CD4+CD25+ regulatory T cells down-regulate co-stimulatory molecules on antigen-presenting cells

Area of Science:

• Immunology
• Cellular and Molecular Immunology

Background:

• CD4+CD25+ T cells are known to inhibit organ-specific autoimmune diseases.
• Depletion of these regulatory T cells leads to the development of autoimmune conditions.
• These cells suppress IL-2 production and proliferation of CD4+CD25- T cells in vitro.

Purpose of the Study:

• To investigate the in vitro function of CD4+CD25+ T cells, focusing on their interactions with antigen-presenting cells (APCs).
• To elucidate the mechanisms by which regulatory T cells modulate APC function.

Main Methods:

• In vitro co-culture experiments involving CD4+CD25+ T cells, CD4+CD25- T cells, and APCs.
• Analysis of co-stimulatory molecule expression (CD80, CD86) on dendritic cells.
• Measurement of mRNA levels for CD80 and CD86.

Main Results:

• CD4+CD25+ T cells down-regulated the expression of CD80 and CD86 on dendritic cells.
• Steady-state CD80 mRNA levels were decreased, but CD86 mRNA levels were not, indicating distinct regulatory mechanisms.
• This down-regulation occurred even when APCs were stimulated to increase CD80/CD86 expression.

Conclusions:

• Down-regulation of co-stimulatory molecules (CD80, CD86) on APCs is a novel effector function of CD4+CD25+ regulatory T cells.
• This mechanism contributes to the immune suppressive activity of regulatory T cells.
• Distinct pathways regulate CD80 and CD86 expression in response to regulatory T cell interaction.