# Erythroblasts Promote the Development of a Suppressive Lymphocyte Phenotype via Treg Induction and PD1 Upregulation on the Surfaces of B-Cells: A Study on the Subpopulation-Specific Features of Erythroblasts

## TL;DR

Erythroblasts influence immune cells by promoting regulatory T cells and increasing PD-1 on B cells, with effects depending on their subpopulation.

## Contribution

The study reveals subpopulation-specific immunoregulatory roles of erythroblasts through Treg induction and PD-1 upregulation.

## Key findings

- Erythroblast-conditioned media promotes Treg development and increases PD-1 on B cells.
- CD45+ erythroblasts upregulate PDL1 and Galectin-9 under hemolytic stress.
- CD45- erythroblasts primarily increase TGFb production.

## Abstract

This study identifies the novel effects of soluble factors derived from murine erythroblasts on lymphoid cell phenotypes. These effects were observed following the treatment of splenic mononuclear cells with erythroblast-conditioned media received from both healthy mice and mice subjected to hematopoiesis-activating conditions (hypoxia, blood loss, and hemolytic anemia), suggesting a common mechanism of action. Using flow cytometry, we elucidated that erythroblast-derived soluble products modulate T cell differentiation by promoting Treg development and increasing PD-1 surface expression on B cells. The immunoregulatory potential of erythroblasts is subpopulation-dependent: CD45+ erythroblasts respond to hemolytic stress by upregulating the surface expression of immunosuppressive molecules PDL1 and Galectin-9, while CD45- erythroblasts primarily increase TGFb production. These findings highlight the regulatory role of erythroblasts in modulating immune responses.