Pathogen-specific CD8 T cell responses are directly inhibited by IL-10.

Area of Science:

• Immunology
• Cellular Biology
• Infectious Diseases

Background:

• CD8 T cell regulation is crucial for fighting intracellular pathogens.
• Interleukin-10 (IL-10) is a cytokine that can inhibit T cell responses and antigen-presenting cell (APC) functions.
• The direct impact of IL-10 on T cell activation and proliferation in vivo remains unclear.

Purpose of the Study:

• To investigate the role of IL-10 in regulating CD8 T cell expansion and contraction during Listeria monocytogenes infection.
• To determine whether IL-10 directly affects CD8 T cells or APCs.
• To understand the mechanism by which IL-10 modulates immune responses and memory T cell formation.

Main Methods:

• Studied CD8 T cell responses in mice lacking IL-10 or IL-10 receptor subunit 2 (IL-10R2) following L. monocytogenes infection.
• Analyzed surface expression of IL-10R on activated CD8 T cells.
• Compared T cell expansion and proliferation in wild-type versus knockout mice.

Main Results:

• Absence of IL-10 enhanced both primary and memory CD8 T cell responses to L. monocytogenes.
• IL-10 receptor (IL-10R) was transiently upregulated on activated CD8 T cells.
• CD8 T cells lacking IL-10R2 showed increased expansion, while APCs lacking IL-10R2 did not affect T cell responses.

Conclusions:

• IL-10 directly limits the expansion of pathogen-specific CD8 T cells during bacterial infection.
• IL-10 acts extrinsically on CD8 T cells, rather than APCs, to regulate immune response magnitude.
• This mechanism is important for modulating the size of memory CD8 T cell populations.