MMP9 and infection: In the current study, we collected sheep alveolar macrophages that had been infected with MO for 28 days and detected changes in the expression of genes potentially involved in lung tissue damage or remodelling, such as MMP9, S100A8, IL10, IRAK1, and MAP3K1. These findings further reveal the potential function of PADI2 in the macrophage response to MO infection.