IdeS reduced or eliminated donor-specific antibodies and permitted HLA-incompatible transplantation in 24 of 25 patients. (Funded by Hansa Medical; ClinicalTrials.gov numbers, NCT02224820 , NCT02426684 , and NCT02475551 .).

No abstract

Ligation of class I molecules by anti-HLA Ab stimulates an intracellular signaling cascade resulting in endothelial cell (EC) survival and proliferation, and has been implicated in the process of chronic allograft rejection and transplant-associated vasculopathy. In this study, we used small interfering RNA blockade of focal adhesion kinase (FAK) protein to determine its role in class I-mediated organization of the actin cytoskeleton, cell survival, and cell proliferation in primary cultures of human aortic EC. Knockdown of FAK appreciably inhibited class I-mediated phosphorylation of Src at Tyr418, p85 PI3K, and Akt at both Thr308 and Ser473 sites. FAK knockdown also reduced class I-mediated phosphorylation of paxillin at Try118 and blocked class I-induced paxillin assembly into focal contacts. FAK small interfering RNA completely abrogated class I-mediated formation of actin stress fibers. Interestingly, FAK knockdown did not modify fibroblast growth factor receptor expression induced by class I ligation. However, FAK knockdown blocked HLA class I-stimulated cell cycle proliferation in the presence and absence of basic fibroblast growth factor. This study shows that FAK plays a critical role in class I-induced cell proliferation, cell survival, and focal adhesion assembly in EC and may promote the development of transplant-associated vasculopathy.

Among transplant recipients, those who produce antibodies against the donor's human leukocyte antigens (HLAs) are at higher risk for antibody-mediated rejection and transplant vasculopathy, which is a progressive, vasculo-occlusive disease that results in ischemic injury and deterioration of organ function. Antibodies against HLA class I (HLA-I) molecules are thought to contribute to transplant vasculopathy by triggering signals that elicit the activation and proliferation of endothelial cells. Here, we demonstrate a molecular association between HLA-I and the integrin β4 subunit after the stimulation of endothelial cells with HLA-I–specific antibodies. Knockdown of integrin β4 in these cells abrogated the ability of HLA-I to stimulate the phosphorylation of the kinases Akt, extracellular signal–regulated kinase (ERK), and Src, as well as cellular proliferation. Similarly, reducing the abundance of HLA-I suppressed integrin β4–mediated phosphorylation of ERK and the migration of endothelial cells on laminin-5, a component of the extracellular matrix. These results indicate a mutual dependency between HLA-I and the integrin β4 subunit to stimulate the proliferation and migration of endothelial cells, which may be important in promoting transplant vasculopathy and tumor angiogenesis.

Chronic rejection manifests as transplant vasculopathy which is characterized by intimal thickening of the vessels of the allograft. Intimal thickening is thought to result from the migration and proliferation of vascular smooth muscle cells (SMC) in the vessel media followed by deposition of extracellular matrix proteins. The development of post-transplant anti-HLA antibodies (Ab) is strongly correlated with the development of transplant vasculopathy and graft loss. Here we demonstrate that crosslinking of HLA class I molecules on the surface of human SMC with anti-HLA class I Ab-induced cell proliferation and migration. Class I ligation also increased phosphorylation of Focal Adhesion Kinase (FAK), Akt and ERK1/2 in SMC. Knockdown of FAK by siRNA attenuated class I-induced phosphorylation of Akt and ERK1/2, as well as cell proliferation and migration. These results indicate that ligation of HLA class I molecules induces SMC migration and proliferation in a FAK dependent manner, which may be important in promoting transplant vasculopathy.