| Abstract: | When bone marrow cells of (WB X C57BL/6)F1-+/+ (WBB6F1-+/+) and WB-+/+ (WB) mice were directly injected into the skin of genetically mast cell-deficient WBB6F1-W/Wv mice, mast cell clusters appeared at the injection sites. However, the number of WB bone marrow cells necessary for appearance of mast cell clusters was significantly larger than when bone marrow cells of WBB6F1-+/+ mice were used. When WB bone marrow cells were mixed either with WB thymus cells or with silica particles, the proportion of injection sites at which mast cell clusters appeared increased to the level that was observed after the injection of the same number of WBB6F1-+/+ bone marrow cells. When suckling WBB6F1-W/Wv mice of less than or equal to 18 days of age were used as recipients, bone marrow cells of WBB6F1-+/+ and WB mice produced mast cell clusters with a comparable efficiency. Both syngeneic thymus cells and silica particles are known to abrogate the hybrid resistance that is observed in the spleen against parental hematopoietic stem cells. The hybrid resistance in the spleen is not detectable in suckling mice, either. Thus, the poor growth of mast cell precursors in the skin and the poor growth of hematopoietic stem cells in the spleen seem to be regulated by the same mechanism. |
