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SURVIVAL OF HOST MAST CELLS AFTER ESTABLISHMENT OF HEMATOPOIETIC CHIMERISM BY GRAFT‐VERSUS-HOST REACTION IN NONIRRADIATED F1 HYBRID MICE

Since the tissue mast cell has been shown to be progeny of the multipotential hematopoietic stem cell (CFU-S), and the CFU-S is a sensitive target of graft-versushost (GVH) reaction, we examined whether or not the mast cell is also the target of GVH reaction. Giant granules of C57BL/6-bgJ/bgJ mice were used as a marker of donor cells. When 108 spleen cells of C57BL/6-bgJ/bgJ mice were injected into nonirradiated (C57BL/6 × CBA) F1 hybrid mice, erythrocytes and neutrophils became of donor type in about one-half of the recipient mice. In the bone marrow and spleen of the chimeric mice, the CFU-S was of donor type as well. In contrast, mast cells of host type remained in many tissues of the chimeras. Moreover, mast cell precursors with capabilities of proliferation and differentiation were preserved in the skin of chimeras. The present results suggest that the effect of systemic GVH reaction on mature mast cells and the mast cell precursor fixed in the skin is significantly less severe than that on the CFU-S itself.