In the ccea bio textbook it says regarding transplanting tissue 'transplant rejection can also involve the action of B-lymphocytes and antibodies. Eg if the blood of a donor and a recipient is different this can produce an immune response involving antibodies. Normally tissue matching is accurate so rejection by B-lymphocytes in this situation is unlikely to occur'. I understand that in the case of blood donation, b lymphocytes are involved as it is humoral-mediated (body fluid) but I don't understand how B lymphocytes would ever be involved in tissue transplantation as they only react to body fluids and tissue/ organ transplant isn't fluid. Any help appreciated thanks!