Abstract
In vitro 14-day cultures of peripheral blood mononuclear cells from hairy cell leukemia patients consistently showed the presence of hematopoietic stem cells giving rise to multilineage colonies containing a high proportion of lymphoid cells associated with the myeloid and erythroid progenitors. These stem cells are not the hairy cells but appear to be pluripotent lymphomyeloid primitive stem cells persisting in this leukemia. Interferon alpha c or beta 1 did not inhibit the growth of these colonies, as they did the growth of colonies of normal hematopoietic progenitors, but markedly decreased the ratio of lymphoid to myelomonocytic cells, by increasing the formation of monocytes and other nonlymphoid cell types in these multilineage colonies. Interferon gamma did not have the same effects on differentiation.