White blood cell transfusions do exist and have been used in clinical medicine for more than four decades, but they are far less common than red blood cell or platelet transfusions. Known as granulocyte transfusions, these procedures deliver infection-fighting white blood cells from a donor to a patient whose own supply is dangerously low. The practice remains surprisingly controversial, though, because the largest clinical trial to test it was unable to settle the question of whether it actually works. That tension between a reasonable-sounding idea and thin evidence shapes nearly everything about how, when, and whether these transfusions are given today.
What a Granulocyte Transfusion Actually Involves
When doctors talk about white blood cell transfusions, they almost always mean granulocyte transfusions. Granulocytes are a category of white blood cell that includes neutrophils, the cells your immune system sends first to fight bacterial and fungal infections. A patient with a dangerously low neutrophil count, a condition called neutropenia, can lose this front-line defense entirely. The idea behind a granulocyte transfusion is straightforward: borrow someone else’s neutrophils and infuse them into the patient to bridge the gap until the patient’s own bone marrow recovers.
The challenge starts with the donor. A healthy person’s blood does not carry enough neutrophils to make collection worthwhile on its own. To get a useful dose, donors are pre-treated with a combination of granulocyte colony-stimulating factor (G-CSF) and dexamethasone, a steroid. These drugs temporarily ramp up the donor’s neutrophil production and push those cells into the bloodstream, where they can be harvested through a process similar to platelet donation.1PubMed Central. Efficacy of transfusion with granulocytes from G-CSF/dexamethasone-treated donors in neutropenic patients with infection Early granulocyte collection programs confirmed that community blood banks could run this kind of donor stimulation protocol, though it adds cost and coordination compared to a standard blood donation.2Blood. Phase I/II trial of neutrophil transfusions from donors stimulated with G-CSF and dexamethasone for treatment of patients with infections in hematopoietic stem cell transplantation
Once collected, granulocytes have an extremely short usable life. Neutrophils survive only hours to a couple of days in the body, and they cannot be stored or frozen the way red blood cells or plasma can. This means each transfusion requires a fresh donation, often on a daily schedule. A review of granulocyte transfusion practice noted that the logistical burden of timely donor selection, collection, and infusion remains one of the biggest practical obstacles.3PubMed Central. Granulocyte transfusions: A concise review for practitioners You cannot simply order granulocytes from a blood bank shelf. Every dose is essentially made to order.
Who Actually Gets Them
Granulocyte transfusions are not something a doctor reaches for casually. They have historically been reserved for patients at the extreme end of immune vulnerability: people whose neutrophil counts have been wiped out by chemotherapy, bone marrow transplantation, or congenital immune disorders, and who have developed severe infections that are not responding to standard antibiotics or antifungal drugs.4Cochrane Database of Systematic Reviews. Granulocyte transfusions for treating infections in people with neutropenia or neutrophil dysfunction
Invasive fungal infections are a particularly common trigger. Fungi like Aspergillus can devastate patients with no functioning neutrophils, and antifungal drugs sometimes fail to clear these infections on their own. Granulocyte transfusions have a long track record of being tried in this setting.5PubMed Central. Granulocyte transfusions in the management of invasive fungal infections Case reports continue to describe individual patients with rare, drug-resistant fungal infections who appeared to improve after granulocyte transfusions were added to their treatment, particularly when neutropenia was expected to last a long time.6PubMed Central. Case report: A Saprochaete clavata (Magnusiomyces clavatus) severe infection effectively treated with granulocyte transfusion in a young patient with myeloid sarcoma
The typical candidate, then, is someone undergoing intensive cancer treatment or a stem cell transplant who develops a life-threatening infection while their immune system is essentially offline. This is a small slice of the hospital population, which is part of why granulocyte transfusions remain uncommon. Most patients with infections and low white counts recover with antimicrobial drugs and time; the transfusion is considered only when those approaches are failing.
The Evidence Problem
Here is where things get uncomfortable. For a therapy that has been around for over 40 years, the evidence that granulocyte transfusions work is remarkably thin. The largest randomized trial to address the question, known as the RING study, enrolled neutropenic patients with infections and assigned them to receive either standard antimicrobial therapy alone or the same therapy plus daily granulocyte transfusions from G-CSF/dexamethasone-stimulated donors. The results were sobering: overall success rates were about 42% in the granulocyte group and 43% in the control group, a difference that was statistically meaningless. Even among patients who actually received the treatments as assigned, the rates were 49% versus 41%, still not a statistically significant gap.7PubMed. Efficacy of transfusion with granulocytes from G-CSF/dexamethasone-treated donors in neutropenic patients with infection
The researchers themselves acknowledged a critical limitation: enrollment was only half of what they had planned. Recruiting enough eligible patients proved extremely difficult, which is a recurring theme in studies of rare clinical scenarios. Because the trial was underpowered, it could not rule out a real benefit that was simply too small to detect with the available sample size. So the RING trial did not prove granulocyte transfusions are useless; it just failed to prove they are helpful, which is a frustrating but important distinction.
A Cochrane systematic review of the broader literature reached a similarly ambiguous conclusion, noting the long history of use but the persistent controversy about efficacy.4Cochrane Database of Systematic Reviews. Granulocyte transfusions for treating infections in people with neutropenia or neutrophil dysfunction Practitioners who use granulocyte transfusions tend to argue that properly collected cells, infused promptly and in adequate doses, do appear to help, and that the clinical trial setting may not capture the conditions under which these transfusions work best.3PubMed Central. Granulocyte transfusions: A concise review for practitioners Critics counter that belief based on clinical experience, without rigorous trial data to back it up, is exactly the kind of reasoning that medicine has been trying to move past. Neither side can claim a definitive win here.
Risks and Complications
The uncertain benefit would be easier to justify if granulocyte transfusions carried no significant risk. But they do. The most concerning complication is transfusion-related acute lung injury, or TRALI. This is a serious reaction in which the lungs become inflamed shortly after a transfusion, causing difficulty breathing and sometimes requiring intensive care. While TRALI can happen with any blood product, granulocyte transfusions appear to carry a particular risk because they deliver a large load of immune-active cells. Reported cases in pediatric patients have highlighted how quickly the reaction can develop.8PubMed Central. Transfusion-Associated Acute Lung Injury following Donor Granulocyte Transfusion in Two Pediatric Patients
Another concern is alloimmunization, where the patient’s immune system recognizes the donor’s white blood cells as foreign and produces antibodies against them. This can make future transfusions of any blood product more difficult, because the patient’s body may begin rejecting platelets or other cells that carry similar surface markers. HLA alloimmunization from transfused white blood cells is a well-documented complication that complicates long-term patient management.9PubMed Central. Human leukocyte antigen alloimmunization prevention mechanisms in blood transfusion
There is also an infectious risk. White blood cells can harbor viruses that ride along with the transfusion. Cytomegalovirus (CMV) is the classic example. CMV lives inside white blood cells and can be transmitted through fresh blood products that contain them.10PubMed. Leukocyte depletion and infection by cytomegalovirus For patients who are already severely immunocompromised, picking up a new CMV infection from a transfusion can be dangerous. Donor screening helps reduce this risk but cannot eliminate it entirely.
Why Standard Blood Transfusions Remove White Blood Cells
If you have ever received a red blood cell or platelet transfusion, your white blood cell count was not the goal, and in fact the white blood cells in those products were treated as contaminants. Most blood banks now perform leukoreduction on standard blood products, a process that intentionally filters out the donor’s white blood cells before the product reaches you.11PubMed Central. Leukoreduction for the prevention of adverse reactions from allogeneic blood transfusion
This is done specifically because stray donor white blood cells cause problems. Over the past three decades, research has shown that removing white blood cells from blood components prevents febrile transfusion reactions, reduces alloimmunization against donor tissue markers, and lowers the risk of transmitting CMV.12PubMed Central. Leucoreduction of blood components: an effective way to increase blood safety? Leukoreduction filters physically trap and remove donor white blood cells before the blood product is transfused.13PubMed Central. Role of Leukoreduction of Packed Red Blood Cell Units in Trauma Patients: A Review
The irony is hard to miss. The entire blood banking industry spends considerable effort removing white blood cells from standard products because they cause harm, while a small corner of medicine is simultaneously trying to transfuse as many white blood cells as possible into a different set of patients. Both practices make sense in their own context, but the contrast underscores why granulocyte transfusions are not a mainstream therapy. You are intentionally doing what the rest of transfusion medicine works hard to avoid.
Alternatives That Are More Commonly Used
For most patients with low neutrophil counts, the standard approach is not to transfuse someone else’s white blood cells but to stimulate the patient’s own bone marrow to produce more. This is where growth factors come in. G-CSF (sold as filgrastim) and GM-CSF are drugs approved by the FDA specifically for treating neutropenia. G-CSF promotes the production of neutrophils and is widely used after chemotherapy to speed up the recovery of white blood cell counts.14PubMed Central. G-CSF and GM-CSF in Neutropenia
These drugs are far simpler to administer than a granulocyte transfusion. They come as injections, they do not require a matched donor, and they avoid the TRALI and alloimmunization risks that come with infusing someone else’s cells. For the vast majority of patients whose bone marrow still has the capacity to respond, growth factors are the first and usually the only intervention needed. Granulocyte transfusions enter the picture only when the marrow is so depleted or damaged that it cannot respond to stimulation, which is why they remain a last-resort option.
Granulocyte Transfusions in Newborns
One group that has received particular attention in the granulocyte transfusion literature is newborn infants. Neonatal sepsis combined with neutropenia is a dangerous and sometimes fatal situation, and neonates have immature immune systems that may not respond as readily to growth factor drugs. An early randomized trial compared granulocyte transfusions to intravenous immunoglobulin in newborns with sepsis and neutropenia. The small pilot study suggested a possible benefit of granulocyte transfusions over immunoglobulin therapy in that population.15PubMed. Randomized trial of granulocyte transfusions versus intravenous immune globulin therapy for neonatal neutropenia and sepsis
However, as with adult studies, the evidence base is small. The reported cases of TRALI in children receiving granulocyte transfusions are a reminder that the risks are real in pediatric patients too.8PubMed Central. Transfusion-Associated Acute Lung Injury following Donor Granulocyte Transfusion in Two Pediatric Patients Neonatologists face the same dilemma as adult oncologists: a therapy that might help, with risks that are not trivial, and evidence that is too thin to settle the question. In practice, granulocyte transfusions for neonates remain a case-by-case decision at centers that have the infrastructure to collect and deliver the cells quickly.
Other White Blood Cell Therapies
Granulocyte transfusions are not the only form of white blood cell infusion used in medicine. A separate category involves lymphocytes, a different type of white blood cell that fights viral infections and plays a role in immune surveillance against cancer. Donor lymphocyte infusions have been used to treat viral infections in immunocompromised patients, particularly those who have received a stem cell transplant and are struggling with reactivated viruses like CMV or Epstein-Barr virus.16PubMed Central. Antiviral responses following L-leucyl-L-leucine methyl esther (LLME)-treated lymphocyte infusions: graft-versus-infection without graft-versus-host disease
The concept is similar in spirit but different in execution. Where granulocyte transfusions aim to provide brute-force infection fighting by flooding the body with neutrophils, lymphocyte infusions are more targeted. They can be selected for activity against specific viruses. The main risk with donor lymphocyte infusions is graft-versus-host disease, where the donated immune cells attack the patient’s own tissues. Researchers have worked on techniques to treat the lymphocytes before infusion to reduce this risk while preserving their infection-fighting ability. These therapies occupy their own niche, distinct from granulocyte transfusions, but they illustrate that “white blood cell transfusion” is really an umbrella covering several very different procedures with different goals, risks, and evidence bases.
Lab-Grown Neutrophils and the Future
One of the biggest obstacles to granulocyte transfusions is the supply problem. You need a willing donor who can be stimulated, screened, and collected on short notice, and the resulting cells die within hours. Researchers have been exploring whether neutrophils could instead be grown in a laboratory from stem cells, bypassing the donor entirely. Work using human induced pluripotent stem cells (iPSCs) has shown that it is possible to generate neutrophils in the lab that can circulate in the bloodstream and engulf bacteria in animal models.17PubMed Central. Neutrophils Derived from Genetically Modified Human Induced Pluripotent Stem Cells Circulate and Phagocytose Bacteria In Vivo
The appeal is obvious: iPSCs can theoretically provide an unlimited source of neutrophils without the logistical nightmare of donor recruitment and the constraints of the short shelf life. The cells could potentially be genetically modified to be more effective or to avoid triggering the patient’s immune system. But this work is still in early stages. Producing enough functional neutrophils at clinical scale, proving they work as well as natural donor cells, and navigating regulatory approval are all substantial hurdles. For now, lab-grown neutrophils remain a research project rather than a clinical option, but they represent the most promising path toward making white blood cell transfusions practical on a scale that donor-dependent collection never could.
Why You Probably Will Not Be Offered One
If you are reading this because you or someone you know has a low white blood cell count, the honest answer is that a granulocyte transfusion is unlikely to come up in conversation with your doctor. The procedure exists, it is technically possible, and some patients have clearly been helped by it, but the infrastructure required to do it well is available only at specialized centers. The evidence supporting it has not reached the threshold that would make it a standard recommendation in treatment guidelines. And for most patients with neutropenia, growth factor drugs like G-CSF are simpler, safer, and effective enough to make the question moot.
The patients for whom granulocyte transfusions are seriously considered tend to be in extreme circumstances: prolonged neutropenia expected to last weeks, severe infections unresponsive to every available drug, and a medical team at a facility experienced enough to coordinate the donor logistics on a daily basis. Even then, the decision involves weighing uncertain benefits against concrete risks like TRALI and alloimmunization. It is one of those areas in medicine where the concept is sound, the biology makes sense, and the clinical proof has stubbornly refused to catch up. Forty years of use and we still do not have a definitive trial, in large part because the patients who need it most are rare and sick enough that enrolling them in studies is extraordinarily difficult.