Presence of mast cell precursors in peripheral blood of mice demonstrated by parabiosis.

The presence of mast cell precursors in peripheral blood was examined. The beige C57BL/6 (bgj/bgj, Chediak-Higashi syndrome) mouse was parabiosed with the normal C57BL/6 mouse. Mast cells containing giant granules and originating in the beige partner appeared in the normal parabiont. A comparable proportion of normal-mouse-type mast cells developed in the beige parabiont as well. In spite of the low radiosensitivity of mature mast cells, irradiation of the normal parabiont reduced the proportion of normal-mouse-type mast cells appearing in the beige partner. It was concluded, therefore, that the precursors of mast cells can migrate through the bloodstream.