Canine cyclic haematopoiesis: bone marrow adherent cell influence of CFU-C formation.

Canine cyclic haematopoiesis (CH) appears to be a multipotential stem cell defect, possibly due to an intrinsic marrow defect. The in vitro adherent marrow cells of the cyclic haematopoietic (CH) dog were cultured as underlayers beneath normal dog nonadherent marrow cells. The marrow granulocyte-committed colony forming units (CFU-C0 of the normal dog nonadherent cells were cyclically influenced by the CH adherent cell underlayers. The CH adherent cells collected on the ninth or tenth day following the onset of neutropenia did not stimulate CFU-C formation while those collected on the sixth day stimulated as many as 108 colonies. The CH adherent cells collected on other cycle days supported increased CFU-C formation with the exception of cycle day 3 which inconsistently stimulated growth. These data show that the CH marrow in vitro adherent cells alternately stimulate and inhibit in vitro granulopoiesis of normal dog marrows.