Zbtb20 expression defines a functionally distinct Treg subset that is essential for intestinal homeostasis
Creators: name: Krzyzanowska, Agata K.
Publisher: name: No Publisher Supplied
Year: 2023

description: Members of the BTB-Zinc Finger (BTB-ZF) family are essential, non-redundant transcription factors that control the development and function of lymphocytes. Screening for potential new lineage-defining BTB-ZF genes identified a distinct subset of T cells that expressed Zbtb20. Approximately half of the Zbtb20-expressing T cells also expressed FoxP3, the lineage-defining transcription factor for regulatory T cells (Tregs). Zbtb20-expressing Tregs were phenotypically and genetically distinct from the larger conventional Treg population. Of interest, these cells expressed "pre-formed" IL-10 mRNA which correlated with their ability to rapidly secrete a large quantity of the cytokine immediately upon primary stimulation. These characteristics were found in antigen unexperienced Zbtb20-expressing T cells in the thymus, indicating that this effector function is programmed during their development. Although Zbtb20+ Tregs could be found in the thymus and spleen, they were enriched in the intestine and expanded during DSS-induced colitis. The deletion of Zbtb20 in T cells impaired their ability to secrete IL-10 that resulted in intestinal epithelial layer damage causing loss of barrier function. Consequently, Zbtb20-cKO mice developed severe DSS-induced colitis and often died due to the disease. Importantly, adoptive transfer of Zbtb20-expressing Tregs was sufficient to rescue the mice from death, whereas Tregs depleted of Zbtb20-expressing cells or with a conditional deletion of Zbtb20 were not. Zbtb20-expressing T cells constitutively expressed IL-10 suggesting crosstalk with other cell types. Consistent with this, in the absence of Zbtb20 in T cells, high levels of myeloid cell-associated cytokines (IL-6 and IL-1) were detected in serum as well as increased accumulation of pro-inflammatory macrophages in the colons of these mice during colitis. Moreover, activation of macrophages with anti-CD40 treatment induced substantial weight loss in Zbtb20-cKO mice indicating that in the absence of Zbtb20 in T cells, normal intestinal macrophage responses were disrupted. Thus, Zbtb20-expressing Tregs regulate gut homeostasis by acting on intestinal myeloid cells.Unlike a lot of intestinal Tregs that are induced in situ after antigen stimulation, Zbtb20-expressing Tregs develop in the thymus. Zbtb20 was detected in CD24hi, double-positive, and CD62Llo CD4 single-positive thymocytes, indicating that expression of the transcription factor and the phenotype of these cells were thymic-induced during their development. Moreover, Zbtb20 expression was not induced in “conventional” Tregs by activation in vitro or in vivo. Collectively, our data show that the expression of a specific member of the BTB-ZF family identifies and controls the function of a unique subset of Tregs that are essential for the health of the intestine. Zbtb20-expressing Tregs have potent immunosuppressive abilities and rather than acutely producing IL-10 in response to antigen, maintain intestinal homeostasis through continuous secretion of IL-10. Thus, our data indicate that some "naïve" Tregs have innate effector functions that are not acquired upon differentiation in the periphery.