The splenic microenvironment and self recognition as factors in allograft rejection in rats. A study using indium-111-labeled cells

The beneficial effect of donor-specific transfusions: a review of existing explanations and a new hypothesis based on a relatively unapplied theory of T cell immunoregulation. A regulatory hypothesis in progress

The mechanism by which donor specific transfusions protect a graft from the recipient's immune system is unknown. It is likely that this beneficial mechanism is a subset or distinct exhibition of the general rules governing the regulation of the immune system. This phenomenon provides a strong framework for investigation of immune regulation, considering its potential consanguinity to immune regulation, that it is a paradox representing a manifestation of regulatory rules, and that it provides a wealth of clinical experience and experimentation from which to make inferences. Vital in any exploration of immune regulation, is the promise held in reducing the immune system to its chief elemental regulatory mechanisms and interactions. Strangely, the majority of this consequential work may have already been accomplished by Gershon, Green and colleagues with their elegant demarcation of T cell regulation into suppressor and contrasuppressor pathways. The practical and theoretical implications of this discovery seem to be, for the most part, ignored by mainstream immunology. It is doubtful, based on the quality and quantity of their work, or confirming work by other laboratories that they were inaccurate in their findings. It remains a horrible waste that their discoveries are not in immunology's pantheon of hallowed discoveries and are little used. With all this kept in mind, a comprehensive hypothesis of regulation was put together based mainly on Gershon's portrait of the suppressor and contrasuppressor pathways' contributions to immune regulation and experimentation surrounding the unsolved paradox of donor specific transfusions.

Specific immunosuppression by postoperative infusion of allogeneic spleen cells: requirement of donor major histocompatibility complex expression and graft-versus-host reactivity

BACKGROUND

Donor leukocytes may exert positive immunoregulatory effects on allograft acceptance. Most recent studies have focused on pretreatment protocols. In this study, the effect of postoperative infusion of donor leukocytes on graft survival and the phenotypic and functional requirements for infused cells were investigated in fully major histocompatibility complex (MHC)-mismatched rat heart transplant models.

METHODS

LEW (RT1l) heart grafts were implanted heterotopically into abdomens of LEW.1W (RT1u), and different types of cells were infused postoperatively. Immunohistochemistry was used to evaluate histopathological changes of grafts.

RESULTS

In the absence of any immunosuppressive agents, a single dose of viable donor spleen cells (SC), but not bone marrow cells, was able to prolong heart allograft survival to about 21 days, while they were rejected promptly at day 7 in controls. Infusion of T cell-depleted donor SC, irradiated donor SC or third-party (BN) SC showed no effect on graft survival. Compared with resting cells, neither in vitro nor in vivo prestimulation of infused donor SC improved graft survival. Clinical signs of graft-versus-host reaction were not observed in all above groups. Histology showed remarkable reduction in the severity of graft infiltrate and interleukin-2 receptor-positive cells in grafts of cell-treated animals. Postoperative infusion of SC of F1 generation between different strain combinations showed two requirements for infused cells to be effective: (1) expression of donor-type MHC antigens and (2) strong alloreactivity against the host MHC antigens.

CONCLUSION

Postoperative infusion of viable donor SC can lead to allospecific down-regulation of alloreactivity by a graft-versus-host-associated effect.