Increased clonogenic (CFU-C, PFU-C) populations from bone marrow and spleen of nude mice.

Clonogenic populations from bone marrow and spleen of nude mice and their normal littermates were enumerated in vitro using a methylcellulose supported culture system. This technique allows for the simultaneous quantitation of progenitors of granulocyte-monocyte pathways (colony forming units in culture, CFU-C) and for progenitors of "mesenchymal" elements (plaque-forming units in culture or PFU-C). These populations were distinguished in culture by their growth, characteristics and morphology. CFU-C gave rise to suspended colonies of granulocyte-monocyte composition while PFU-C formed surface-adherent colonies of mesenchymal morphological features (fibroblastic and reticuloendothelial morphology). Significant elevations in the relative and absolute numbers of CFU-C and PFU-C were observed in the bone marrow and spleen of 6 wk old nu/nu mice relative to heterozygous littermates. The results are discussed in terms of non-T cells components involved in cell-medited immunity against neoplastic development.