Figure 2.

The role of Macrophages in secondary infection and trained immunity. After a mild infection caused by a specific pathogen such as adenoviruse, TR-AMs upregulate MHC II expression in response to CD8+ T lymphocytes and are rapidly activated in secondary infections (81). Mo-AMs that persists in the alveolar cavity after primary infection are also more likely to be activated and form part of trained AMs. After recovery from severe infections, TR-AMs are paralyzed with reduced phagocytosis and are more susceptible to secondary infections.