Conclusion
Our research provides insight into the immunological processes that may lead to the fibrotic changes noted in the lungs following COVID-19.
Methods
A total of 48 BAL samples were collected over three intervals (1, 3, and 6 months) and underwent cytology, gene, and protein expression analyses for pro/anti-inflammatory lung cytokines and chemokines using reverse transcription polymerase chain reaction and enzyme-linked immunosorbent assay.
Results
One month after infection, there were significant increases in the levels of IL-6 and IL-8. These levels decreased gradually over the course of 6 months but were still higher than those seen in control. Interferon-gamma and tumor necrosis factor alpha exhibited similar patterns. Persistent elevations were found in IL-10, IL-13, and pro-fibrotic M2 macrophages' chemokines (CCL13 and CCL18) for 6 months. Furthermore, pronounced neutrophilia was observed at 1 month post-COVID, highlighting persistent inflammation and lung damage. Neutrophil efferocytosis, aiding inflammation resolution and tissue repair, was evident at the 1-month time interval. A notable time-dependent reduction in CD28 was also noticed.