Connective tissue mast cells (CTMC) and mucosal mast cells (MMC) are apparently different, but the ontologic relationship between these two types of mast cells was unclear. We investigated the relationship by combining in vivo and in vitro techniques. Although bone marrow-derived mast cells developed in suspension culture resemble MMC, they acquired histochemical, electron microscopical, biochemical and immunological characteristics of CTMC after the transfer into the peritoneal cavity of genetically mast cell-deficient WBB6F1-W/Wv mice. On the other hand, when single peritoneal mast cells (typical CTMC) of WBB6F1-+/+ mice were injected into the stomach wall of WBB6F1-W/Wv mice, CTMC appeared in the muscularis propria and MMC in the mucosa. These results suggest that CTMC and MMC may interchange and that their phenotypes are determined by the anatomical microenvironment in which the final differentiation occurs.
The fate of mast cells after degranulation was investigated. Purified peritoneal mast cells of WBB6F1-+/+ mice were sensitized with monoclonal anti-dinitrophenol (DNP) IgE antibodies and stimulated with DNP conjugated with human serum albumin. Mast cells were vitally stained with neutral red, and highly degranulated mast cells were identified under a phase-contrast microscope and individually picked up with the micromanipulator. When these highly degranulated mast cells were individually plated in methylcellulose, their potential to produce a cluster or a colony was comparable to that of morphologically intact mast cells. Moreover, when highly degranulated mast cells were injected into the skin of genetically mast cell-deficient WBB6F1-W/Wv mice, the proportion of injection sites at which mast cell clusters appeared was comparable to the value observed when morphologically intact mast cells were injected. The present result indicates that proliferative potential of mast cells is not reduced by their degranulation.
The fate of mast cells after degranulation was investigated. Purified peritoneal mast cells of WBB6F1-+/+ mice were sensitized with monoclonal anti-dinitrophenol (DNP) IgE antibodies and stimulated with DNP conjugated with human serum albumin. Mast cells were vitally stained with neutral red, and highly degranulated mast cells were identified under a phase-contrast microscope and individually picked up with the micromanipulator. When these highly degranulated mast cells were individually plated in methylcellulose, their potential to produce a cluster or a colony was comparable to that of morphologically intact mast cells. Moreover, when highly degranulated mast cells were injected into the skin of genetically mast cell-deficient WBB6F1-W/Wv mice, the proportion of injection sites at which mast cell clusters appeared was comparable to the value observed when morphologically intact mast cells were injected. The present result indicates that proliferative potential of mast cells is not reduced by their degranulation.
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.
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