Increased soluble CD154 (CD40 ligand) levels in xenograft recipients correlate with the development of de novo anti-pig IgG antibodies.
BACKGROUND
De novo anti-pig antibodies are associated with acute humoral xenograft rejection. We explored the relative efficacy of CD40/CD154-pathway blockade versus CD28/B7-pathway blockade in the prevention of de novo anti-pig IgG antibodies in xenograft recipients.


METHODS
After α1,3-galactosyltransferase gene-knockout pig artery patch xenotransplantation, recipient baboons received no immunosuppression (IS; n=3), or anti-CD154mAb-based (n=5) or CTLA4-Ig-based (n=5) IS. CD4 T-cell and CD20 B-cell numbers in blood were determined. Serum anti-pig IgG antibodies and serum soluble (s)CD154 levels were measured. In lymph nodes, germinal center formation was examined and numbers of proliferating cells were evaluated by Ki-67 staining.


RESULTS
After transplantation, with no IS, CD4 T-cell and CD20 B-cell numbers were increased, but were reduced by IS.In lymph nodes, with no IS, there was enhanced germinal center formation, which was significantly reduced by anti-CD154mAb-based (P<0.01) or CTLA4-Ig-based (P<0.01) IS. With no IS, there was strong expression of Ki-67-positive cells in lymph nodes, indicating extensive cellular proliferation. Ki-67-positive cells were significantly reduced by anti-CD154mAb-based (P<0.05) but not by CTLA4-Ig-based IS. High mean levels of sCD154 were detected with no IS (3324 pg/mL), in comparison to naive control baboons (214 pg/mL). With anti-CD154mAb-based IS, sCD154 was reduced to less than 1 pg/mL and with CTLA4-Ig-based IS to 65 pg/mL. There was significant positive correlation between sCD154 and anti-pig IgG levels (P<0.01).


CONCLUSIONS
In xenograft recipients, anti-CD154mAb may reduce class-switching of anti-pig antibodies by binding both T-cell surface CD154 and circulating sCD154, thus preventing subsequent stimulation of B cells and activation of lymphoid follicles in secondary lymphoid tissues.
1 Thomas E. Starzl Transplantation Institute, Department of Surgery, University of Pittsburgh, Pittsburgh, PA. 2 Department of Surgery, Transplantation and Advanced Technologies, Vascular Surgery and Organ Transplant Unit, University Hospital of Catania, Catania, Italy. 3 Department of Immunology, University of Pittsburgh, Pittsburgh, PA. 4 Revivicor, Blacksburg, VA. 5 Address correspondence to: Mohamed B. Ezzelarab, M.D., Thomas E. Starzl Transplantation Institute, University of Pittsburgh Medical Center, Starzl Biomedical Science Tower, E1551, 200 Lothrop Street, Pittsburgh, PA 15261, USA.
Mohamed B
MB
Ezzelarab
Burcin
B
Ekser
Kumiko
K
Isse
Hayato
H
Iwase
Adrian E
AE
Morelli
David
D
Ayares
David K C
DK
Cooper
D000818:Animals; D000906:Antibodies / Q000097:blood* / Q000276:immunology; D000911:Antibodies, Monoclonal / Q000494:pharmacology / Q000627:therapeutic use; D001158:Arteries / Q000637:transplantation*; D001402:B-Lymphocytes / Q000473:pathology; D015496:CD4-Positive T-Lymphocytes / Q000473:pathology; D023201:CD40 Ligand / Q000097:blood* / Q000187:drug effects / Q000276:immunology; D049109:Cell Proliferation; D006084:Graft Rejection / Q000276:immunology* / Q000517:prevention & control; D064593:Heterografts; D056724:Immunity, Humoral / Q000276:immunology; D007074:Immunoglobulin G / Q000097:blood* / Q000276:immunology; D007166:Immunosuppressive Agents / Q000494:pharmacology / Q000627:therapeutic use; D008198:Lymph Nodes / Q000473:pathology; D023421:Models, Animal; D010215:Papio; D013552:Swine; D014180:Transplantation
D000906:Antibodies; D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D007166:Immunosuppressive Agents; D023201:CD40 Ligand