The big divide: your cells, or a donor's

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Every transplant falls on one side of a single line: are the healthy stem cells your own, or someone else's? That one question separates the two great families of transplant, and almost everything else follows from it.

If you're brand new to the topic, our plain-English intro to what a bone marrow transplant is → is a good place to start first.

Autologous transplant — your own cells

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In an autologous transplant, you are your own donor. Your stem cells are collected and frozen while they're healthy, then given back after high-dose chemotherapy has cleared out the disease. The stored cells rebuild the marrow the treatment wiped out.

Because the cells are your own, there's no matching, no waiting for a donor, and no risk of the new cells attacking your body. That makes it the simplest and safest type, usually with a shorter stay. It's used mainly for multiple myeloma and certain lymphomas.

Its limit is that the returned cells bring no new immune system to fight off any remaining disease — which is why some conditions need a donor instead.

Allogeneic transplant — cells from a donor

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In an allogeneic transplant, the healthy cells come from someone else. It's used when your own marrow can't be trusted to grow back healthy — in leukaemia, thalassemia, sickle cell disease, and aplastic anaemia.

Donor cells bring a powerful advantage, especially against blood cancers: the new immune system can recognise and attack any remaining disease. The trade-off is that the cells must match closely, and the new immune system can sometimes react against the body — graft-versus-host disease, which the team works to prevent and manage.

Where allogeneic transplants really differ is in the donor. That's where the sub-types come in.

Matched sibling donor

A brother or sister who is a full tissue-type match is the ideal donor. Outcomes are best and the process is most straightforward. The catch is odds — any full sibling has only about a one-in-four chance of matching, so many patients don't have one.

Haploidentical (half-matched) donor

When there's no full match, a half-matched relative — usually a parent or child — can often be used instead. This has been a genuine breakthrough: because a parent is always a half-match to their child, haploidentical transplants mean almost every patient now has a possible donor. Indian units are especially experienced with them.

Matched unrelated donor (MUD)

When no family donor works, a matched stranger can be found through a donor registry. This route takes longer and costs more, because of the search and the collection and shipping of the cells — but it means very few patients are left without an option.

Umbilical cord blood

Stem cells can also come from banked umbilical cord blood. Cord units don't need to match as tightly, which helps when no other donor is found, and they're used mostly in children, since a single unit holds a limited number of cells.

The types side by side

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For how each type compares on cost and risk — and which one a diagnosis usually calls for — see the fuller guide: Autologous vs allogeneic transplant →

Two other terms you might hear

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Beyond "whose cells," transplants are sometimes described in two other ways, which can add to the confusion. Here's what they mean.

By where the cells are collected. The same healthy stem cells can be gathered from the hip bone (a bone marrow harvest), from a vein after a few days of injections (peripheral blood, now the most common way), or from cord blood. This is why "bone marrow transplant" and "stem cell transplant" usually mean the same thing.

By the strength of the conditioning. The chemotherapy given before a transplant can be full-intensity (myeloablative), which is powerful but demanding, or gentler (reduced-intensity), which suits older or less robust patients. The choice balances hitting the disease hard against what the patient can safely tolerate.

So which type is "best"?

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There isn't a best type in the abstract — only the right type for a particular disease and patient. The diagnosis decides whether you need your own cells or a donor's; the donor situation decides which allogeneic route; and the patient's age and health guide the conditioning strength.

That's genuinely reassuring: it isn't a decision families have to agonise over. A transplant specialist matches the type to the case, aiming for the best chance of a cure with the least risk.

Common questions

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