[chris (OP)]

Mark wants to know:

   "Is it possible to have so many blood transfusions that my blood group changes?"

Hopefully everyone here can give us an infusion of knowledge to help us solve Mark's question...

[evan_au]

You could change your blood type by having a bone-marrow transplant....

This doesn't change the blood cells directly, but it changes the cells which produce the blood cells.

However, matching the blood type is probably the easiest part of donor selection...

See: https://en.wikipedia.org/wiki/Hematopoietic_stem_cell_transplantation

[syhprum]

I found this article particularly interesting as the father of my next door neighbour underwent this treatment when he was at deaths door and was surprisingly fit after six months.
sadly his health begins to detiriate but he may well have gained two years of life 

[polly87]

It's impossible. If donor blood has no proper group it may be very dangerous. Special blood groups have their own antibodies inherited antigenic substances on the surface of red blood cells. That's why blood with A group cannot be a donor for B group and conversely. Only having 0 groups you don't have any antigens so you may be a universal donor. Having AB group you have no antibodies and both antigens so you may be the universal recipient.  So, blood transfusion cannot change your blood type, but it can kill you if you won't receive the proper group.

[chris (OP)]

It's impossible. If donor blood has no proper group it may be very dangerous. Special blood groups have their own antibodies inherited antigenic substances on the surface of red blood cells. That's why blood with A group cannot be a donor for B group and conversely. Only having 0 groups you don't have any antigens so you may be a universal donor. Having AB group you have no antibodies and both antigens so you may be the universal recipient.  So, blood transfusion cannot change your blood type, but it can kill you if you won't receive the proper group.

This isn't true. As you have said, group "AB" is the universal recipient, so if a person with group AB blood had a catastrophic haemorrhage and required massive transfusion and he or she received transfusion with group O, group A or group B blood exclusively, for a while (at least until the patient's own marrow caught up) they would test positive for the donor blood group only. Thus there would be an apparent switch in blood group.