The mechanism on offer is passenger cells. According to the 2025 review cited alongside this case, donor-acquired allergies turn up more often after lung and liver transplants than after other solid organs, possibly because both organs carry a lot of B lymphocytes, the cells that make allergen-specific antibodies [18]. Mast cells and basophils are the other candidates: they hold those antibodies on their surface, and when an allergen arrives they release the inflammatory compounds behind anaphylaxis [19].
In this patient the blood work argued for the second group. A test for peanut-specific antibodies came back negative, which her doctors read as evidence that nothing in her body was still making them, and therefore that the reaction came from antibodies already bound to mast cells or basophils inside the graft [20][21]. They then flagged the objection to their own reading: the positive skin-prick test was on her arm, and it is not known whether mast cells or basophils migrate into skin the way circulating antibodies do [22]. So the report documents a transfer and leaves the carrier unresolved.
The trigger list and the test panel also failed to line up. The skin prick flagged peanut and pine nut while clearing tree nuts and coconut [5], yet the episodes followed cereal, a coconut cream pie and an almond candy bar [2][4]. The report notes that none of those foods were known to contain peanut and none were certified peanut-free [6], which leaves trace exposure as the working explanation and makes this partly a kitchen problem. The donor, a boy with a known peanut allergy, had never himself had an anaphylactic reaction, yet his recipient's very first episode with the allergy was anaphylaxis [7][3].
The clearance is the part with operational teeth. No treatment was aimed at the new allergy, the sensitivity shrank on repeat skin-prick tests and had gone by one year [9], and a supervised peanut challenge a few months after that produced no reaction [10]. The treating doctors concluded the donor's sensitized cells had cleared [11], and the 2025 review reports a similar time course in other instances [23]. That timeline suggests screening has a limited window in which it is actually useful.
How often this happens is not something the case can answer. The literature here is counted rather than rated: one prior peanut allergy after a lung transplant before this report was published in 2011, which makes hers the second on record [12][13], and a first solid-organ instance in 1997 after a combined kidney-liver transplant, fourteen years earlier [14][15]. The risk was recognised only a little over a decade before the report, and bone marrow, which manufactures immune cells, was where it was seen first [16][17]. Nobody in this material counts the peanut-allergic donors whose organs transferred nothing, so a usable rate does not exist to weigh the risk against. What is priceable is the ask, and the review authors and the treating doctors converge on the same one: a donor allergy history in the record, and a skin-prick test after transplant [24][25].
