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Stem cell products and apheresis

16 min

Skills you'll build4 skills
  • Calculate a viable CD34-positive cell dose per kilogram of recipient weight
  • Recalculate the viable-cell dose after each progenitor cell processing step
  • Choose red-cell and plasma groups after a major or minor ABO-mismatched transplant
  • Match an apheresis procedure to what it removes and what replaces it

At the bench: Check component identity, storage, and suitability before issue

Try first

Try first

A hematopoietic progenitor cell (HPC) product contains 2.4 × 10⁸ viable CD34-positive cells and 5.6 × 10¹⁰ total nucleated cells. The recipient weighs 80 kg. What CD34 dose does the product provide?

Keep going to see the reasoning.

Keep going to see the reasoning.

Keep going to see the reasoning.

Right. Keep going to follow the reasoning.

Keep going to see the reasoning.

Get the idea

Use the explanation to check your first decision.

The CD34 dose

The viable CD34-positive count is the standard measure of progenitor cell dose. Viable CD34-positive dose (cells/kg) = total viable CD34-positive cells ÷ recipient weight (kg). When only total CD34-positive cells are given, multiply by the measured viable fraction once, first. Required total cells = protocol target (cells/kg) × recipient weight (kg), with expected processing loss as a separate allowance on that total. For adult peripheral-blood collections, generally accepted minimums are 2 × 10⁶ CD34-positive cells/kg for an autologous transplant and 4 × 10⁶/kg for an allogeneic one. Each program sets its own target.1

Processing losses

Red-cell or plasma reduction, freezing, thawing and washing each lose some cells. The laboratory measures recovery and viability after each step and recalculates the dose before release.1,2 Cryopreservation commonly uses dimethyl sulfoxide (DMSO) at 5% to 10% with controlled-rate freezing. Washing a thawed product lowers DMSO and hemolysate exposure, and some viable cells are lost.1,2

ABO-mismatched transplants

Donors are chosen by HLA, so ABO-mismatched grafts are common. In a major mismatch the recipient has antibody against the donor's red cells, such as a group O recipient with a group A donor. In a minor mismatch the donor's plasma or lymphocytes carry antibody against the recipient's red cells. A bidirectional mismatch has both.3 Group O red cells and group AB plasma are compatible with every donor-recipient pairing. Donor-type red cells are given only after donor red-cell production is confirmed and the recipient's anti-A or anti-B is gone.3

Apheresis

ProcedureRemovesReturns or replaces
Plasma exchangeThe patient's plasmaAlbumin, plasma or both
Red-cell exchangeThe patient's red cellsDonor red cells, at the same volume
LeukapheresisWhite cellsThe patient's red cells and plasma
PlateletpheresisPlateletsThe patient's red cells and plasma

Albumin restores volume and contains no clotting factors or immunoglobulins. After repeated exchanges with albumin, a falling fibrinogen and a prolonged prothrombin time (PT) show depletion. The laboratory reports coagulation results before and after each exchange.4

Follow the bench demonstration

Sources for this step
References
  1. Sureda A, Corbacioglu S, Greco R, et al, eds. The EBMT Handbook: Hematopoietic Cell Transplantation and Cellular Therapies. 8th ed. Springer; 2024. doi:10.1007/978-3-031-44080-9
  2. Foundation for the Accreditation of Cellular Therapy; Joint Accreditation Committee ISCT-Europe & EBMT. FACT-JACIE International Standards for Hematopoietic Cellular Therapy Product Collection, Processing, and Administration. 9th ed, version 9.1. Effective February 2, 2026. Accessed September 27, 2026.
  3. Matteocci A, Pierelli L. Immuno-hematologic complexity of ABO-incompatible allogeneic hematopoietic stem cell transplantation. Cells. 2024;13(10):814. doi:10.3390/cells13100814
  4. Bloch EM, Campbell-Lee S, McKenna DH Jr, Montemayor-Garcia C, Schwartz J, Shaz B, Storry J, eds. Technical Manual. 22nd ed. AABB; 2026.

Watch one

Read each decision and its explanation.

An allogeneic peripheral-blood HPC product is collected for a 72-kg recipient. The program's target is 4 × 10⁶ viable CD34-positive cells/kg. Flow cytometry counts 3.6 × 10⁸ total CD34-positive cells, and 92% of them are viable.

What dose does the product provide, and does it meet the target?

  1. Required total = 4 × 10⁶ cells/kg × 72 kg = 2.88 × 10⁸ viable CD34-positive cells.

    The target sets the number of cells the product must contain.

  2. Viable CD34-positive cells = 3.6 × 10⁸ × 0.92 = 3.31 × 10⁸.

    Only viable cells count toward the dose, and the viable fraction is applied once, first.

  3. Dose = 3.31 × 10⁸ ÷ 72 kg = 4.6 × 10⁶ cells/kg.

    A dose per kilogram divides the cells by the recipient's weight.

  4. Compare: 4.6 × 10⁶/kg is above the 4 × 10⁶/kg target, and 3.31 × 10⁸ cells is above the 2.88 × 10⁸ required.

    Any processing loss comes off this number, so the margin above the target matters.

The product provides 4.6 × 10⁶ viable CD34-positive cells/kg, which meets the target before any processing.

Practice this skill

Your turn

Problem 1 of 3 · Hints available

A graft contains 1.8 × 10⁸ viable CD34-positive cells for a 60-kg recipient. What dose does it provide before any further processing loss?

Correct. The dose is 1.8 × 10⁸ ÷ 60 = 3.0 × 10⁶ cells/kg, which is then compared with the transplant protocol's own target.

Incorrect. Dividing 1.8 by 60 gives 0.03, so the result is 0.03 × 10⁸, which is 3.0 × 10⁶. Keeping 10⁸ ignores the two powers of ten the division removes.

Incorrect. This multiplies the cell count by body weight. A dose in cells/kg divides the count by the kilograms.

Hint
  1. A dose in cells/kg divides the cell count by the weight in kilograms.
  2. Divide 1.8 by 60 first, then keep track of the power of ten.

Review CD34 dose and the collection target

Problem 2 of 3 · Hints available

After several daily plasma exchanges with albumin replacement, a patient's fibrinogen has fallen and the prothrombin time (PT) is prolonged. Why can plasma be ordered for part of the next replacement?

Incorrect. The exchange removes the patient's own plasma whichever fluid replaces it. The replacement fluid determines only what is given back.

Incorrect. Allergic reactions occur most often with plasma replacement and only occasionally with albumin, which is one reason albumin is the routine replacement.

Correct. Each exchange removes clotting factors with the patient's plasma, and albumin returns none. The falling fibrinogen and prolonged PT show the depletion, and coagulation results before and after each exchange show when plasma is needed for part of the volume.

Hint
  1. Ask what each exchange removes along with the patient's plasma.
  2. Compare what albumin replaces with what plasma replaces.

Review Adverse effects of apheresis

Problem 3 of 3 · On your own

A marrow product for a 60-kg recipient contains 2.7 × 10⁸ viable CD34-positive cells when it arrives. Red-cell reduction recovers 80% of the viable CD34-positive cells. What dose remains, in 10⁶ viable CD34-positive cells/kg?

Show the answer

3.6 × 10⁶ cells/kg

Cells after reduction = 2.7 × 10⁸ × 0.80 = 2.16 × 10⁸. Dose = 2.16 × 10⁸ ÷ 60 kg = 3.6 × 10⁶ cells/kg. The arrival count gives 4.5 × 10⁶/kg, which overstates the dose infused.

Review Laboratory processing

Use it

Read the case evidence, then make each decision. The step is complete without it.

  • Tomasz Summers, 52, a carpenter who builds birdhouses for his grandchildren, is group A.
  • Sixty days ago he received a peripheral-blood HPC graft from his group B sister.
  • The ward orders one red-cell unit and one unit of plasma.
  • Today's ABO typing: his red cells show a mixed field with anti-A and with anti-B. His plasma gives 0 with A1 cells and 2+ with B cells.
Decision 1 of 3

Which red cells do you issue?

His plasma still reacts 2+ with B cells. His own anti-B would destroy group B red cells.

Switched to donor-type red cells too early

After an ABO-mismatched transplant, recipient isoagglutinins and mixed red-cell populations can persist. Donor-type red cells given before donor erythropoiesis and loss of recipient anti-A or anti-B are confirmed can be hemolyzed, which is why group O red cells and AB plasma are the usual interim choices.

His sister's lymphocytes in the graft can make anti-A, and his new marrow is making group B cells. Group A red cells risk hemolysis from donor-derived anti-A.

Group O red cells carry neither A nor B antigen. Neither his anti-B nor any anti-A from donor lymphocytes can react with them.

Review ABO incompatibility in HPC transplantation

Decision 2 of 3

Which plasma do you issue?

Group AB plasma has no anti-A and no anti-B. It does not react with his remaining group A cells or with the donor-derived group B cells.

Group A plasma contains anti-B, which would react with the group B cells his new marrow is making.

Group B plasma contains anti-A, which would react with his remaining group A red cells.

Review ABO incompatibility in HPC transplantation

Decision 3 of 3

When can his red-cell support move to group B?

The change is based on his test results. He is at day 60 and still has anti-B.

The mixed field shows his own group A cells are still present, and the 2+ reaction with B cells shows his anti-B. Both must be resolved under the program's transition policy.

His red cells are expected to convert to the graft's group B. His plasma still contains anti-B today.

Switched to donor-type red cells too early

After an ABO-mismatched transplant, recipient isoagglutinins and mixed red-cell populations can persist. Donor-type red cells given before donor erythropoiesis and loss of recipient anti-A or anti-B are confirmed can be hemolyzed, which is why group O red cells and AB plasma are the usual interim choices.

Review ABO incompatibility in HPC transplantation

His plasma still reacts 2+ with B cells, so his own anti-B is present, and the mixed field shows that his group A cells are still circulating. Group O red cells and group AB plasma are compatible with both cell populations until both findings resolve.

For reference

Sources checked