FIGURE 1.

Schematic of donor-vs recipient-derived macrophages after lung and heart transplant. Lung donor-derived macrophages consist of donor alveolar and donor interstitial macrophages. Circulating monocytes can infiltrate the lung and differentiate into macrophages, including recipient monocyte-derived alveolar macrophages and recipient monocyte-derived interstitial macrophages. Similarly, after cardiac transplant, the heart consists of donor CCR2⁺ macrophages, donor CCR2⁻ macrophages, in addition to recipient monocyte-derived macrophages. Some of these recipient monocyte-derived macrophages are CCR2⁺