A granulocyte transfusion (GT) is a specialized medical procedure involving the infusion of a concentrated unit of white blood cells called granulocytes. These cells, including neutrophils, eosinophils, and basophils, are part of the body’s innate immune system. Neutrophils are the most abundant and infection-fighting component. The purpose of this transfusion is to temporarily support patients whose bodies cannot produce enough cells to combat a severe infection. GT is a relatively rare, supportive therapy requiring significant coordination between blood banks, donors, and the medical team.
The Purpose and Need for Granulocyte Transfusion
Patients typically require a granulocyte transfusion when they are experiencing severe, life-threatening infections and their body’s defenses are compromised. The primary medical condition necessitating this treatment is severe neutropenia, defined as an absolute neutrophil count (ANC) below 500 cells per microliter of blood. This profound immune suppression often occurs as a side effect of intensive treatments like chemotherapy or hematopoietic stem cell transplantation, where the bone marrow’s ability to generate new blood cells is temporarily suppressed.
The transfusion is reserved for patients with confirmed or suspected bacterial or fungal infections that have not responded to aggressive, appropriate antimicrobial therapy for 24 to 48 hours. The goal is to provide an immediate influx of functioning immune cells to help clear the infection until their own bone marrow naturally recovers. Without this temporary immune support, a spreading infection can rapidly overwhelm the patient.
The decision to proceed is made when there is a reasonable expectation that the patient’s bone marrow will eventually recover, making the treatment a bridge to recovery. The transfused neutrophils are meant to act as an auxiliary force, targeting pathogens that antibiotics or antifungals alone have failed to eliminate. GT may provide benefit as an adjunctive therapy in these complex clinical scenarios.
The Donor and Collection Process
Granulocyte collection is specialized and differs significantly from a standard blood donation due to the low number of these cells naturally circulating in the bloodstream. To ensure a sufficient therapeutic dose, the donor undergoes a process called mobilization. This involves administering medications to stimulate the bone marrow to release a high number of granulocytes into the peripheral blood.
The donor is typically given an injection of Granulocyte Colony Stimulating Factor (G-CSF), a growth factor that encourages the production and release of white blood cells. An oral corticosteroid such as dexamethasone is often given, which works in conjunction with G-CSF to further enhance the cell yield. This preparatory regimen is necessary because the target dose for an effective transfusion is high, often requiring a minimum of \(1.0 \times 10^{10}\) granulocytes per unit.
The actual collection is performed using a technique called apheresis, where the donor’s blood is drawn from one arm and passed through a specialized machine. Inside the apheresis machine, the granulocytes are separated from the rest of the blood components through centrifugation and the addition of a sedimentation accelerator like hydroxyethyl starch. The remaining components, including red blood cells and plasma, are then returned to the donor through a separate line. The entire apheresis procedure for a single unit usually takes between two and four hours.
Transfusion Administration
The administration of a granulocyte transfusion must occur quickly after collection because these white blood cells have a very short functional lifespan. Ideally, the transfusion is completed within six hours of harvesting, and the product cannot be stored for longer than 24 hours. This limited shelf life necessitates immediate coordination between the donor center and the patient’s care team, meaning granulocytes are collected only on an “as-needed” basis.
Before infusion, the product must be irradiated to prevent a complication called transfusion-associated graft-versus-host disease (TA-GVHD). Irradiation deactivates T-lymphocytes present in the collected product, which could otherwise attack the immunocompromised recipient’s tissues. The granulocytes are then infused intravenously, usually through a standard blood administration set containing a filter.
The typical volume for an adult apheresis unit is approximately 300 to 400 milliliters. The infusion process is monitored closely, with the duration often lasting several hours. Because the transfused granulocytes are cleared from circulation within six to eight hours, the patient often requires daily transfusions for a series of five or more consecutive days. This repeated dosing continues until the infection is resolved or the patient’s own neutrophil count recovers to a safe level, typically above 500 cells per microliter.
Potential Risks and Considerations
Granulocyte transfusions carry a higher risk of adverse reactions compared to transfusions of other blood components. One of the most common complications is a febrile non-hemolytic transfusion reaction, characterized by fever and chills. To mitigate these common reactions, patients are often given pre-medications such as acetaminophen or antihistamines prior to the infusion.
A more serious concern is the risk of pulmonary complications, which can range from mild difficulty breathing to Transfusion-Related Acute Lung Injury (TRALI). TRALI causes acute respiratory distress and is a potentially fatal reaction where the donor’s antibodies react with the recipient’s white blood cells, leading to fluid accumulation in the lungs.
There is also a risk of alloimmunization, where the recipient develops antibodies against the donor’s Human Leukocyte Antigens (HLA) found on the white blood cells. The development of HLA antibodies can complicate future transfusions, potentially causing platelet refractoriness or interfering with the success of a later stem cell transplant. Furthermore, because the product contains red blood cells, it must be ABO-compatible and crossmatched to prevent a hemolytic transfusion reaction. Due to the urgent nature and short shelf life of the product, infectious disease testing may not be fully complete at the time of issue, which presents a small risk of transfusion-transmitted infections.