CCL2 and infection: Figure 3E demonstrates that intratracheal instillation of MCMV led to a notable alteration in cytokine release in the BAL fluid. However, three days after infection, intravenous administration of mMSC-exos significantly reduced the levels of pro-inflammatory cytokines and chemokines, including TNF-α, IL-1β, and MCP-1, in the BAL fluid compared to treatment with MCMV and the 3T3-exo group. Additionally, mMSC-exos increased the secretion of the anti-inflammatory cytokine IL-10 in the BAL fluid (Figure 3E).