# Direct contact with natural killer cells reprograms monocyte-derived dendritic cells into a tolerogenic phenotype

## TL;DR

Contact with natural killer cells changes monocyte-derived dendritic cells into a form that reduces inflammation and promotes immune tolerance.

## Contribution

The study identifies a novel approach to reprogram dendritic cells into a tolerogenic phenotype using natural killer cell interactions and confirms key transcription factors involved.

## Key findings

- Dendritic cells exposed to natural killer cells show reduced T-cell activation and increased regulatory mediators like IL-10 and IDO1.
- CRISPR knockout experiments reveal that transcription factors IKZF1 and PU.1 are essential for the tolerogenic reprogramming of dendritic cells.
- The study confirms that tolerogenic dendritic cells have decreased levels of co-stimulatory markers such as CD11c, CD40, and CD44.

## Abstract

Tissue-infiltrating monocyte-derived dendritic cells (DCs) and macrophages are key antigen-presenting cells promoting inflammation and tissue damage by releasing proinflammatory cytokines and strongly activating T cells. These antigen-presenting cells are prominent in inflamed tissues, including in conditions such as inflammatory bowel disease. Modulating the number or function of these cells presents an opportunity to mitigate inflammation and promote immune tolerance in inflammatory disorders. In this study, we comprehensively evaluate a novel approach to modulate these cell populations. First, we employ an antibody-mediated approach to selectively deplete inflammatory DCs while simultaneously reprogramming surviving cells toward a tolerogenic phenotype. Second, we utilize a natural killer–DC co-culture system to dissect molecular mechanisms of DC tolerance induction through integrated transcriptomic and epigenomic analysis, complemented by functional assays. We confirm that the generated DCs exhibit tolerogenic properties, marked by a reduced ability to induce allogenic T-cell activation, increased expression of regulatory mediators including IL-10 and IDO1, and decreased levels of co-stimulatory and activation markers such as CD11c, CD40, and CD44. Finally, using CRISPR knockout, we confirm the essential role of transcription factors IKZF1 and PU.1 in this process. Our findings advance the understanding of how epigenetic remodeling and transcription factor activity govern DC tolerance, and highlight promising therapeutic avenues for DC-targeted therapeutic approaches in inflammatory disorders.