Trained immunity

Trained immunity is the idea that your innate immune cells can 'learn'. The concept comes mainly from Mihai Netea and colleagues. It means your fast-response immune cells (mainly monocytes, macrophages, and NK cells) can mount a stronger, non-specific reaction to a later threat, after an initial 'training' event. And they do this without the classic memory of the adaptive immune system. How? The training reprograms the cells in two ways. It changes the epigenetic marks (histone tags) on inflammatory genes. And it rewires their metabolism toward fast sugar-burning (aerobic glycolysis). Together these lower the cell's activation threshold for weeks to months. The best-known triggers are β-glucan (a fungal cell-wall component) and the BCG tuberculosis vaccine. In some controlled trials, both reduced unrelated infections and even all-cause death. This is different from the B- and T-cell memory built by mutation and selection. It is an epigenetic memory in the innate side of immunity.

Last reviewed: June 22, 2026

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