Delicate and dynamic immunological equilibrium

Immune cells patrolling the microbe-rich intestine are able to ‘tolerate’ harmless, microorganisms while attacking and eliminating potentially dangerous pathogens. Work published online this week in Nature Immunology deepens our understanding of how this process occurs.

Previous work implicates immune cells called regulatory T cells in enforcing immunological tolerance to harmless or ‘commensal’ gut microbes. Bali Pulendran and colleagues pinpointed particular populations of gut ‘accessory’ cells called macrophages and dendritic cells which, although located adjacent to each other in the gut mucosa, exert opposite immune functions. Macrophages promote production of regulatory T cells, whereas dendritic cells elicit development of potentially pathogenic non-regulatory T cells capable of releasing pro-inflammatory mediators.

Complete understanding of the molecular mechanisms regulating this likely dynamic cooperation among accessory cell populations in the gut awaits further investigation.