The Case for an Expanded Concept of Trained Immunity

Area of Science:

• Immunology
• Cell Biology

Background:

• Trained immunity, a form of innate immune memory, was initially linked to hematopoietic cells like monocytes, macrophages, and NK cells.
• Chronic inflammatory diseases, such as vulvovaginal candidiasis caused by *Candida albicans*, present complex challenges in understanding immune responses.

Purpose of the Study:

• To review existing data supporting the concept of trained immunity.
• To explore unanswered questions regarding trained immunity in the context of *Candida albicans* infections.
• To propose an expanded definition of trained immunity encompassing diverse cell lineages.

Main Methods:

• Discussion of historical and recent scientific data.
• Analysis of cellular memory mechanisms in various cell types.
• Conceptual expansion of the trained immunity paradigm.

Main Results:

• Evidence supports the original concept of trained immunity in hematopoietic cells.
• Epithelial cells and other mammalian cells demonstrate memory capabilities after stimulation.
• Microbial encounters can induce memory in a wide range of cell types beyond the immune system.

Conclusions:

• The concept of trained immunity should be broadened to include memory acquisition in all cell lineages.
• This expanded view better reflects the complexity of innate immunity.
• A comprehensive understanding of trained immunity is crucial for addressing infectious and inflammatory diseases.