Mixed myeloid-Lymphoid colonies in a patient with polycythemia vera

Peripheral blood mononuclear cells from a patient with polycythemia vera were cultured in a methylcellulose system employing human serum. Electron microscopy documented the appearance of mixed colonies containing lymphocytes, granulocytes, megakaryocytes, and erythrocytes. In vitro culture characteristics were similar to those seen for other patients with polycythemia ver, ie, colonies grew in the absence of added erythropoietin or other pathway-specific regulators. Plating efficiency was linearly related to the number of cells plated, which supports the concept that each colony arose from a single cell. The appearance of mixed myeloid-lymphoid colonies points to the existence of a primitive stem cell capable of giving rise to multiple hematopoietic cell lines.