4.3 Granulocytes, Leukoreduced, and Irradiated Components

4.3 Granulocytes, Leukoreduced, and Irradiated Components

Quick Answer: Granulocytes are collected by apheresis from G-CSF- and/or steroid-stimulated donors, stored at 20–24 °C without agitation, and expire in 24 hours. Irradiate them, never leukoreduce them, and crossmatch if red cells contaminate the product. Leukoreduction means residual WBC < 5 × 10^6 per unit (U.S.); prestorage filtration is preferred and reduces febrile reactions, HLA alloimmunization, and CMV risk (CMV-safe). It does not prevent TA-GVHD. Irradiation delivers 25 Gy to the center and ≥ 15 Gy to any part of the container. Irradiated red cells expire 28 days from irradiation or on the original outdate, whichever is first. Irradiate for intrauterine transfusion, neonates, congenital immunodeficiency, Hodgkin lymphoma, purine analogs, HLA-matched or blood-relative directed units, and all granulocytes.

These three I.D. items are modifiers and one specialty product. The exam will mix them: a stem that asks for CMV-safe inventory wants leukoreduction (or a CMV-seronegative unit), not irradiation. A stem that asks for TA-GVHD prevention wants irradiation, not a filter.

Granulocytes — collect, irradiate, hang, do not filter

Granulocytes for transfusion are an apheresis product, not a centrifuged whole-blood buffy coat in modern U.S. practice. Donors are typically stimulated with G-CSF, a corticosteroid (dexamethasone or prednisone), or both so the circulating neutrophil count is high enough to yield a useful bag. AABB’s usual yield target is at least 1.0 × 10^10 granulocytes. Unstimulated collections rarely meet that number and are the wrong mental model.

Storage is 20–24 °C without agitation for 24 hours. Neutrophils are metabolically fragile; agitation shears them, and refrigeration impairs function. The Circular and AABB storage tables both treat this as a transfuse-as-soon-as-possible product, not overnight inventory. Ship at room temperature, not on wet ice and not on a platelet agitator.

Two processing rules are absolute:

• Never leukoreduce. A leukocyte-reduction filter is designed to remove the very cells you just collected. Issuing granulocytes through a bedside LR filter is a manufacturing/administration error.
• Always irradiate. The product is packed with viable lymphocytes. TA-GVHD prevention is mandatory.

The bag also contains a large red-cell contaminating dose — often enough to look like a small RBC unit. Therefore:

• Select ABO-compatible granulocytes whenever possible.
• Perform a serologic crossmatch if the red-cell content meets the facility’s “RBC-contaminated component” rule (it usually does).
• RhD matters for D-negative recipients of childbearing potential the same way it matters for red cells.

CMV-seronegative or leukoreduced cellular components are a separate CMV strategy for other products. You cannot leukoreduce granulocytes to make them CMV-safe, so CMV-seronegative donors are considered for CMV-negative recipients. Infuse through a standard 170–260 µm clot filter, not an LR filter. Clinical indications (severe neutropenia with uncontrolled bacterial or fungal infection) are Chapter 17; here the identity of the product is the point.

Worked scenario. A G-CSF/dexamethasone-stimulated apheresis granulocyte unit is collected at 10:00, irradiated, and found to have a visible red-cell layer. It is stored at 22 °C without agitation, ABO/Rh compatible, and crossmatch-compatible. Expiration is 10:00 the next day. Running it through a leukoreduction filter, placing it in the platelet agitator, or refrigerating it at 4 °C are all process failures.

Leukoreduced components — residual WBC < 5 × 10^6

U.S. leukoreduction is a residual leukocyte count below 5 × 10^6 per unit. That is the specification that allows an ISBT-128 leukocyte-reduced product code. Europe uses a tighter < 1 × 10^6 cutoff; do not put the European number on a U.S. exam item unless the stem is comparative. AABB also requires ≥ 85% recovery of the original red-cell content so the filter does not destroy the dose (Chapter 3.4).

Prestorage filtration (in-line at the collection center, or early in component prep) is preferred. Leukocytes that sit in a 1–6 °C red-cell bag or a 20–24 °C platelet bag release cytokines (IL-1, IL-6, TNF) that drive febrile non-hemolytic reactions. Removing the cells before storage prevents that accumulation. Bedside filtration can still remove intact leukocytes but does not remove cytokines already in the supernatant and does not, by itself, let you claim a validated residual count unless the process is QC’d that way. Universal prestorage leukoreduction is standard U.S. practice for red cells and platelets.

What leukoreduction does:

• Reduces febrile non-hemolytic transfusion reactions.
• Reduces HLA alloimmunization (important for platelet-dependent patients).
• Reduces CMV transmission enough that a leukoreduced unit is accepted as CMV-safe, equivalent in practice to a CMV-seronegative unit for most indications.

What leukoreduction does not do:

• It does not prevent TA-GVHD. Residual lymphocytes below 5 × 10^6 can still engraft in a vulnerable recipient. That is an irradiation problem.
• It does not prevent allergic or anaphylactic reactions (those are plasma-protein problems → wash).
• It does not replace antigen-negative red cells, hemoglobin S-negative units, or bacterial-risk control for platelets.

Plasma can be collected as leukoreduced if the process meets the same residual-WBC specification, but the clinical payoff is mainly on cellular components.

Irradiated components — 25 Gy center, ≥ 15 Gy everywhere

Irradiation inactivates donor T lymphocytes so they cannot engraft and cause transfusion-associated graft-versus-host disease. The validated dose is 25 Gy (2500 cGy) to the midplane/center of the container and at least 15 Gy to any other part of the bag. Cesium-137, cobalt-60, and X-ray irradiators are all acceptable if the dose map meets that pair. A sticker without a dose map is not irradiation QC.

Red-cell dating shortens because irradiation accelerates the potassium leak and membrane injury: the new outdate is 28 days from the date of irradiation or the original outdate, whichever comes first. A 42-day AS unit irradiated on day 30 keeps the original day-42 date (12 days left < 28). The same unit irradiated on day 5 expires on day 33 (28 days from irradiation). Irradiation is not an open-system entry and is not a 24-hour wash clock. Platelets and granulocytes keep their original short dates; you do not extend a platelet to 28 days by irradiating it.

Irradiate for these BB-level indications:

• Intrauterine transfusion and neonates, especially premature infants and those receiving exchange transfusion or who previously received IUT.
• Congenital T-cell immunodeficiency (SCID and related disorders).
• Hodgkin lymphoma (the classic acquired cellular-immunity indication).
• Recipients of purine analogs and related lymphocytotoxic drugs — fludarabine, cladribine, deoxycoformycin (pentostatin), clofarabine, bendamustine — and other T-cell-depleting agents such as alemtuzumab on facility lists.
• HPC transplant recipients (allogeneic and, by most policies, autologous around the transplant window).
• HLA-matched platelet or red-cell products and directed donations from blood relatives (shared HLA haplotypes make TA-GVHD more likely).
• All granulocyte units.

Irradiation is not required for every red-cell transfusion, is not a CMV strategy, and is not a substitute for leukoreduction. Many units are both leukoreduced and irradiated; each modifier solves a different problem. Extracellular potassium can be high in irradiated red cells stored several days — a manufacturing reason some neonatal and IUT units are irradiated just before issue or washed after irradiation, which is a therapy-chapter detail built on this dating rule.

Exam traps. Granulocytes: room temperature, no agitation, 24 hours, irradiate, never leukoreduce, crossmatch the red cells. Residual WBC is < 5 × 10^6, not 5 × 10^8. CMV-safe is leukoreduction; TA-GVHD prevention is irradiation. Irradiated RBC dating is the earlier of 28 days and the original outdate, not a fresh 42-day clock.