Stem Cell Transplant Engraftment Simulator

Transplant Setup

Donor CD34+ dose 4.0 ×10⁶/kg

HLA match 10/10 (100%)

Conditioning Intensity

Immunosuppression 70%

Engraftment Status

Set parameters and press Start.

ANC (neutrophils)

0 /µL

Platelets

0 ×10⁹/L

Donor chimerism

Niche occupancy

How it works

After conditioning (chemo/radiation) clears host marrow, infused donor CD34+ cells home to marrow niches and expand logistically until niches saturate:

dN/dt = r · N · (1 − N/K)
N0 = dose × homing(match)
homing = 0.30 + 0.60 × match
K = niche capacity × conditioning intensity

Lower conditioning intensity leaves more resident host cells occupying niches, so K is smaller and engraftment is slower but the regimen is gentler on the patient. A weaker HLA match reduces homing efficiency and raises the daily probability of a T-cell mediated graft rejection event, which collapses the donor population — immunosuppression suppresses that probability.

ANC(t)  ≈ 1500 · (N/K)^1.5,  lag ≈ 9 days
Plt(t)  ≈ 220  · (N/K)^1.8,  lag ≈ 13 days
P(reject per day) = 0.06 × (1 − match) × (1 − suppression)

Dose — more infused cells raise the starting donor population N0, shortening time to threshold.
HLA match — controls homing efficiency and rejection risk; 10/10 is a full sibling/matched-unrelated match, lower values are haploidentical or mismatched grafts.
Conditioning — sets how much marrow "real estate" (K) is freed for the graft before infusion.
Immunosuppression — post-transplant drugs (tacrolimus, MMF, etc.) that suppress host-vs-graft rejection.
Neutrophil engraftment is clinically defined as the first of 3 consecutive days with ANC ≥ 500/µL — the simulator flags that day live.

Day 0

Empty niche Donor-occupied niche Mature cell output

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