By: Dr. Amrit Kaur Kaler, MD., Assistant Professor of Pathology, MVJ Medical College & Research Hospital, Bangalore.
What are Neocytes ?
Neocytes are new red cells which comes from bone marrow afresh. They have a longer life span, say about 120 days in the circulation. These young red cells survive longer after transfusion and therefore may contribute to the extension of intervals between transfusions.
They are of lesser weight as compared to the older cells (gerocytes). Because of this property, these cells can be separated and collected, selectively, by apheresis method from a blood donor.
The mainstay of managing thalassemia major patients is repeated blood transfusions. An attempt should be made to maintain hemoglobin level above 10-12 g/dL to ensure active life and adequate growth. Group and type specific, fresh, triple saline washed, packed red cell transfusions are the most desired form of component therapy. However, patients are exposed to a higher number of donors, with a consequent risk of transmission of infections, and risk of developing alloantibodies. Iron overload results in multiple organ dysfunction due to hemosiderosis and hemochromatosis. At present only desferrioxamine is available as iron chelating agent in parenteral form.
A complementary approach to the problem is the use of blood units enriched with young red cells (neocytes), which reduce the transfusional frequency (one transfusion in three months instead of once a month) and thereby diminish the risk of iron overload.
Neocyte preparation system
A pheresis procedure is devised to isolate young red cells by centrifugation using the Fenwal CS 3000 continuous flow cell separator. Donors’ blood is anticoagulated and the young red cell harvesting is carried out over 4 hours at a constant rotor speed of 500 rpm. Large numbers of white cells and platelets are collected with the red cells, but cryopreservation and subsequent washing removes 99% of these contaminating cells. At the completion of this process, a product yielding 70% of the total hemoglobin content of a standard frozen/deglycerolized red cell unit is produced. Neocyte enrichment is evaluated by reticulocyte count and the mean red cell age is estimated from erythrocyte pyruvate kinase, an age-dependent enzyme inside the RBCs.
However, this procedure is costly and needs a lot of expertise.
It must be emphasized that, despite the high cost of this blood product, the efficiency of this transfusion technique, represents an important progress by reducing blood consumption.
It is a hopeful treatment for chronic anaemias especially thalassemia major patients.
-> This kind of apheresis is faster then platelet apheresis. Normally it takes 10 minutes for 1 complete cycle. A maximum of 8 cycles is done but can be stopped at any number of cycle depending upon the need.
-> Approximately 40 ml of red cells is collected in each cycle. This enables the blood bank to bleed exact amount of blood needed for the patient.
-> Little amount of citrate enters the donor's body similar to platelet apheresis. Hence after donation the donor should not consume any citric content for next 24 hours and calcium tablets should be given while donating.
-> Its advisable to consume milk after donation.