What are Reticulocytes?

Reticulocytes are immature red blood cells that have one more step to complete before they become full-fledged cells. The name comes from their reticular or mesh-like appearance when viewed through a microscope. The mesh is composed of nucleus strands waiting for export from the cell.

The formation of reticulocytes starts in the bone marrow. They begin as stem cells, the building blocks of all new blood cells. Then they go through a maturing process, eventually becoming red blood cells. Reticulocytes spend about three days in the bone marrow before they enter the bloodstream. Then they take another day to mature into red blood cells.

The only job of a reticulocyte is to mature into a healthy red blood cell. Red blood cells contain hemoglobin and are responsible for carrying oxygen to the tissues. They also take carbon dioxide away, to be exhaled by the lungs. The bone marrow responds to various internal or external challenges by changing the production rate of reticulocytes. Therefore, the amount sometimes varies to meet the needs of the body.

What makes the reticulocyte different than a red blood cell under the microscope is the mesh-like strands of the nucleus. In the blood lab, the strands get dyed with a blue pigment making them easier to see and count. The final count is the percentage of reticulocytes out of one thousand blood cells in the sample.

The doctor will order a reticulocyte count only if other results such as red blood cells or hemoglobin are abnormal. Since reticulocytes are immature red blood cells, doctors need to understand what's affecting their formation. The results will show the efficiency with which the bone marrow is performing. They can also help diagnose conditions that cause abnormal blood cell counts. Lastly, for a person who has had a bone marrow transplant, the reticulocyte count will show how well the new bone marrow performs.

A high reticulocyte count means the bone marrow is compensating for low numbers of red blood cells or hemoglobin. Certain conditions lead to a breakdown, malfunction, or loss of these oxygen-carrying cells, including autoimmune disorders. Therefore, the bone marrow has to produce high numbers of reticulocytes to maintain enough oxygen in the body.

A low reticulocyte count means the bone marrow is not working correctly and the body is producing too few of the stem cells that create reticulocytes. Several conditions lead to an inappropriate bone marrow response, such as infections, tumors, or cirrhosis of the liver. A doctor requires more information on other symptoms and may need to conduct further tests to determine the overarching cause.

marina_ua / Getty Images

People with cancer or chronic illness often use treatment modalities that can affect bone marrow function and create lower reticulocyte counts. Also, kidney issues can affect the production hormones that stimulate the bone marrow. Vitamin deficiencies and a condition called aplastic anemia can cause low reticulocyte counts. High reticulocytes indicate that there's internal bleeding or red blood cells are getting destroyed in the bloodstream.

Reticulocytes are part of a blood cell cycle that begins and ends in the bone marrow, where the production of stem cells that develop into many blood cells, including reticulocytes, takes place. Then they mature into red blood cells that live for 120 days. Old red blood cells are broken down by the liver, spleen, and bone marrow. Waste products filter through the intestines for removal. Lastly, essential components such as iron and amino acids get recycled back to the bone marrow to help make new blood cells.

Maintaining healthy reticulocyte counts requires preventing conditions that affect their production. A healthy diet rich in vitamins and minerals helps prevent deficiencies that affect blood cell production. Getting treatment for internal bleeding and other chronic conditions is also essential. Preventing kidney problems is important since this organ produces a hormone that stimulates blood cell production. Lastly, detecting and treating the causes of anemia will maintain healthy levels of all blood cells including reticulocytes.