft acceptance.
Maluf
D G
DG
Medical College of Virginia, Virginia Commonwealth University, Division of Transplant Surgery, and Department of Pathology, Richmond, VA 23298-0254, USA.
Fisher
R A
RA
Riley
R
R
Wallace
M
M
Tawes
J
J
Bu
D
D
Posner
M
M
D000818:Animals; D016207:Cytokines / Q000378:metabolism; D006084:Graft Rejection / Q000276:immunology; D016753:Interleukin-10 / Q000378:metabolism; D015847:Interleukin-4 / Q000378:metabolism; D007668:Kidney / Q000473:pathology; D016030:Kidney Transplantation / Q000276:immunology / Q000502:physiology*; D008297:Male; D023421:Models, Animal; D051381:Rats; D011912:Rats, Inbred ACI; D011917:Rats, Inbred Lew; D013601:T-Lymphocytes / Q000276:immunology; D023001:Transplantation Tolerance / Q000276:immunology*; D016042:Transplantation, Heterotopic / Q000276:immunology / Q000502:physiology*; D014184:Transplantation, Homologous; D014185:Transplantation, Isogeneic
D016207:Cytokines; D016753:Interleukin-10; D015847:Interleukin-4