Ruby F. Meredith

Possibility of graft-vs-leukemia determinants independent of the major histocompatibility complex in allogeneic marrow transplantation.

The role of major histocompatibility (MHC) versus non-MHC determinants in the antileukemic effect exerted by engrafted normal marrow (graft-vs-leukemia, GvL) was studied in Rauscher leukemic SJL/J mice. The marrow donor strains included normal syngeneic SJL/ J (H-2a), allogeneic C57BL/10 and 129/J (H-2b), congenic B10.S (H-2a, but otherwise genetically identical to the C57BL/10), and also F1 hybrid mice of the SJL/J and B10.S or C57BL/10 strains. Prior to transplant the recipients were exposed to a dose of total body irradiation that was large, but lower than that required to eliminate all hematopoietic precursors, such that GvL activity of the donor marrow would be necessary to avoid leukemic relapse. Total relapse within 60 days was observed when the syngeneic SJL/J donors were used. Transplantation either of the H-2b C57BL/10 or the H-2a B10.3 marrow resulted in approximately 50% unrelapsed survival at 4 months. In contrast, only 26% unrelapsed survival was obtained with H-2b 129/J marrow. Marrow from (SJL/J x B10.S)F1 hybrids yielded a survival curve that was intermediate between those for the two parental strains; a similar but somewhat improved, pattern was seen with (SJL/J x C57BL/10)F1-hybrid donors. The results suggest that although MHC genetic differences between the donor and recipient may produce a GvL effect in marrow transplantation therapy, other non-MHC determinants may also be capable of exerting an independent GvL effect of at least equivalent strength.

Methyl methane sulfonate induced enhancement of Friend viral leukemogenesis.

Exposure to the chemical carcinogen, methyl methane sulfonate, enhanced leukemogenesis in mice given threshold doses of Friend leukemia virus, as shown by peripheral white blood cell counts, splenomegaly and survival.

Stimulation of immune response in hybrid mice following Rauscher virus infection.

Summary The effect of Rauscher leukemia virus injection on the splenic PFC response to SRBC was measured in a mouse strain sensitive to the virus (SJL/J), one resistant to the virus (C57B1/10), and their F1 hybrid (SJL/JxC57B1/10)F1. In contrast to previous findings of a suppressive effect of Friend virus on PFC response in another hybrid of different resistant and sensitive strains, a significant immunostimulation was seen. Immunostimulation was also seen in the resistant parent when the PFC response level was measured 12 days or later after RLV infection, while the PFC response of the sensitive parent was nearly completely suppressed. Evaluation of the effect of RLV on the splenic masses of the three strains indicated a mild transient splenomegaly in the hybrid; a pronounced splenomegaly in the sensitive parent; and no effect on the resistant strain. Comparison of the data suggests that the change in splenic PFC number in the hybrid following RLV infection occurs as a function partially independent of changes in the total splenic mass.

Contrasting immune response following Rauscher leukemia virus infection in virus-susceptible vs. virus-resistant mice

Abstract Humoral (plaque-forming) and cellular (mitogenic) responses were monitored as a function of time after infection with a threshold lethal dose of Rauscher virus in virus-susceptible SJL/J mice and virus-resistant C57B1/mice. Plaque forming response was suppressed in the SJL/J, whereas in the C57B1/10, it was slightly elevated during the 2nd and 3rd weeks after infection; this correlated with a mild viremia. Increasing the dose of virus 40X did not significantly alter the humoral response pattern of either strain and did not cause the C57B1/10 response to mimic that of the SJL/J. For both strains the cellular immune response pattern differed from the humoral. Depression of T-cell mitogen responses occurred in the SJL/J, but at a later time than humoral response suppression. Neither T- nor B-cell mitogen responses were affected in the C57B1/10. The effect on mitogen responsiveness appeared to be independent of that on plaque-formation in both strains.

Fatal response suggestive of graft-versus-host reaction following transplantation of spleen cells from allogeneic athymic (nude) donors.

SUMMARY Normal female SJL/J mice were exposed to 950 R of total body irradiation (TBI) and transplanted with allogeneic spleen or marrow cells from normal or nude (athymic) C57BL/10 donors. With nude mouse donor marrow, no evidence of graft -versus-host (GVH) response was seen and all SJL/J recipients survived for more than 75 days. In contrast, when spleen cells taken from the same nude C57BL/10 donors were engrafted into SJL/J mice the incidence of fatalities among the recipients was 70% by 60 days. Furthermore, all of the recipients of nude mouse spleen cells showed signs strongly suggestive of GVH response. Comparative fatalities among the recipients of cells from normal donors were 27% for marrow at 60 days and 100% for spleen at 11 days, and these were accompanied by the characteristic signs of GVH response usually seen after transplantation of cells from normal allogeneic donors. Transplantation of normal C57BL/10 marrow mixed with small numbers at normal spleen cells resulted in an increase in the number of fatalities among the SJL/J recipients, and an increase in the severity of the signs of GVH response as compared to that seen following engraftment of normal C57BL/10 marrow alone. However, no such increases in fatalities or severity were observed when similar amounts of nude C57BL/10 spleen cells were engrafted along with normal marrow cells into SJL/J recipients. The results suggest that a factor may exist in nude mouse spleen which in allogeneic transplantation can lead to a fatal response suggestive of GVH reaction, but that nude mouse spleen lacks the T cell-related ability to enhance GVH response that has been previously demonstrated following allogeneic transplantation using normal spleen and marrow donors.

Potentiating Effect of Methyl Methane Sulfonate on Friend Virus Leukemogenesis in Vivo

Summary Methyl methane sulfonate (MMS) given ip five hours before Friend Leukemia Virus (FLV) injection enhanced the leukemogenic action of FLV in virus-sensitive SJL/J mice and also in relatively virus-resistant B10SJF1 mice. MMS also decreased the humoral immune response, as measured by plaque forming cell assay. However, the timing of the effect of MMS on the immune system did not coincide with the timing of the MMS related potentiation of leukemia. Hence, it is suggested that the potentiating effect of this chemical on viral leukemogenesis is more likely due to events occurring at the intracellular level than at the level of humoral immune response.

Rauscher leukemia as a model for cancer therapy studies. II. Variation in response of splenic CFU-S between normal and Rauscher leukemic mice following exposure to hydroxyurea

Summary Normal mice and mice with advanced Rauscher leukemia were given a single dose of HU (0.5 mg/g body wt) and evaluated for the effect of the drug on splenic CFU-S 4 and 16 hr later. Exposure to HU reduced the total number of CFU-S for both normal and leukemic mice by 50% at 4 hr. At 16 hr there was no recovery in CFU-S evident in the normal mouse. However, CFU-S levels in the spleens of the leukemic mice had recovered to nearly that existent before exposure to HU. Effects of HU on total splenic mass differed from that on the CFU-S. Recovery of total splenic mass was seen to have begun in normal animals by 16 hr after HU, while in the leukemic animals spleen size had receded further by 16 hr. The data suggest that, as in man, the hematopoietic recovery responses following exposure to chemotherapeutic drugs may be significantly different in Rauscher viral leukemic mice as compared to normal mice. The possible applicability of Rauscher leukemia as a model for leukemia therapy studies is briefly discussed.

Cyclophosphamide/X-ray: Combined mode preparation for transplantation therapy

Abstract Use of total body irradiation (TBI) and/or chemotherapy as a preparation for marrow transplantation in the treatment of leukemia has been only moderately successful in the clinic. Although cyclophosphamide (CY) has shown promise as a marrow ablative agent, leukemia relapses are often found, and optimal therapeutic protocols have not been established. Our transplantation therapy studies of murine leukemia with parental recipients and hybrid donors provide an excellent model for research aimed at improved survival of human transplant patients. Utilizing a murine leukemia induced by a virus, various doses of CY in combination with sub-lethal irradiation were compared to determine the optimal pretreatment for transplantation therapy. Both normal and leukemic mice were engrafted with virus resistant, histocompatible marrow following these preparations, then monitored for survival and long term effects. Leukemic mice were also evaluated for pluripotent as well as myeloid committed stem cells as a measure of the effectiveness of the treatment in elimination of leukemic cells. Leukemic groups were also compared for the percentage and time of leukemia relapse. All CY/X-ray combinations were more effective in elimination of stem cell populations than supralethal TBI alone. However, the best survival was obtained with lethal TBI alone or low dose CY in combination with 550 R.