Donor lymphocytes transferred with the graft to kidney recipients. Potential for establishing microchimerism

After solid organ transplantation donor lymphocytes have been shown to survive and multiply in the organ recipient for a prolonged period. It is not clear whether this chimerism detected is the result of immunosuppression or the cause of allograft acceptance. The number of cells transferred, as well as the type of cells, and the degree of activation are likely to be of importance for the establishment of microchimerism. The cells that are flushed out of the vascular tree may be of particular importance since when an antigen primarily bypasses or secondarily avoids organised lymphoid collections, the immune system in the recipient may remain or become "indifferent" to its presence. In the present study we examined the amount of residual donor blood cells that we could flush out from the vascular tree of living donor kidneys and cadaveric donor kidneys immediately prior to transplantation, with special emphasis on T and B lymphocytes. Our study shows that perfusion of donor kidneys just prior to transplantation releases from 0.1 to 1.8x10(6) B-lymphocytes, with an average of 0.7x10(6) and from 0.5x10(6) to 2.6x10(6) T-lymphocytes, with an average of 1.8x10(6), for CD kidneys, and somewhat less for LD kidneys. These cells would otherwise have been flushed out into the organ recipient's circulation, where they might play a role in the establishment of microchimerism.