By John Nash

Organ transplants and blood transfusions are undoubtedly lifesavers: last year around 42,800 people in the US received organ transplants, and nearly 30 million components of blood given in transfusions.

But now some scientists are starting to ask whether something unexpected may be transmitted at the same time as the organ or transfusion.

It’s memory — both in terms of cells transmitting human memory itself (i.e. preferences and character traits), but also individual cells carrying memories of damaging disease traits.

There have been well-publicised stories of people who’ve had organ transplants describing how suddenly they’ve experienced personality changes, developing tastes they’d never before had — in the U.S. a 47-year-old woman had a lung transplant from an 18-year-old and developed a craving for beer and fried chicken.

Now blood transfusions, too, are thought by some scientists to have this kind of effect.

Last month, researchers at Karolinska Institute in Sweden published a major study that suggests a cause of spontaneous brain haemorrhage could be transmitted via blood transfusion.

The study, found that patients who’d received blood from donors who later had recurring brain haemorrhages were more than twice as likely to suffer one themselves.

The researchers drew on a Swedish-Danish database which contains information on donors and patients receiving a transfusion from the 1970s onwards — more than a million patients were included.

The findings suggest some factors that can give rise to spontaneous brain haemorrhages can be spread through blood transfusion. However, as only 0.1 per cent of the donors in the study subsequently suffered recurring brain haemorrhages, this affected a tiny number of patients.

Gustaf Edgren, an associate professor of epidemiology and one of the researchers, said: ‘Blood transfusions are relatively common, which makes negative effects an important public health issue.

‘However, it’s very unlikely that you’d suffer a brain haemorrhage from something transmitted through a transfusion.’

But why is it happening at all? The researchers are now planning to examine samples from the Danish Blood Donor Study biobank to see if they can identify aberrant proteins associated with the condition, which might possibly be damaging blood vessels.

However, other scientists have suggested that something more subtle may be behind this — and some go much further, suggesting that the blood transfusion process may even transfer personality traits from donor to recipient.

Five years ago, for example, a study by Geneva University reported how nearly half of patients reported changes in their behaviour and values after receiving blood transfusions.

The researchers interviewed seven people who’d received blood transfusions for orthopaedic surgery, such as hip replacements, and found three out of seven believed that their personalities had changed. One said he slept and dreamt a lot more than before; and another said his sense of taste had been changed, which he found worrying, saying: ‘I hope that the donor’s blood cannot take over.’

The third patient reported that after the transfusion he felt happier and stronger.

The authors concluded that: ‘Better understanding the frequency and importance of these perceived changes is important as physicians might have to include such information while getting consent for transfusion.’

Such beliefs may simply be dismissed, however scientists studying an emerging field — called cellular memory — say that personality-transference in the wake of organ transplant or blood transfusion is not mere fancy. In a 2019 article, Dr Mitchell Liester, an assistant clinical professor of psychiatry at Colorado University, presented an idea that ‘memories from the donor’s life are stored in the cells of the donated heart and are then “remembered” by the recipient following a transplant’.

If this sounds outlandish, five years ago, scientists reported they’d successfully transplanted memories from one snail into another by transplanting their tissues. The scientists gave mild electric shocks to the tails of a species of marine snail called Aplysia californica. These made the snails’ defensive withdrawal reflex — where they contract to protect themselves from harm — more pronounced.

The shocked snails had learnt to evade the stimulus. Those that received the shocks contracted defensively for 50 seconds when their tails were zapped, while those that hadn’t contracted for only one second. But after the unshocked snails were given transplants from the shocked snails, they contracted for 50 seconds when zapped.

David Glanzman, a professor of biology at the University of California, Los Angeles, who co-authored the study, said the result was ‘as though we transferred the memory’.

He explained that the transplanted cells contained genetic information called RNA, which is involved in various roles including how genes are switched on or off.

Other scientists now suggest that memories may be stored as chemical codes inside the proteins that our DNA is wound around.

But whether this means memories really are transferred in blood transfusions or organ transplants remains to be seen.