Impaired epidermal Langerhans cell maturation in TGFβ-inducible early gene 1 (TIEG1) knockout mice

Retinoblastoma cell-derived Twist protein promotes regulatory T cell development

BACKGROUND

The development of tumor tissue-infiltrating regulatory T cell (Treg) is incompletely understood. This study investigates the role of retinoblastoma cell (Rbc)-derived Twist‑related protein 1 (Twist) in the Treg development.

METHODS

The surgically removed Rb tissues were collected. Rbcs were cultured with CD4⁺ T cells to assess the role of Rbc-derived Twist in the Treg generation.

RESULTS

We found that more than 90% Rbcs expressed Twist. Foxp3⁺ Tregs were detected in the Rb tissues that were positively correlated with the Twist expression in Rbcs, negatively associated with Rb patient survival and sight survival. Treating Rbcs with hypoxia promoted the Twist expression that could be detected in the cytoplasm, nuclei and on the cell surface. Twist activated CD4⁺ T cells by binding the TLR4/myeloid differentiation factor 2 complex and promoted the transforming growth factor-β-inducible early gene 1 product and Foxp3 expression. These Rbc-induced Foxp3⁺ Tregs showed immune-suppressive function on CD8⁺ T cell proliferation.

CONCLUSIONS

Rbcs express Twist, that induces IL-4⁺ Foxp3⁺ Tregs; the latter can inhibit CD8⁺ cytotoxic T cell activities. Therefore, Twist may play an important role in the pathogenesis of Rb.

Smad2/4 Signaling Pathway Is Critical for Epidermal Langerhans Cell Repopulation Under Inflammatory Condition but Not Required for Their Homeostasis at Steady State

Epidermal Langerhans cells (LCs) are skin-resident dendritic cells that are essential for the induction of skin immunity and tolerance. Transforming growth factor-β 1 (TGFβ1) is a crucial factor for LC maintenance and function. However, the underlying TGFβ1 signaling pathways remain unclear. Our previous research has shown that the TGFβ1/Smad3 signaling pathway does not impact LC homeostasis and maturation. In this study, we generated mice with conditional deletions of either individual Smad2, Smad4, or both Smad2 and Smad4 in the LC lineage or myeloid lineage, to further explore the impact of TGFβ1/Smad signaling pathways on LCs. We found that interruption of Smad2 or Smad4 individually or simultaneously in the LC lineage did not significantly impact the maintenance, maturation, antigen uptake, and migration of LCs in vivo or in vitro during steady state. However, the interruption of both Smad2 and Smad4 pathways in the myeloid lineage led to a dramatic inhibition of bone marrow-derived LCs in the inflammatory state. Overall, our data suggest that canonical TGFβ1/Smad2/4 signaling pathways are dispensable for epidermal LC homeostasis and maturation at steady state, but are critical for the long-term LC repopulation directly originating from the bone marrow in the inflammatory state.