The term reticulocyte is applied to the stage of maturation which begins after the expulsion of the nucleus of the late normoblast but before the red cell has become biconcave and no longer contains any organelle.

The reticulocytes are identified by means of the methylene blue stain which both colours and aggregates ribosomal remnants ( RNA) which persist in the young red cell. In these photos all the cells showing ribosomes (aggregates of), with deep blue coloration, are the reticulocytes.

The reticulocytes can nowadays be identified by automated flow cytometric techniques. These methods allow identification of 3 reticulocyte sub-populations and produce an index of immature reticulocytes as defined by their content of RNA. The clinical significance of this distinction remains to be identified.


The reticulocyte is a cell which is deformable. This allows it to traverse the walls of the marrow capillaries. It can thus alter its shape to cross from the bone marrow into the bloodstream.

In the blood the reticulocytes have a median survival of 48 hours during which time they finish synthesising haemoglobin and then become mature red cells. At this stage the cell still contains the organelles needed for this synthesis. These disappear by autophagocytosis. In the mature erythrocyte there are no organelles at all.