NK cells are required for costimulatory blockade induced tolerance to vascularized allografts.
BACKGROUND
The role of natural killer (NK) cells in organ transplantation is poorly understood because studies link these cells to both regulatory and inflammatory functions. NK cells exacerbate inflammation and adaptive immunity under conditions of allograft rejection, but little is known regarding their roles in allograft tolerance. We test the hypothesis that NK cells have regulatory function and promote tolerance induction to murine cardiac allografts.


METHODS
Murine hearts were transplanted as fully vascularized heterotopic grafts from BALB/c donors into C57BL/6 recipients. Allograft tolerance was achieved using donor splenocyte transfusion + anti-CD40L monoclonal antibody (mAb) before transplantation. The requirement for NK cells in tolerance induction was tested by administering anti-NK1.1-depleting mAb or anti-NKG2D-blocking mAb. Intragraft and peripheral immune cell populations were determined by flow cytometry and immunohistochemistry. CD4 T-cell alloantigen-specific responses and donor-specific alloantibody were also determined.


RESULTS
NK cell-depleted recipients acutely reject allografts despite anti-CD40L blockade, but rejecting recipients lacked alloantibody and alloantigen-specific CD4 T-cell responses. NK cell depletion resulted in elevated numbers of graft-infiltrating macrophages. NKG2D blockade in tolerized recipients did not cause acute rejection but increased macrophage graft infiltration and increased the expression of NKG2D ligand Rae-1γ on these cells.


CONCLUSIONS
Our data show that NK cells are required for tolerance induction in recipients given donor splenocyte transfusion + anti-CD40L mAb. Our data suggest NK cells regulate monocyte or macrophage activation and infiltration into allografts by a mechanism partially dependent on NKG2D receptor-ligand interactions between NK cells and monocytes/macrophages.
Department of Gene and Cell Medicine, Mount Sinai School of Medicine, New York, NY, USA.
William
W
van der Touw
Bryna
B
Burrell
Girdhari
G
Lal
Jonathan S
JS
Bromberg
D019264:Adoptive Transfer; D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage; D055610:Antigens, CD1d / Q000235:genetics / Q000378:metabolism; D000950:Antigens, Ly / Q000276:immunology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D023201:CD40 Ligand / Q000276:immunology; D005434:Flow Cytometry; D019672:Genes, T-Cell Receptor; D006084:Graft Rejection / Q000276:immunology / Q000378:metabolism / Q000517:prevention & control*; D006085:Graft Survival / Q000187:drug effects; D016027:Heart Transplantation / Q000276:immunology*; D007150:Immunohistochemistry; D007166:Immunosuppressive Agents / Q000008:administration & dosage; D007518:Isoantibodies / Q000097:blood; D007519:Isoantigens / Q000276:immunology; D007694:Killer Cells, Natural / Q000187:drug effects / Q000276:immunology* / Q000637:transplantation; D008264:Macrophages / Q000276:immunology / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D009000:Monocytes / Q000276:immunology / Q000378:metabolism; D055651:NK Cell Lectin-Like Receptor Subfamily B / Q000276:immunology; D055655:NK Cell Lectin-Like Receptor Subfamily K / Q000276:immunology; D013154:Spleen / Q000276:immunology; D013997:Time Factors; D023001:Transplantation Tolerance / Q000187:drug effects
D000911:Antibodies, Monoclonal; D055610:Antigens, CD1d; D000950:Antigens, Ly; D007166:Immunosuppressive Agents; D007518:Isoantibodies; D007519:Isoantigens; C527211:Klrb1c protein, mouse; C527086:Klrk1 protein, mouse; D008565:Membrane Proteins; D055651:NK Cell Lectin-Like Receptor Subfamily B; D055655:NK Cell Lectin-Like Receptor Subfamily K; C491217:Raet1c protein, mouse; D023201:CD40 Ligand