Biomedical subjects

U Heemann

Publications and source records attributed to U Heemann.

87 records · Page 5Linked to original sources

PubMed1994

Reversibility of chronic renal allograft rejection. Critical effect of time after transplantation suggests both host immune dependent and independent phases of progressive injury.

The characteristic and progressive morphological changes of glomerulosclerosis, interstitial fibrosis, and vascular obliteration that occur in renal allografts experiencing chronic rejection correlate directly with declining function and eventual graft loss. Using an established rat transplant model of chronic rejection where such changes occur in predictable sequence, allografts were retransplanted back into the donor strain at serial intervals after the initial engraftment to determine at what stage of development the lesions could still be reversed by removing the continuing immunological drive of the host. Morphological changes were compared with those in retransplanted isografts and nonretransplanted allografts at comparable time intervals. Histological and immunohistological characteristics of chronic rejection were reversible by retransplantation at or later than week 12 could not reverse the intense humoral and cellular immune responses, or the structural changes (particularly fibrosis) that developed after that period. However, the sparse but inevitably progressing cellular infiltration and cytokine expression in retransplanted and nonretransplanted isograft controls suggest the persistent influence of alloantigen-independent factors in addition to those of host immunity. Thus, the early stages of chronic rejection are alloantigen dependent and reversible, whereas the later changes were irreversible and alloantigen-independent factors appeared increasingly important.

Animals↗

PubMed1994

Successful heterotopic heart transplantation in rat.

Heterotopic heart transplantation in rats has become a substantial tool for numerous investigations. This report describes a surgical technique of infrarenal heterotopic heart transplantation with a prodigious surgical success rate which was developed over many years of practice. Difficulties arising from anatomic variations are depicted and alternative approaches are discussed.

Abdomen↗

PubMed1994

Long-term kidney isografts develop functional and morphologic changes that mimic those of chronic allograft rejection.

OBJECTIVE: This study examined antigen-independent factors in the pathogenesis of chronic rejection of organ transplants. SUMMARY BACKGROUND DATA: In addition to alloantigen-dependent events, antigen-independent factors can influence chronic rejection of organ allografts. Initial injury, including early ischemia and acute rejection, may contribute. METHODS: Kidney isografts were transplanted orthotopically into bilaterally nephrectomized rat recipients and studied functionally, morphologically and immunohistologically, at serial intervals up to 72 weeks after transplantation. Controls included chronically rejecting kidney allografts using a well-established model, non-nephrectomized and uninephrectomized animals with a native kidney that had undergone initial ischemia and uninephrectomized rats whose remaining kidney had been manipulated operatively. RESULTS: Allograft recipients developed progressive proteinuria after 12 weeks, with gradual renal failure ultimately leading to death. At the same time, morphologic changes, including progressive arteriosclerosis and glomerulosclerosis, tubular atrophy, and interstitial fibrosis, developed. Immunohistologically, macrophages infiltrated glomeruli during this period and cytokines became upregulated. Comparable changes occurred in isografts, but later, beginning after week 24 and progressing thereafter. The single ischemic kidney in uninephrectomized controls also developed the same lesions; no comparable changes were noted in other control kidneys. CONCLUSIONS: Antigen-independent functional and morphologic changes occur in long-term kidney isografts that resemble those appearing considerably earlier in allografts that reject chronically. Initial injury and extent of functioning renal mass may be important factors for such late changes.

Animals↗

PubMed1994

Host leukocytes and their products in chronic kidney allograft rejection in rats.

Bilaterally nephrectomized Lewis recipients of Fisher 344 (F344) kidney allografts, treated with CyA (1.5 mg/kg/day x 10), develop progressive changes of chronic rejection. Treated F344-to-F344 acted as isograft controls. Proteinuria was determined sequentially. Grafts were harvested 8, 12 and 16 weeks after transplantation (n = 9/group/time period). Infiltrating host cells and their products were assessed in chronically rejecting grafts by histology and immunostaining using mAbs for monocyte/macrophages, T-cells, ICAM-1, LFA-1 and cytokines. For in vitro binding studies, snap-frozen sections of transplanted kidneys were incubated with monocytes/macrophages and lymphocytes isolated from peripheral blood (PBL) of naive animals. For in vivo migration studies, naive cell populations were labeled with Bis-Benzamide and transferred i.v. to grafted animals at weeks 8, 12 and 16 (n = 3/group); grafts were harvested 24 h later and cell localization assessed under immunofluorescence. Increasing numbers of ED1 + monocytes/macrophages in allografted kidneys peaked at 16 weeks, localizing preferentially in glomeruli, where IL-1, IL-6 and TNF-alpha expression had also become intense and correlated with progressive glomerulosclerosis. Binding studies corroborated these results. In vitro, a few monocytes/macrophages bound to glomeruli and vessels at 8 weeks; by 12 weeks, binding to glomeruli was high (72% of cells). In vivo, large numbers of transferred labelled monocytes/macrophages were found in kidney allografts at 12 weeks (23%, isografts; < 7%, P < 0.01). In contrast T cells (primarily CD4+) were a consistent feature in allografts elevated as compared to isografts and correlating with in vitro and in vivo binding patterns; associated cytokines included IL-2, IFN- and TNF-alpha. Functional data followed these results: urine protein excretion by allograft recipients increased from baseline at 8 weeks (12 mg/day) to > 50 mg/day at 16 weeks at which point animals were beginning to die of renal failure; proteinuria in isografted rats did not increase during this time period. These results suggest that monocyte/macrophage and CD4+ T cells and their products are important in chronic kidney allograft rejection, contributing to the progressive sclerosis and fibrosis.

Animals↗

PubMed1994