Reticulocytes

Excerpt

Reticulocytes are the erythroid cells in the peripheral blood that are in a discrete, penultimate phase of maturation. The nucleus has been removed, usually before the red cells enter the peripheral blood. However, some of the extranuclear RNA remains. This residual RNA generally is lost progressively during the 24 hours after the cell enters the circulation. Reticulocytes thus represent a distinctive cohort of cells, those most recently entering the peripheral blood. Reticulocytes differ from other red cells in that they have a more convoluted shape, and are about 8% larger than the more mature cells. These latter two distinctions are not so clear-cut as is the presence of residual RNA. With the typical Wright's stain used for routine examination, only the earliest reticulocytes with the most residual RNA will be "polychromatophil" (i.e., more bluish than the mature erythrocytes).