Total lymphoid irradiation and cyclophosphamide as preparation for bone marrow transplantation in severe aplastic anemia

A new combination of total lymphoid irradiation and cyclophosphamide was used prior to bone marrow transplantation in an attempt to achieve decreased rejection rates and graft-versus-host disease. Nine previously transfused patients with severe aplastic anemia received marrow from an HLA-identical, MLC-compatible sibling following this preparative regimen. There were no episodes of graft rejection, and only one patient developed graft-versus-host disease. Of the 9 patients, 7 (78%) are surviving with a median follow-up of 400 days. The excellent results of this pretransplant combination of total lymphoid irradiation and cyclophosphamide warrants application of this regimen to a larger series of patients.

Cardiac allograft survival in rhesus primates treated with combined total lymphoid irradiation and rabbit antithymocyte globulin

Eighteen abdominal heterotopic cardiac allografts were performed in outbred rhesus primates. For immunosuppression seven animals received six 100-rad/day total lymphoid irradiation (TLI) doses the week preceding transplant and three 3-mg/kg i.m. rabbit antithymocyte globulin (RATG) doses on postoperative days -1, 0, and +1; five animals were given this RATG dose but no irradiation; three were given TLI alone; and three were given no immunosuppressive therapy. Circulating T lymphocyte counts were monitored in all animals (rosettes). Graft survival in the combined TLI-RATG therapy group (169 +/- 15 days) was significantly greater than in untreated (11 +/- 1 days), RATG alone (22 +/- 12 days), or TLI alone (38 +/- 6 days) treated animals (P less than 0.001, 0.0001, and 0.001, respectively). The animals receiving combined TLI-RATG therapy also achieved significantly greater and more prolonged T lymphopenia than that obtained in the other three groups. Six of seven cardiac allografts placed in animals receiving TLI-RATG therapy were removed electively before cessation of electrical activity; however, in four of these rejection pathology was noted. Thus, it seems that combined TLI-RATG therapy may be of benefit in the management of transplant recipients, but its use will probably not abolish these patients' requirements for immunosuppressive maintenance measures.

Selective lymphoid irradiation. I. An approach to transplantation

The kinetics, distribution, and radiobiologic effects of palladium (Pd)-109-hematoporphyrin were determined in the rat. In addition, we studied the effect on rat heart allograft survival of Pd-109-hematoporphyrin, with and without antilymphocyte serum (ALS). A single sublethal dose of Pd-109-hematoporphyrin (up to 36 muCi/kg) resulted in the following: predominant concentration in lymphoid tissue and proximal bone marrow, complete central and proximal bone marrow ablation with preservation of distal bone marrow, massive depletion of lymphocytes from lymph nodes and spleen, an 80% reduction in peripheral blood lymphocytes which was completed by the addition of ALS, full recovery of lymphoid tissue and blood cellularity within 60 days of administration of radionuclide, and a 100% animal survival rate. This method of selective lymphoid irradiation (SLI) prolongs indefinitely Fisher cardiac allografts in Lewis recipients and significantly prolongs cardiac allograft survival across major histocompatibility barries (ACI to Lewis or to Fisher). Specific tolerance to donor strains was demonstrated by the acceptance of Fisher skin by Lewis recipients carrying 150-day-old Fisher hearts. Third party (ACI) skin allografts were rapidly rejected by the same animals. Further studies of SLI in larger animals are required to determine the optimal safe dose of SLI in man.

[Effect of space flight on the course of radiation lesions in the lymphoid organs of rats]

The spleen, thymus and inguinal lymph nodes of rats exposed to a prolonged (24 hours) irradiation at a dose of 800 rad on the 10th day of the 20-day space flight aboard the biosatellite Cosmos-690 were examined histologically and cytologically. The lymph organs showed the changes typical of radiation-induced lesions. They did not display an aggravating or modifying effect of space flight factors on the development of radiation-induced lesions in lymph organs. It is emphasized that radiation-induced lesions at the above irradiation dose may mask weightlessness-induced effects in lymph organs.

[Decrease in the radiation effect in the lymphoid organs of animals adapting to altitude]

Adaptation to altitude hypoxia exerts a positive effect on the cell density of lymph organs of gamma-irradiated animals. It also reduces radiation degradation of DNA, its availability to DNase in the nuclear chromatin and disorders in the activity of DNA polymerases. The role of inhibition of radiation-induced degradation of chromatin DNA in the protective effect of altitude adaptation on the cell density of lymph organs is discussed.

Transplantation tolerance in adult rats using total lymphoid irradiation: permanent survival of skin, heart, and marrow allografts

Lewis rats given total lymphoid irradiation (TLI) accepted bone marrow allografts from AgB-incompatible donors. The chimeras showed no clinical signs of graft-versus-host disease. Skin allografts from the marrow donor strain survived for more than 150 days on the chimeras. However, third-party skin grafts were rejected promptly. Although heart allografts survived more than 300 days in Lewis recipients given TLI and bone marrow allografts, detectable levels of chimerism were not required for permanent survival.

[Combined action of weightlessness and ionizing radiation on the body of rats (based on data from morphological studies)]

The combined effect of weightlessness and ionizing radiation (24 hour exposure to Cs-137 at a total dose of 800 rad) was investigated morphologically in Cosmos-690 flight, synchronous and vivarium rats. Irradiation-induced lesions prevailed in both groups of rats. Comparative study of changes in flight and control rats showed that weightlessness and other space flight factors did not induce any new, previously unknown effects as compared with the exposure on the Earth; they did not exert a significantly aggravating effect on the development of radiation-induced lesions.

Radiosensitivity of T and B lymphocytes. IV. Effect of whole body irradiation upon various lymphoid tissues and numbers of recirculating lymphocytes

Groups of 10-week-old female CBA/J mice were exposed in whole body fashion to 0,5,50, and 500 rads and sacrificed in serial fashion 1,3,5,7,9,15, and 30 days after irradiation for morphologic evaluation of thymus, spleen, lymph node, and Peyer's patch, and assessment of the relative numbers of thymus-derived (T) and bone marrow-derived (B) cells in these tissues. The absolute and relative numbers of recirculating T and B cells mobilizable by thoracic duct cannulation were also determined and compared with similar determinations with respect to peripheral blood lymphocytes. B cell depletion occurred more quickly and was more pronounced in spleen and lymph node than T cell depletion at all three exposure doses. Depletion of T and B cells was roughly equal in peripheral blood and thoracic duct lymph. When present, regeneration of the T cell component occurred more rapidly than did B cell restoration. The latter often was incomplete at the time of the final sacrifice (day 30). PHA-responsive and Con A-responsive cells also appeared to differ with respect to the kinetics of cell death after whole body irradiation.

Long-term survival of skin allografts in mice treated with fractionated total lymphoid irradiation

Treatment of recipient Balb/c mice with fractionated, high-dose total lymphoid irradiation, a procedure commonly used in the therapy of human malignant lymphomas, resulted in fivefold prolongation of the survival of C57BL/Ka skin allografts despite major histocompatibility differences between the strains (H-2d and H-2b, respectively). Infusion of 10(7) (C57BL/Ka x Balb/c)F1 bone marrow cells after total lymphoid irradiation further prolonged C57BL/Ka skin graft survival to more than 120 days. Total lymphoid irradiation may eventually prove useful in clinical organ transplantation.

Radiation modifying effects of meso-tetraphenyl porphyrins

The radiation modifying effects of a series of the metal chelates of meso-tetra(p-carboxyphenyl) porphine has been investigated using a human lymphoid cell line, RPMI 1788. These studies revealed that Ni and Zn porphyrins were effective radiation sensitizers at concentrations as low as 10-9M. Further studies with Zn porphyrin showed it to be almost equally effective when added immediately after irradiation and partially effective when added up to 90 minutes post irradiation, suggesting that it may be acting by interfering with a repair mechanism.

Lymphoid tissue architecture. Experimental analysis of the origin and distribution of T-cells and B-cells

The distribution of bone marrow-derived cells, thymus-derived cells and tissue-bound immunoglobulin was examined using indirect immunofluorescence. It was demonstrated that primary follicle small lymphocytes are bone-marrow derived in the absence of the thymus, they lack thymus-associated antigens, and bear high concentrations of surface-associated immunoglobulins. Thymus-antigen positive cells make up the majority of, if not all, diffuse cortex lymphocytes, do not bear concentrations of surface immunoglobulin detectable in this system, are found as rare cells in primary follicles, and are present in germinal centres. A mechanism is proposed for the thymus—bone marrow interaction in the immune response.

Synergy among lymphoid cells mediating the graft-versus-host response. IV. Synergy in the GVH reaction quantitated by a mortality assay in sublethally irradiated recipients

A mortality assay was used to quantitate graft-versus-host (GVH) reactions in sublethally irradiated (400 R) neonatal (C57BL/6 x BALB/c)F(1) recipients of BALB/c lymphoid cells from various tissues. The probit of the 35 day cumulative per cent of mortality was a linear function of the logarithm of the cell inoculum for any tissue; reactivities of different tissues fell on a series of parallel lines. Peripheral blood leukocytes (PBL), the most active cells, were about 30 times as active as thymocytes, the least active cells studied; femoral lymph node cells and spleen cells were about 23 and 8 times as reactive as thymocytes, respectively. The average survival time of recipients of thymocytes who eventually died was nearly a week longer than that of recipients of comparably lethal numbers of PBL, lymph node, or spleen cells. Mixtures of PBL and thymocytes gave levels of 35 day mortality significantly greater than those expected if the reactivities of the mixture had been merely the sum of the reactivities of the components measured separately, thereby confirming in any assay independent of host splenomegaly the synergistic interaction of thymocytes and PBL in the GVH reaction. Both populations of cells in the mixture had to be allogeneic to the host in order to observe this synergy. The kinetics of cumulative mortality observed for mixtures of PBL and thymocytes were indistinguishable from those seen with thymocytes alone, indicating activation of the latter cell type. Finally, comparison of the relative abilities of different cell populations to cause splenomegaly on the one hand and lethal runting on the other has raised the possibility that expression of different effector functions of cell-mediated immune reactions may in fact be initiated by distinct cells.

The role of passenger leukocytes in the anomalous survival of neonatal skin grafts in mice

The anomalous survival of neonatal C3H skin grafts on CBA mice is correlated with the emigration of passenger leukocytes from the graft vasculature. Thus, newborn homografts whose leukocyte populations are eliminated by X-irradiation or by transient sojourn on an intermediate adult C3H host, do not display prolonged survival. Moreover, the continued presence of the newborn grafts is not requisite to the maintenance of the unresponsive state, an observation consonant with the demonstration that CBA mice bearing long-term neonatal C3H skin grafts are leukocyte chimeras. In contrast, neonatal male C57 skin grafts may persist on C57 females after heavy irradiation of the donor, or after passage on an intermediate adult male host. In addition, tolerance is broken by removal of long-persistant newborn grafts from hitherto unresponsive females, and chimerism is not detectable in female C57 mice tolerant of infant male isografts. Finally, leukocytes of neonatal C3H origin, inoculated subcutaneously into CBA males, may occasionally render these animals unresponsive to subsequent adult C3H skin homografts, whereas those taken from infant C57 males usually sensitize their adult female hosts. Thus, passenger leukocytes are implicated in the extended survival of C3H neonatal homografts on CBA recipients, but not in the persistence of H-Y-incompatible neonatal skin isografts on C57 females.