Figure 1.

A. Classical adaptive immunological memory involves gene recombination in B- and T-lymphocytes, which confers high specificity and very often long-term, pathogen-specific protection (up to decades). B. Trained immunity defines a de-facto innate immune memory that induces enhanced inflammatory and antimicrobial properties in innate immune cells, responsible for an increased non-specific response to subsequent infections and improved survival of the host.