A leukopak is a leukocyte-enriched apheresis collection: a bag of concentrated white cells drawn from one donor in a single session, sold to laboratories that need far more primary human cells than a tube of blood can give. Fresh means it has not been cryopreserved, which buys viability and function and imposes a shipping window measured in hours rather than months. This page is about what the specification actually controls, and what to ask a supplier before the courier is booked.
What a leukopak is, and how fresh differs from cryopreserved
Apheresis passes a donor's blood through a separator that keeps the white cell fraction and returns the rest, so a single collection yields a population that would take many ordinary draws to assemble. A fresh pack goes out at room temperature or cool, unfrozen, and is expected on the bench within a day or so. A cryopreserved pack is banked in aliquots and shipped on dry ice or in vapour phase, which decouples your experiment from the donor's calendar at the cost of a freeze and thaw the cells have to survive. Fresh wins on function and on anything where a thaw artefact would be read as biology; cryopreserved wins on scheduling and on comparing across time.
Donor specification is most of the price
The bag is largely a commodity; the donor is not. Price moves with how narrowly the donor is specified: age and sex, a particular HLA type, a serology or infectious disease profile, a mobilised or unmobilised collection, a disease state or a matched healthy control, a repeat draw from the same person months later. A supplier holding a recallable donor panel can offer the last of those, and that is usually what the premium is for. Decide which of those attributes your experiment genuinely needs, because each one narrows the pool and each narrowing shows up in the quote.
The shipping window, and what arrives
A fresh collection is on a clock from the moment the separator stops. Agree the collection time, the expected arrival window, the temperature the pack travels at and who is responsible when a flight slips. Ask what the release criteria are and whether you see them before the pack leaves rather than after it lands. On arrival, count and check viability yourself before anything else, and keep that reading: it is the only number that tells you whether the pack you paid for is the pack you received.
Consent, ethics and the paperwork that travels with the cells
Human material for research arrives with an evidence trail or it should not arrive at all: documented informed consent covering research use and, where relevant, commercial use and genetic analysis; an ethics or review board approval for the collection protocol; and a donor identifier that is coded rather than named. In the United States the collection sits inside the tissue and cell framework and, where the research involves identifiable private information, the Common Rule. A supplier who cannot show that file for this pack is not cheaper, only riskier.
Questions people ask about fresh leukopak
How long is a fresh leukopak usable?
Suppliers specify a window rather than a hard expiry, and it is short: plan to process on arrival, on the same day where the assay allows it. Function declines before viability does, so a good count is not proof the cells will still respond.
Fresh or cryopreserved leukopak?
Fresh where the readout is a functional response or where a thaw artefact would be indistinguishable from the effect you are measuring. Cryopreserved where you need the same donor across months, or where the experiment cannot be scheduled around a collection.
What donor details can a supplier give me?
Coded demographics, the serology and screening profile, the collection method and, from a recallable panel, the ability to order the same donor again. Anything that would identify the person is not available and should not be asked for.