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SUMMARY A histological study was carried out on the spleen and bone marrow colonies of (DS X C57BL) F1 hybrid mice. Parental (DS) lymph node cells injected into F1 hybrid mice after sublethal irradiation eradicated the endogenous colonies of the host. The host colonies disappeared earlier in the spleen than in bone marrow. When parental spleen or bone marow cells were added to the lymph node cells, colonies appeared in the spleens of F1 hybrid mice whose endogenous colonies were eradicated by parental lymph node cells. The fact that the number of colonies was directly proportional to the number of added spleen cells suggested the parental origin of these colonies. In this case, myeloid colonies outnumbered erythroid colonies (erythroid to myeloid colony ratio of below 0.5). The differentiation pattern was different from those of endogenous colonies, exogenous colonies coming from spleen cells of hybrid donors and exogenous colonies which appeared in F1 hybrid mice injected with parental bone marrow cells only (erythroid to myeloid colony ratio of above 2.5). The result of the graft-versus-host reaction caused by parental immunocompetent cells affects the differentiation of parental colony-forming cells.
Kitamura et al. (Tue,) studied this question.