Theodore C. Graham

Marrow toxicity of fractionated vs. single dose total body irradiation is identical in a canine model

PURPOSEnWe explored in dogs the marrow toxicity of single dose total body irradiation delivered from two opposing 60Co sources at a rate of 10 cGy/min and compared results to those seen with total body irradiation administered in 100 cGy fractions with minimum interfraction intervals of 6 hr. Dogs were not given marrow transplants.nnnRESULTSnWe found that 200 cGy single dose total body irradiation was sublethal, with 12 of 13 dogs showing hematopoietic recovery and survival. Seven of 21 dogs given 300 cGy single dose total body irradiation survived compared to 6 of 10 dogs given 300 cGy fractionated total body irradiation (p = .18). One of 28 dogs given 400 cGy single dose total body irradiation survived compared to none of six given fractionated radiation (p > .20). With granulocyte colony stimulating factor administered from day 0-21 after 400 cGy total body irradiation, most dogs survived with hematological recovery. Because of the almost uniform success with granulocyte colony stimulating factor after 400 cGy single dose total body irradiation, a study of granulocyte colony stimulating factor after 400 cGy fractionated total body irradiation was deemed not to be informative and, thus, not carried out. Additional comparisons between single dose and fractionated total body irradiation were carried out with granulocyte colony stimulating factor administered after 500 and 600 cGy of total body irradiation. As with lower doses of total body irradiation, no significant survival differences were seen between the two modes of total body irradiation, and only 3 of 26 dogs studied survived with complete hematological recovery. Overall, therefore, survival among dogs given single dose total body irradiation was not different from that of dogs given fractionated total body irradiation (p = .67). Similarly, the slopes of the postirradiation declines of granulocyte and platelet counts and the rates of their recovery in surviving dogs given equal total doses of single versus fractionated total body irradiation were indistinguishable.nnnCONCLUSIONnWithin the limitations of the experimental design, we conclude that single-dose and fractionated total body irradiation have comparable marrow toxicity in dogs.

Prevention of transfusion-induced sensitization to minor histocompatibility antigens on DLA-identical canine marrow grafts by gamma irradiation of marrow donor blood

Dogs given total-body irradiation and marrow transplants from DLA-identical littermates exhibit prompt and sustained hematopoietic engraftment. However, animals given three preceding blood transfusions from the marrow donor before transplant become sensitized and reject the marrow graft. Rejection is due to exposure to polymorphic minor non-DLA histocompatibility antigens expressed on blood mononuclear cells. We sought to determine whether heat treatment would prevent blood from sensitizing recipients in this model since heating blood to 45°C for 45 min abrogates the ability of blood mononuclear cells to stimulate in mixed lymphocyte culture. Three of 4 evaluable dogs given heat-treated blood before transplant rejected their marrow grafts. To prevent possible reexpression/reacquisition of mononuclear cell functional activity in vivo after transfusion, subsequent dogs were given heated blood that was additionally exposed to 2000 cGy gamma irradiation. Eight of 10 evaluable dogs given blood treated in this fashion engrafted. Unexpectedly, 9 out of 10 evaluable dogs transfused with blood treated only with gamma irradiation also engrafted. These results demonstrate that treatment of blood with gamma irradiation alone or in combination with heat prevents transfusion-induced sensitization to minor histocompatibility antigens. Results from this canine model suggest that blood products be gamma irradiated before transfusion in patients who are transplant candidates in order to prevent sensitization to minor histocompatibility antigens and reduce the risk of marrow graft rejection.

Marrow grafts between DLA-identical and homozygous unrelated dogs: evidence for an additional locus involved in graft-versus-host disease.

Marrow transplants were carried out between unrelated donor-recipient pairs of dogs that were homozygous and identical for DLA-A, B, C, and D, i.e., mutually nonreactive in mixed leukocyte culture. Recipients were conditioned for transplantation by 1,200 R of total body irradiation and then treated with intermittent methotrexate for 102 days in order to prevent or delay graft-versus-host disease (GVHD). Of 13 dogs that received transplants, 4 are surviving with good grafts and no GVHD for more than 12 to 20 minutes. Nine died, 6 with GVHD between days 26 and 141, 1 with wasting on day 65, 1 with interstitial pneumonia on day 83, and 1 with graft rejection on day 23. In comparison, the survival of 17 DLA-identical littermates treated in the same manner was significantly better with 16 surviving without GVHD (P less than 0.01), while the survival of 54 DLA-nonidentical littermates was significantly worse with only two surviving without GVHD (P less than 0.025). These results are incompatible with the concept that solely the loci detected by mixed leukocyte culture and serotyping are responsible for GVHD. One or more additional loci appear to be involved. Knowledg e of this locus (loci) is important if marrow grafting between unrelated individuals is to be successful. However, results also indicate that an unrelated compatible marrow graft is more likely to succeed than a graft from an incompatible littermate.

Studies of the use of L-leucyl-L-leucine methyl ester in canine allogeneic marrow transplantation.

L-leucyl-L-leucine methyl ester (Leu-Leu-OMe) is a lysosomotropic agent that selectively kills cytotoxic T cells and their precursors, natural killer cells, and monocytes but not helper T cells or other cells of hematopoietic origin. In this study, the effects of treatment of bone marrow and peripheral blood buffy coat with Leu-Leu-OMe on the outcome of allogeneic marrow transplantation were studied in several canine models. Whereas incubation of autologous marrow with Leu-Leu-OMe had no adverse effects on subsequent engraftment, incubation of marrow from dog leukocyte antigen (DLA)-identical littermates resulted in a high rate of graft failure. Previous studies have demonstrated that the addition of peripheral blood buffy coat allows engraftment of unrelated DLA-nonidentical marrow, and in this study we found that incubation of buffy coat with Leu-Leu-OMe did not alter this graft promoting effect. In a final experiment it was demonstrated that incubation of both marrow and peripheral blood buffy coat did not prevent the development of graft-versus-host disease in recipients of marrow from DLA-haploidentical littermates. In considering the eventual application of Leu-Leu-OMe in the clinic, these results are less encouraging than those previously reported using murine models.

Characterization of Malignant Lymphoma in Dogs and Use as a Model for the Development of Treatment Strategies

Malignant lymphoma develops spontaneously in dogs with an annual incidence of 24 per 100,000 [1]. Since these dogs are frequently seen by veterinarians they can, with the cooperation of the veterinarian and owner, be referred for study providing a unique model of a spontaneously occurring lymphoma in an out-bred species. We and others have carried out a series of studies in which the disease has been characterized pathologically and immunologically and has been shown to resemble human lymphoma in many ways. We have used this model to develop methods designed to improve and broaden the application of marrow transplantation to the treatment of malignant lymphoma.

Lymphocyte/Marrow Co-Cultures as a Tool to Detect Transfusion-Induced Sensitization and Predict Marrow Graft Rejection in Dogs

Recent reports from several investigators make it reasonable to assume that lymphocytes, specifically T-cells, play a role in stimulating hemopoiesis (7,10,-11,13,26). In keeping with these observations, we have reported that peripheral blood lymphocytes (PBL) from normal dogs significantly increase the number of in vitro erythroid colonies (EC) grown from DLA-identical littermate marrow (22). The magnitude of stimulation observed depended upon the ratio of lymphocytes to EC precursors cultured, suggesting that lymphocytes might interact directly with erythroid colony-forming units in some capacity.