Using BrdU to track the cell division of macrophages in the gut, he found that turnover of monocytes (which give rise to short-lived lamina propria and interstitial macrophages, CD163+CD206-) was associated with progression to AIDS, while the long-lived macrophages (submucosal and alveolar, CD163+CD206+) contributed to reservoir persistence and chronic inflammation. Here, CD163 is linked to AIDS.