Renal homotransplantation in rats. I. Allogeneic recipients

Methods in renal research: kidney transplantation in the rat

Kidney transplantation in small animals has been crucial in the development of anti-rejection therapies. While there is no substitute for a skilled microsurgeon, there are many aspects of the transplant procedure that can be modified to optimize the reproducibility and utility of the technique. This article provides a detailed description, including video recording, of orthotopic kidney transplantation in the rat. The key variables in the technique are also discussed.

Kidney transplantation in rats: an appraisal of surgical techniques and outcome

Renal transplantation in rats is an essential experimental tool in transplantation research. The surgical procedure per se could affect the outcome of an experiment, independent of the hypothesis addressed, therefore requiring a standardized method which should be comparable across studies. To date, however, there is little information on the optimal surgical technique. We performed a Medline search on original articles published between 1965-2001 in order to evaluate whether specific technical issues affecting the outcome of the procedure could be defined. Articles that reported on a novel microsurgical procedure, or whose main purpose was the outcome of a surgical technique itself, were included in the analysis. From 2,060 retrieved publications, 34 corresponded to the selection criteria (rats and microsurgery and technique and kidney or renal transplantation). Among the essential determining factors for a good outcome, body weight >200 g and warm ischemic time <30 min were identified. Other important factors were the techniques used for vascular (end-to-end and end-to-side procedure or sleeve technique) and ureteral (bladder patch or end-to-end procedure) anastomosis. Gender, animal strain, type of anesthesia, prophylactic administration of antibiotics, and type of flushing solution did not affect the success of renal allografts. In order to avoid a bias related to the surgical procedure in rat renal transplantation, a warm ischemia time <30 min in animals with a body weight >200 g seems to be essential. Also, end-to-end or end-to-side vascular anastomoses are preferable to the sleeve technique. Other factors do not influence the immediate function of the graft.

Kinetics of intragraft cytokine expression, cellular infiltration, and cell death in rejection of renal allografts compared with acceptance of liver allografts in a rat model: early activation and apoptosis is associated with liver graft acceptance

BACKGROUND

Liver transplants in the rat strain combination PVG-to-Dark Agouti are spontaneously tolerated, whereas kidney transplants in the same strain combination are rejected in 7-9 days.

METHODS

To identify organ-specific differences that might yield further information about the mechanism of tolerance induction in this strain combination, liver or kidney grafts, spleen, and draining lymph nodes were harvested at days 1, 3, 5, and 7, and examined by immunohistochemistry, terminal deoxynucleotide transferase-mediated dUTP nick end labeling assay, and reverse transcriptase-polymerase chain reaction for interferon-gamma, interleukin (IL)-2, IL-4, and IL-10.

RESULTS

Renal allograft rejection was associated with the progressive development of an intense mononuclear cell infiltrate. Markers of lymphocyte activation and cytokine up-regulation appeared from day 3, and many apoptotic parenchymal cells were noted on days 5-7, at the peak of rejection. Conversely, liver allograft tolerance was associated with more rapid infiltration by activated T cells and earlier increases in cytokine expression, but with a more limited degree of cellular infiltration. Concurrent with the early activation, high levels of apoptosis were found in areas of leukocyte infiltrate, paralleling the disappearance of activated T cells from the graft between days 3 and 5.

CONCLUSIONS

Apoptosis of infiltrating leukocytes in liver allografts may represent an important process in the induction of spontaneous liver transplant tolerance and may underlie the abortive nature of the effector response observed within tolerated livers. In contrast, activated cells in renal allografts in the same strain combination survive and proliferate, express high levels of cytokines, and are efficient in bringing about graft destruction.

New rapid technique for renal transplantation in the rat

Present techniques for renal transplantation in the rat include a period of 20-25 minutes warm ischemia. Our method combines a recently described sleeve anastomotic technique for the renal artery, conventional end-to-end anastomosis of the renal vein, and implantation of the ureter into the bladder. This has resulted in a reproducible ischemic interval of 12-14 minutes. Plasma creatinine and histological features in animals sacrificed from 10 to 30 days after transplantation were within normal limits with no evidence of ischemic damage. A further advantage of the technique is that kidneys can be exchanged between the donor and recipient. It is recommended that this procedure, which reduces the ischemic interval by up to 50%, should be learned and employed in studies of renal transplantation in the rat, especially if such studies include the prior administration of cyclosporine, which may aggravate the effects of ischemia.

Cellular basis of allograft rejection

In summary, we currently hypothesize that systemic immunization within the lymphoid tissue is amplified by a sequence of specific and non-specific immunological interactions which lead to enrichment of specifically sensitized T-cells at the graft site. Nascent sensitized cells enter the graft via non-specific attractants generated by the healing response. The interaction of alloantigen with responder T-cells bearing specific alloantigen receptor results in production of lymphokines which increase blood flow and vascular permeability, and which are chemotactic for circulating lymphocytes. These events and other non-specific events recruit circulating cells regardless of the specificity of their sensitization. The state of activation of these cells may control their presence within the circulation. Cells which are more activated are released more readily from the lymphoid depots into the circulation so that relatively more specifically sensitized (though not necessarily mature cytotoxic cells) cells would enter the circulation and be recruited to the graft. At the allograft, there is an escalating sequence of lymphokine production and non-specific recruitment. II-1 has been demonstrated to be capable of mediating such recruitment. A second phase of amplication occurs at the graft site where precytotoxic (x-ray-sensitive) cells mature and expand into cytotoxic (x-ray-resistant) cells. These cells may be important effector cells of allograft rejection in concert with many unsensitized cells which can participate in non-specific attacks on graft viability. The essential point made from the studies summarized here is the consideration that trafficking patterns of lymphocytes and recruitment of lymphocytes and other inflammatory cells are in essential component to the local mechanism of graft rejection. The relative importance of specificity of response has not been defined.

Prolongation of canine allograft survival with donor pretreatment

Donor pretreatment of 100 mg/kg each of cyclophosphamide (CY) and methylprednisolone (P) infused 5 hours before nephrectomy invariably prolongs the survival of DLA mismatched, MLC incompatible nonlittermate Beagle renal allografts as well as the survival of mongrel renal allografts. The effect of donor pretreatment appears to be mediated by cyclophosphamide and its metabolites because methylprednisolone pretreatment does not significantly prolong survival. Methylprednisolone is needed, however, because it abolishes cyclophosphamide pretreatment mediated early but transient postoperative renal (allograft) insufficiency. The effect of donor pretreatment appears to be mediated by drugs residing in the graft; mannitol infusions given 1 hour prior to donor nephrectomy or peroperatively into the recipient decrease the renal cortical content of carbon 14 cyclophosphamide and its metabolites and abolishes the prolonged survival. Because donor pretreated kidneys contain less than 0.5% of the infused dose of carbon 14 cyclophosphamide, the drugs appear to exert their effect locally in the transplanted kidney. Donor pretreatment mediating prolonged canine renal allograft survival appears to be an example of influencing a biological process by a localized drug delivery by virtue of unique properties of the drug and because early postoperatively host sensitization occurs mainly at the site of the graft.

The pathogenesis of renal allograft rejection: an experimental investigation in sheep

Fifteen renal allografts and 5 autografts were placed into the necks of bilaterally nephrectomized sheep. Ten of the sheep with allografts were also treated with azathioprine (5 mg/kg) and prednisone(1.5 mg/kg) daily. There were no changes in the distribution of immunoglobulins or of beta lC globulin which could be associated with the rapid decline in glomerular filtration rate observed in untreated allografts after 2 d and in immunosuppressed allografts after 6 d. However, this functional decline was associated with the development of interstitial oedema, lymphocyte infiltration, swelling of tubular and glomerular cells, and necrosis of the outer two-thirds of the renal cortex. Thus the onset of progressive cortical ischaemia appears to be an important event leading to renal allograft failure in sheep.

Association of interstitial nephritis with tubule cell injury and proliferation in NZB/NZW mice

The relationship between renal interstitial mononuclear cell infiltration and renal tubule cell (TC) proliferation has been examined in (NZB X NZW) F1 hybrid (B/W) and control mice. TC proliferation was measured by tritiated thymidine ([3H]TdR) injection, autoradiographic examination of kidney sections and enumeration of labelled tubule cells. In B/W mice interstitial infiltration began at 5 months and reached a peak at 9 months. Proliferation of TC began at 7 months and also reached a peak at 9 months. Control mice consisting of NZB, CBA/J and C57Bl/6J mice showed no increase with age. When the percentages of labelled TC in areas adjacent to interstitial infiltrates and distant from them were compared, the TC adjacent to infiltrates showed an approximately four-fold greater amount of labelling. Ultrathin light and electron microscopic sections demonstrated TC injury in areas in close proximity to infiltrates. These studies suggest that mononuclear cells in the interstitial infiltrate may be injurious to TC, leading to a sequence of injury and subsequent regeneration of these cells. In diseases in which interstitial nephritis is present, such as Sjögren's syndrome, the interstitial infiltrate may contribute to the observed TC dysfunction.

Lymphocyte-epithelium interaction during rejection of nonisogeneic rat tracheal grafts

Rat tracheal tissues were maintained in organ culture for 1 to 2 weeks and then implanted heterotopically into syngeneic and outbred hosts. The grafts and surrounding tissues were removed at regular intervals and examined by light and electron microscopy. Allogeneic grafts were consistently rejected, and a constant pattern of immunologic response was observed during rejection. Infiltration by mononuclear cells occurred initially in the subepithelial region. Subsequently, small lymphocytes migrated through the basal lamina and insinuated themselves between the differentiated epithelial cells. Larger cells resembling activated lymphocytes were also present in the intraepithelial infiltrate. Both type of lymphocytes had cellular processes in contact with epithelial cells, but there was no associated death of epithelial cells. Later, the infiltrate in some areas of the epithelium inclded dividing cells and other large cells exhibiting ultrastructural features suggesting blast transformation. Epithelial cell death was evident during this phase. The sequence of events may reflect a process of recognition and specific cytotoxic action by lymphocytes.

Vascular transplant rejection of rat renal allografts across strong histocompatibility barriers

Sixty-one rat renal allografts were studied by light microscopy and in 18 cases also by immunohistology. Donor and recipient differ at a major histocompatibility locus in the one group (n = 37), and by an additional weak histocompatibility antigen in the other (n = 24). The mean survival time is 10.4 days and 8.3 days, respectively. A semiquantitative grading of the histologic findings shows that in both groups the rejection is predominantly manifested by lesions of extraglomerular and glomerular vessels, whereas mononuclear cell infiltration appears to be of less significance. The essential findings are necrosis of arteries and arterioles, necrosis of glomerular cells with mesangiolysis, and focal tubular necroses. This morphologic rejection type is interpreted as the result of a mixed humoral and cellular immune response, although the constant participation of circulating antibodies in the vascular damage could not be established. Since the tubular necroses correlate well with the degree of vascular alterations, but not with the mononuclear cell infiltration it would seem reasonable to conclude that these necroses are secondary to ischemia produced by vascular lesions. Finally, there is no significant difference in the degree of rejection between the two donor/recipient groups, and, therefore, there is no morphologic evidence for an increase of the rejection process by additional weak histoincompatibility in the examined strain combinations.

Morphological changes in indefinitely surviving enhanced ectopic rat cardiac allografts

The histological changes of ectopic cardiac allografts in rats have been studied. These consisted of (a) a diffuse chronic inflammatory cell infiltrate of the myocardial interstitium accompanied by variable degrees of fibrosis (b) variable degrees of intimal hyperplasia of the coronary arteries with segmental disruption of the internal elastic lamina.

Ultrastructure of cells infiltrating human kidney allografts

Cell infiltration is commonly observed in human renal allograft biopsies. This infiltration was investigated using electron microscopy for a more precise assessment of the nature of these cells. More than 3000 cells infiltrating twenty-five renal allograft biopsies were studied. Six cellular types were distinguished and a mean percentage of each type was calculated. Only one-half of these cells were normal or transformed lymphocytes (including small lymphocytes: 22-3 +/- 3-8%, 'intermediary' cells: 22 +/- 3-6%, blast-like cells similar to MLC transformed lymphocytes: 8-1 +/- 2-4%. A relatively high number of plasmocytes (12-4 +/- 2-5%) and a still higher percentage of macrophages (28-5 +/- 4-6%) were found. Granulocytes represented only 2 +/- 0-8%of the cell population. Variations of the mean percentage of these cellular types were studied in various clinical situations.

Renal tubular acidosis in chronic liver disease

Renal tubular acidosis of the gradient or classic type, thought to be due to a disorder of the distal tubule, has been found to occur in 32% of 117 patients with chronic liver disease. Whilst the cause of this disorder is probably multifactorial, immunological mechanisms are considered to play a major role. The presence of this disorder might well be a cause, rather than the result of, the various electrolyte abnormalities seen in patients with chronic liver disease.

Immunologic enhancement of rat renal allografts. II. Immunohistology of acutely rejecting and passively enhanced grafts

Unmodified renal transplants from (Lewis x Brown Norway) F(1) hybrids to Lewis rats show deposition of immunoglobulin (IgG) and complement in the arteries, which cause an acute necrotizing arteritis with ischemic necrosis of the grafts. Treatment with a single dose of enhancing antiserum at the time of transplantation prevents the arterial deposition of IgG and complement, and the vascular lesions. The enhancing antibody probably acts peripherally by blocking crucial antigenic sites in the graft vasculature, since cytotoxic alloantibody is detectable in the circulation of both control and enhanced recipients. Unmodified allografts also show deposition of IgG in glomeruli accompanied by glomerular necrosis. Immunofluorescent studies indicate that these glomerular lesions are mediated by complexes of antigen and alloantibody, and at least partially also by a nonhistocompatibility antibody directed against antigens in glomerular endothelial cells. Enhancing antiserum treatment reduces glomerular IgG deposition and thus greatly mitigates the glomerular lesion as well.

Immunologic enhancement of rat renal allografts. I. Comparative morphology of acutely rejecting and passively enhanced grafts

The acute unmodified rejection of (Lewis x Brown Norway) F(1) to Lewis renal allografts is characterized by an early and progressive lymphoid cell infiltrate, glomerular necrosis, necrotizing arteritis and ischemic cortical necrosis leading to graft destruction. A single low dose of enhancing antiserum given at the time of transplantation prolongs graft survival by abrogating the necrotizing lesions in glomeruli and arteries and the subsequent cortical necrosis. Passive enhancement in this model is interpreted as representing predominantly a block in the humoral antibody-mediated rejection response. It is suggested that the block is effected mainly, peripherally, ie, at the level of the transplanted kidney itself.

Thymus-dependent lymphocytes in tissue sections of rejecting rat renal allografts

Lewis kidneys were grafted into BN recipients and examined at daily intervals up to 6 days after grafting with immunofluorescent reagents. A horse antiserum specific for T lymphocytes revealed an increasing number of T lymphocytes in the cellular infiltrates of rejecting allografts. These were detectable 1 day after grafting, reached a maximum 3 days later, and were relatively diminished at 6 days. In control isografts and nonimmunological inflammations of kidney, a small number of dispersed T lymphocytes was seen. A rabbit antirat thymocyte antiserum, given to allografted BN rats, prolonged survival of the grafts and decreased the cellular infiltrate and the number of T lymphocytes in the infiltrates. We conclude that in graft rejection there is a flow of T lymphocytes into areas of tissue damage and these T lymphocytes are immunologically reactive to graft antigens.

Peroxidase arthritis. II. Lymphoid cell-endothelial interactions during a developing immunologic inflammatory response

The interaction of lymphoid cells with vascular endothelium was studied during the development of immunologic synovitis in response to repeated intraarticular injections of a heterologous protein antigen. Lymphoid cells emigrated in venules and small veins, both by penetrating the endothelial cytoplasm and by traversing intercellular junctions. Frequent endothelial mitoses were coincident with lymphoid cell emigration. Endothelial cells in the involved vessels increased in number and bulged prominently into the vascular lumen. Endothelial nuclei contained dispersed chromatin and prominent nucleoli; the cytoplasm contained many vacuoles and abundant polyribosomes and rough-surfaced endoplasmic reticulum. Intercellular junctions were numerous and complex. These phenomena were prominent in rabbits studied after 12 to 16 daily injections; they then receded, despite continued antigenic stimulation. In animals studied after 35 or 37 daily injections, the venules appeared relatively normal, and lymphoid cell emigration was observed infrequently. Growth of new vessels was prominent at this stage. The present data do not establish whether the endothelial changes were the cause or the result of lymphoid cell emigration, although the latter seems more likely. Further studies are needed to elucidate the exact nature of these interactions.

The influence of cyclophosphamide on the rejection of allogenic rat kidney transplants. An in vitro study of cell-bound and antibody-mediated immunity

A ⁵¹Cr in vitro system was used to study the influence of cyclophosphamide on: (1) The capacity of rat lymphocytes to destroy allogeneic kidney cells. (2) The formation of enhancing and cytoaggressive antibodies. (3) The sensitivity of allogeneic rat kidney cells to an attack from lymphocytes and/or antibodies.

It was found that: (1) Lymphocytes from a non-immunosuppressed transplant-recipient rat had a clear ability to destroy the allogeneic kidney cells. (2) Serum from a non-immunosuppressed recipient rat without complement had a slight blocking or enhancing effect. (3) Antibodies capable of exerting a cytoaggressive action on allogeneic kidney cells together with complement were produced in non-immunosuppressed recipient rats. The amount of these antibodies diminished when cyclophosphamide was given. (4) Cyclophosphamide treatment diminished the number of white blood cells and the number of lymphoid cells in the thoracic duct. When the same number of thoracic duct cells as in the non-immunosuppressed group was used about the same cytoaggressive effect occurred. Thus cyclophosphamide had a `quantitative' but not a `qualitative' depressive effect on cell bound immunity. (5) Cyclophosphamide treatment had no effect on the enhancing activity in serum. No differences were found between transplanted and non-transplanted target kidney cells.

The role of the sixth component of complement in the rejection of kidney xenografts

The time of rejection of dog kidney grafts in normal and in C6-deficient rabbits was not significantly different. It is concluded that the last four components of complement are not involved in this form of violent xenograft rejection. The requirement for the first components may be explained by polymorphonuclear leucocyte chemotaxis, since these cells were found in the glomeruli of rejected kidneys.

Intrarenal complement fixation by cytotxic antibodies

The reactivity of histocompatibility antigens with serum antibodies and complement was studied in a short term model of allotransplantation. Lewis and DA rat kidneys were perfused with cytotoxic antisera and tissue sections analyzed for adsorption of fluorescent antibodies against gamma-globulin and complement (beta(1C) protein). Both, the presumed cytotoxic antibody and C were localized at similar sites in the endothelial lining and in the walls of the arterial vessels and of the larger veins. The pattern of immune globulin deposition was distinct from that observed in glomerulonephritis. It may thus become helpful in the differential diagnosis between graft rejection and glomerulonephritis. At the sites of the deposits, the endothelial cells appeared enlarged and their nuclei protruded into the lumen. The findings are in line with the hypothesis that an antibody-mediated local activation of serum complement may be involved in the destruction of allografted tissue.

Allografts in genetically defined rats: difference in survival between kidney and skin

Although skin allografts from inbred donors of the Fisher strain to inbred male Lewis recipients regularly show acute rejection within 12 days, orthotopic kidney allografts between untreated animals, in this same combination of strains, usually remain functionally intact for longer than 100 days. Since such renal allografts persist despite previous or concomitant rejection of skin allografts, neither acquired tolerance nor nonspecific immunosuppression can explain the surprisingly prolonged kidney survival. Many factors appear to be responsible for the disparate survival times observed. Tentatively, these factors are (i) antigenic differences between kidney and skin, (ii) intervention of immunological enhancement, and (iii) physiological differences in vulnerability between kidney and skin.

Pathogenesis of a local graft versus host reaction: immunogenicity of circulating host leukocytes

A local invasive-destructive reaction typical of that seen in allograft rejection occurs when Lewis rat spleen cells are inoculated under the capsule of Lewis kidney freshly grafted into F(1) hybrid hosts. Thus the donor lymphoid cells can be immunogenically stimulated by circulating host leukocytes and the interaction of these two cell populations results in nonspecific damage to kidney parenchyma. The results indicate that passenger leukocytes in organ allografts may be important immunogenic agents.

Heterotopic liver transplantation utilizing inbred rat strains. I. Characterization of allogeneic graft rejection and the effects of biliary obstruction and portal vein circulation on liver regeneration

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Renal homotransplantation in rats. II. Tolerant recipients

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The role of anti-glomerular basement membrane antibody in the pathogenesis of human glomerulonephritis

These observations established the presence of anti-GBM antibodies in the sera and/or kidneys of six humans with glomerulonephritis. Further, it seems clear that these antibodies do combine with the host's glomeruli in vivo and with GBM antigen of several species in vitro. Transfer of acute glomerulonephritis to normal recipient monkeys was possible with serum or renal eluate IGG from the three patients with anti-GBM antibodies in whom sufficient material was available. Based on this transfer of nephritis and on the presence of these antibodies at the site of injury in the nephritic kidneys of both the patients and the recipient monkeys, it seems likely that they are at least a contributing, if not primary, cause of the glomerular injury. The frequency of anti-GBM antibodies in human nephritis is not certain, but on the basis of preliminary observations it would appear that they are present in all cases of Goodpasture's nephritis and somewhat less than half of the cases of subacute and chronic glomerulonephritis of adults. The nature and source of immunogen stimulating the production of anti-GBM antibodies is not known, but the presence of potentially nephritogenic GBM antigens in normal urine raises the question of possible autoimmunization. From a practical point of view, it appears that patients forming anti-GBM antibodies may not be good candidates for renal transplantation since they are likely to produce in the transplants the nephritic changes already suffered by their own kidneys.