Abstract 16605: Peripheral Blood-Derived Myeloid Subtypes Are Associated With Cardiac Allograft Vasculopathy

Abstract

Introduction: The evidence for innate immunity’s role in cardiac allograft rejection does not necessarily extend to cardiac allograft vasculopathy (CAV), and predictors of CAV remain elusive. We hypothesize that circulating monocytes and their derived macrophage subtypes, as well as associated inflammatory and angiogenesis markers, correlate with CAV. Methods: 49 consecutive heart transplant recipients over 2 years post-transplant were enrolled. Peripheral blood mononuclear cells were isolated, with monocytes stained and measured by flow cytometry for classical (CD14 ++ /CD16 - ), intermediate (CD14 ++ /CD16 + ), and nonclassical (CD14 lo /CD16 ++ ) subtypes. Monocytes were cultured into macrophages, driven by M-CSF, and assayed for polarization markers CD86 and CD206. Serum concentrations of multiple factors including IL8, IL6, TNFα, angiopoietin-2, and VEGF-A were measured by immunoassay. CAV was assessed by angiogram and intravascular ultrasound (IVUS). Results: 22 patients had no significant CAV (Stanford class I-II) while 27 had significant CAV by angiogram or IVUS (class III-IV). Other than time since transplant (77±13 vs 135±12 months), baseline characteristics of the two groups were similar. There were no differences between monocyte subgroups in isolation, but when combined with derived macrophage polarization, patients with CAV tended toward lower M2 (CD206 + ) macrophage production (0.18±0.04%) than those without CAV (0.35±0.11%). The CAV monocyte/macrophage profile was distinct from that of a reference native CAD population. IL8 was higher late post-transplant (>7.5 years) compared to early post-transplant (1.8±0.3 vs 1.0±0.1 pg/ml). There was also higher expression of angiopoietin-2 with time after transplant and with CAV. Conclusions: The reduced ability of CAV patients to generate regulatory M2 macrophages and their higher circulating IL8 and angiopoietin-2, both linked to inflammatory macrophage signatures, support a model in which pro-inflammatory myeloid phenotypes are connected to development of CAV, and notably, these circulating monocyte and macrophage subtypes differ from those of native CAD. These cell-based and paired circulating markers could be useful to differentiate high vs. low CAV risk phenotypes.