reticulocyte Immature precursor of the red blood cell in which the remains of the nucleus are visible as a reticulum. Very few are seen in normal blood as they are retained in the marrow until mature, but on remission of anaemia, when there is a high rate of production, reticulocytes appear in the bloodstream (reticulocytosis).

reticulocyte (ri-tik-yoo-loh-syt) n. an immature red blood cell (erythrocyte). Reticulocytes normally comprise about 1% of the total red cells.