Gary R. Cain

Effects of combination cyclosporine/mizoribine immunosuppression on canine renal allograft recipients

Heterotopic renal allografts following bilateral nephrectomies were placed in 21 healthy mongrel dogs. One group of 11 dogs received cyclosporine (5 mg/kg/ 24 hr, orally), and 1 group of 10 dogs received cyclosporine and mizoribine (5 mg/kg and 3 mg/kg/24 hr, orally). Body weights, blood cell counts, serum chemistry profiles, serum electrolyte levels, urinalysis with cytology and culture, lymphocyte stimulation assays, immunoglobulin levels, whole blood levels of cyclosporine, and serum levels of mizoribine were followed. At the end of each survival period, necropsy and histopathologic examinations were performed. The mean survival time for the cyclosporine group was 12.8 ± 7 days. The mean survival time for the cyclo-sporine/mizoribine group was 33.6 ± 16.4 days, significantly longer (P=.0006) than the cyclosporine group. Death in the cyclosporine/mizoribine group was attributed to the combined effects of renal allograft rejection and development of a mizoribine-dependent enteritis. Serum levels of mizoribine were greater in the last half of the survival period due to compromised renal excretion of the drug. There were no complications due to infection, myelosuppression, or hepatotoxicity. Combination cyclosporine/mizoribine immunosuppression enhanced canine renal allograft survival in this study. Monitoring serum concentrations of mizoribine is imperative to determine toxic (enteritis) levels. Availability of an intravenous form of mizoribine would facilitate immunoregulation during periods of variable intestinal absorption or renal excretion.

Myasthenia gravis and polymyositis in a dog following fetal hematopoietic cell transplantation.

Myasthenia gravis and focal polymyositis occurred in a dog following successful transplantation of DLA-identical fetal liver hematopoietic cells. There was no evidence of acute or chronic graft-versus-host disease. Antibodies to acetylcholinesterase receptor and immune complexes reactive with myoneural junctions were demonstrated, as well as focal inflammation with perifascicular and type 2 muscle atrophy. The dog responded to treatment with prednisolone and pyridostigmine.

Mizoribine serum levels associated with enterotoxicity in the dog.

To prevent or minimize mizoribine enterotoxicity in organ transplant recipients and to differentiate mizoribine enterotoxicity from other causes of enteritis, serum levels of mizoribine that produced subclinical and clinical signs of enterotoxicity were determined in the dog. When mizoribine was administered orally at 12-hr intervals, half the dogs studied showed clinical evidence of gastrointestinal disturbances (vomiting, diarrhea, and anorexia) without histopathologic signs of enterotoxicity. Using a 24-hr oral-dose schedule, clinical signs of gastrointestinal disturbances and histopathologic evidence (mucosal degeneration, crypt degeneration, and necrosis) of enterotoxicity were encountered when the mean 12-hr mizoribine serum level was 0.97 +/- 0.4 microgram/ml or greater. Histopathologic signs of enterotoxicity with repeated positive fecal occult blood assays and without clinical signs of gastrointestinal disturbances occurred when the mean 12-hr serum level was 0.53 +/- 0.17 microgram/ml or greater. Oral administration of cyclosporine did not exacerbate mizoribine enterotoxicity in the dog when administered with mizoribine at a dose that produced histopathologic signs of enterotoxicity.

Effects of administration of recombinant human interleukin-2 in dogs

The clinical and immunohaeamatological effects of recombinant humen interleukin-2 (rhIL-2) administration were evaluated in normal dogs. Three groups of three dogs per group were administered rhIL-2 subcutaneously at a dose of 6 × 104 IU, 6 × 105 IU, or 6 × 106 IU/kg once daily for five consecutive days. Toxic clinical signs were limited primarily to diarrhoea, the severity of which, was dose dependent, with resolution within 7 days of the last rhIL-2 injection. Marked circulating eosinophilia occurred in dogs of the two highest dose groups and transient rise in blood lymphocyte numbers occurred in dogs given the highest dose of rhIL-2. The most significant immunological effects were elevated in vitro conA and pokeweed mitogen-stimulated lymphocyte blastogenic responsiveness in the highest dose group and dose-dependent elevation of antigen-specific antibody (IgG and IgM) production. Peak relative antibody production was markedly elevated, as compared to controls, in dogs administered 6 × 105 IU, 6 × 106 IU rhIL-2/kg.

Establishment and partial characterization of a radiation-induced canine monocytic leukemic cell line (RK9ML-1)

A myeloid leukemic cell line, designated RK9ML-1, was established from a dog with acute radiation-induced monocytic leukemia. Based on cytochemical stains which reacted positively only with nonspecific esterase, morphological and ultrastructural characteristics which indicated the presence of phagocytic vacuoles and lysosomal bodies, and cell surface properties which indicated the presence of Fc receptors, all the findings support that RK9ML-1 is of monocytic lineage. Chromosomal analysis of the cell line indicated the cells to be hypodiploid with acrocentric autosomes characteristic of canine cells.

Transplantation of DLA-compatible and incompatible fetal liver hematopoietic cells in dogs.

Requirements for sustained engraftment of fetal liver hematopoietic stem cells were evaluated in 45 dogs. Pretransplant preparative treatment with total-body irradiation, 14.7 Gy, permitted engraftment of DLA-compatible fetal liver cells. Radiation alone was inadequate in DLA-haploidentical or DLA-mismatched transplants; none of 5 dogs had engraftment. Addition of cyclosporine facilitated engraftment. The combination of 14.7 or 16.1 Gy total-body irradiation (TBI) and cyclosporine allowed engraftment in 15 of 19 (78%) dogs receiving DLA-histoincompatible grafts and 11 Gy TBI plus cyclosporine allowed engraftment in 4 of 10 dogs. Restoration of granulopoiesis and thrombopoiesis was rapid; recovery of lymphocytes was relatively delayed, especially in recipients of incompatible fetal liver cells. Cumulative one-year survival was decreased in recipients of incompatible grafts due to early posttransplant infections. These data suggest that fetal liver transplantation is a potential approach in patients who lack an HLA-identical donor for bone marrow transplantation.