Colony inhibition of fibroblasts from chimeric dogs mediated by the dogs' own lymphocytes and specifically abrogated by their serum

Nine canine irradiation chimeras were studied between 173 days and 7.5 years after 1200 to 1500 r of total body irradiation and transplantation of allogeneic bone marrow. Skin fibroblasts from chimeras and normal dogs were tested for colony inhibition by exposure to sera and peripheral blood lymphocytes from both chimeric and normal dogs. Lymphocytes from the chimeric dog were found to inhibit colony formation by its "own" fibroblasts while lymphocytes from other chimeras or from normal dogs did not. Serum from the chimera specifically abrogated this inhibitory effect. These results indicate that the immunological "tolerance" of the chimeric dog is mediated in vivo by blocking serum factors.

Hemophilia: role of organ homografts

The concentration of factor VIII and partial thromboplastin times became normal and have remained normal for 140 days after orthotopic tranplantation of a normal liver to a hemophilic dog. Transplantation of a normal spleen into a hemophilic recipient did not result in a significant increase in factor VIII although the splenic graft was viable for at least 47 days. Transplantation of normal marrow to a lethally irradiated hemophilic dog did not result in an increase in factor VIII during 34 days of observation.

Studies on the partition of iron in bone marrow cells

Canine marrow cells were incubated with transferrin-bound (59)Fe, and the partition of cellular iron was studied by chromatographic and gel filtration methods. Splitting-off of iron from the stromal fraction was avoided by lysing the cells in Tris HCl buffer at pH 8.6. Cellular iron was divided into four major compartments: stroma, microsomes, main hemoglobin, and fraction I. The iron in fraction I was found in ferritin, heme proteins, and low molecular weight iron. With incubation times of 3-10 min, (59)Fe appeared promptly in the main hemoglobin. The entry of (59)Fe into ferritin paralleled that of hemoglobin but was smaller in amount. When the marrow cells were incubated with (59)Fe for 15-20 min and reincubated without radioactive iron, movement of (59)Fe into main hemoglobin was observed, and essentially all this iron came from the particulate fraction (stroma, mitochondria, and microsomes). In these chase experiments there was no change in the total quantity of (59)Fe in ferritin. There was no evidence of a significant hemoglobin precursor other than low molecular weight iron. DEPENDING UPON CONCENTRATION, LEAD WAS OBSERVED TO INHIBIT CELLULAR IRON METABOLISM AT SEVERAL POINTS: uptake of iron by the cell, movement of iron from stroma to the soluble intracellular compartment, and synthesis of hemoglobin. The most pronounced inhibitory effect of lead was always on hemoglobin synthesis with an increase in ferritin: hemoglobin ratio. Bipyridine appeared to trap intracellular ferrous iron and to inhibit synthesis of both hemoglobin and ferritin. It was concluded that iron moves from the stroma into the soluble intracellular compartment as low molecular weight iron, probably as a complex of ferrous iron with low molecular weight components of the cytoplasm, that serves as the source of iron for both hemoglobin and ferritin synthesis.