Donor-Specific Antibodies Are Produced Locally in Ectopic Lymphoid Structures in Cardiac Allografts

Cardiac allograft vasculopathy (CAV) is a transplant pathology, limiting graft survival after heart transplantation. CAV arteries are surrounded by ectopic lymphoid structures (ELS) containing B cells and plasma cells. The aim of this study was to characterize the antigenic targets of antibodies produced in ELS. Coronary arteries and surrounding epicardial tissue from 56 transplant recipients were collected during autopsy. Immunofluorescence was used to identify antibody-producing plasma cells. Immunoglobulin levels in tissue lysates were measured by enzyme-linked immunosorbent assay and analyzed for donor-specific HLA antibodies by Luminex assay. Cytokine and receptor expression levels were quantified using quantitative polymerase chain reaction. Plasma cells in ELS were polyclonal and produced IgG and/or IgM antibodies. In epicardial tissue, IgG (p <0.05) and IgM levels were higher in transplant patients with larger ELS than smaller ELS. In 4 of 21 (19%) patients with ELS, donor-specific HLA type II antibodies were detected locally. Cytokine and receptor expression (CXCR3, interferon γ and TGF-β) was higher in large ELS in the epicardial tissue than in other vessel wall layers, suggesting active recruitment and proliferation of T and B lymphocytes. ELS exhibited active plasma cells producing locally manufactured antibodies that, in some cases, were directed against the donor HLA, potentially mediating rejection with major consequences for the graft

Donor-Specific Antibodies Are Produced Locally in Ectopic Lymphoid Structures in Cardiac Allografts

Cardiac allograft vasculopathy (CAV) is a transplant pathology, limiting graft survival after heart transplantation. CAV arteries are surrounded by ectopic lymphoid structures (ELS) containing B cells and plasma cells. The aim of this study was to characterize the antigenic targets of antibodies produced in ELS. Coronary arteries and surrounding epicardial tissue from 56 transplant recipients were collected during autopsy. Immunofluorescence was used to identify antibody-producing plasma cells. Immunoglobulin levels in tissue lysates were measured by enzyme-linked immunosorbent assay and analyzed for donor-specific HLA antibodies by Luminex assay. Cytokine and receptor expression levels were quantified using quantitative polymerase chain reaction. Plasma cells in ELS were polyclonal and produced IgG and/or IgM antibodies. In epicardial tissue, IgG (p <0.05) and IgM levels were higher in transplant patients with larger ELS than smaller ELS. In 4 of 21 (19%) patients with ELS, donor-specific HLA type II antibodies were detected locally. Cytokine and receptor expression (CXCR3, interferon γ and TGF-β) was higher in large ELS in the epicardial tissue than in other vessel wall layers, suggesting active recruitment and proliferation of T and B lymphocytes. ELS exhibited active plasma cells producing locally manufactured antibodies that, in some cases, were directed against the donor HLA, potentially mediating rejection with major consequences for the graft

The composition of ectopic lymphoid structures suggests involvement of a local immune response in cardiac allograft vasculopathy

BACKGROUND: Cardiac allograft vasculopathy (CAV) is a multifactorial pathology limiting the survival of cardiac transplants. The etiology of CAV is unclear, but antibody-mediated and cellular-mediated responses have been implicated. We, and others, have observed ectopic lymphoid structures (ELS) surrounding epicardial coronary arteries with CAV. The potential contribution of these ELS to CAV has not been elucidated. METHODS: Epicardial coronary arteries were collected from 59 transplant patients at 2 centers and studied for ELS presence and composition using immunohistochemistry. The intima and ELS were isolated, and the expression of the genes involved in tertiary lymphoid organ (TLO) formation was measured by quantitative polymerase chain reaction. RESULTS: ELS presence was related to survival after transplantation (p = 0.013) and histologic composition of CAV (p <0.001). ELS contain B and T lymphocytes, macrophages, and antibody-producing (immunoglobulin [Ig] M and/or IgG) plasma cells. A sub-population of B lymphocytes appeared to be cluster of differentiation (CD)20(+)CD27(+) memory B lymphocytes. The messenger RNA expression of TLO markers (lymphotoxin-beta, and chemokine [C-C motif] ligand 19 and 21) was significantly higher in ELS than in the neointimal lesions. The ELS observed in this study exhibited some TLO markers but did not exhibit the distinct areas rich in B and T lymphocytes that are normally found in classic TLOs. CONCLUSIONS: The cellular composition of the ELS differs from the cellular infiltrate in CAV intimal lesions. The presence of memory B lymphocytes and plasma producing IgM and IgG cells suggests that ELS are related to local antibody production, potentially contributing to antibody-mediated CAV. ELS associated with coronary vessels containing CAV show features of underdeveloped TLOs; classic TLOs may not develop due to patient immunosuppression. (C) 2015 International Society for Heart and Lung Transplantation. All rights reserved