# Assessment and Characterization of Induced Alloantigen-Specific Regulatory T Cells Obtained by the Inhibition of CDK8/19 with the AS2863619 Compound

## TL;DR

This study shows that using a CDK8/19 inhibitor can convert T cells into regulatory T cells that help with immune tolerance, which could be useful for transplants.

## Contribution

The study introduces a novel method to generate alloantigen-specific Tregs using the CDK8/19 inhibitor AS2863619.

## Key findings

- AS2863619 with IL-2 promotes transdifferentiation into functional ag-Tregs.
- Generated Tregs show tolerogenic activity and migration properties in the spleen.
- These Tregs regulate immune homeostasis and naïve T cell affinity to alloantigens.

## Abstract

Foxp3+ regulatory T (Treg) cells play a pivotal role in inducing immune tolerance. The expression of Foxp3 in Treg cells depends on the stability of transcription factors that are directly linked to the molecular interplay between Stat5a and cyclin-dependent kinase CDK8/19. In this study, dendritic cells obtained from C57BL/6 male mice were co-cultured with CD4+ splenocytes obtained from Balb/c male mice to obtain alloantigen-specific CD4+ T cells. Next, these alloantigen-specific CD4+ T cells were cultured with the addition of the CDK8/19 inhibitor AS2863619 compound, TGF-β1, and IL-2 to induce their transdifferentiation into alloantigen-specific CD4+ Foxp3+ Treg cells. The efficacy of this cocktail in promoting the transdifferentiation of activated CD4+ lymphocytes into alloantigen-specific Treg cells (ag-Tregs) was further evaluated using Nanostring gene expression profiling, flow cytometry, ELISA, and in vivo migration assays. The results showed that the addition of the AS2863619 compound along with IL-2 generated effector memory ag-Tregs exhibiting tolerogenic activity, migration properties, and mechanisms for regulating immune homeostasis in the spleen. In conclusion, these findings suggest that the AS2863619-derived effector memory Tregs possess functional properties that support immune tolerance and regulate homeostasis in the spleen, thereby regulating the affinity of naïve T cells to alloantigens, highlighting their potential relevance in transplantology.