In vitro immunogenicity of cadaver donor bone marrow cells used for the induction of allograft acceptance in clinical transplantation.
BACKGROUND
The cascade of immunological effects brought about by donor bone marrow cell (DBMC) infusions to induce allograft acceptance in clinical transplantation is not fully understood. Aside from acting as immune responding and regulatory cells, the infused DBMC also may sensitize the recipient to the donor antigens.


METHODS
To analyze this stimulatory activity of DBMC, in vitro mixed lymphocyte cultures (MLC) and cell-mediated lymphocytotoxicity (CML) culture systems analogous to the transplant model with DBMC infusion were used.


RESULTS
When responding peripheral blood lymphocytes (PBL) from normal volunteers were placed in culture with suspensions of Ficoll-purified, T cell-depleted, un-irradiated allogeneic DBMC (NT-DBMC), a reaction was seen in both MLC and CML. However, when compared to allogeneic spleen cells as stimulating cells, the responses to NT-DBMC were of markedly lower magnitude and were not seen when the NT-DBMC was irradiated (3000 R). When responding PBL were stimulated with either NT-DBMC that had been previously cultured with irradiated cells from the responders for 1 week (activated NT-DBMC), NT-DBMC further depleted of CD15+ and glycophorin A-positive cells (NT-LP/DBMC), or purified CD34+ and CD2+ DBMC subsets, stronger lymphoproliferative and cytotoxic responses were observed. Moreover, these responses were not abrogated by irradiation of the stimulating DBMC subpopulations. Depletion of antigen-presenting cells by positive selection of CD3+ cells from the responding PBL abrogated MLC and CML reactivity, even when purified NT-LP/DBMC, the most stimulatory cells, were used. This latter observation was in contrast to the responses seen with cultures containing allogeneic stimulating spleen cell populations. This indicated the requirement for indirect alloantigen presentation, i.e., the failure of these DBMC to stimulate by direct alloantigen presentation. NT-DBMC was able to stimulate responding PBL in secondary MLC and CML responses with an equivalent magnitude, irrespective of whether the stimulators were spleen cells or NT-DBMC. Finally, the MLC and CML responses were inhibited by tacrolimus (FK506), mycophenolic acid (MPA), and cyclosporine (CsA) in a dose dependent manner, in contrast to previously observed refractoriness of DBMC preparations to these agents if DBMC was tested as responder cells or in modulatory assays.


CONCLUSIONS
These results indicate that DBMC are able to function as effective in vitro stimulators, but only by indirect antigen presentation, and that the immune responses mediated by them can be down-regulated by their own inherent suppressive nature, an effect that can be enhanced by the presence of immunosuppressive drugs.
Mathew
J M
JM
Department of Surgery, University of Miami School of Medicine, Florida 33136, USA.
Carreno
M
M
Fuller
L
L
Ricordi
C
C
Kenyon
N
N
Tzakis
A G
AG
Miller
J
J
Esquenazi
V
V
D000917:Antibody Formation / Q000502:physiology; D001854:Bone Marrow Cells / Q000187:drug effects / Q000276:immunology* / Q000502:physiology; D016026:Bone Marrow Transplantation; D002102:Cadaver; D003602:Cytotoxicity, Immunologic; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D066298:In Vitro Techniques; D007959:Lymphocyte Culture Test, Mixed; D008214:Lymphocytes / Q000502:physiology; D016377:Organ Transplantation; D013154:Spleen / Q000166:cytology; D014019:Tissue Donors; D019172:Transplantation Conditioning; D014184:Transplantation, Homologous
D007166:Immunosuppressive Agents