Interleukin-35-Producing CD8α⁺ Dendritic Cells Acquire a Tolerogenic State and Regulate T Cell Function

Area of Science:

• Immunology
• Cell Biology
• Immunotherapy

Background:

• Dendritic cells (DCs) are crucial in regulating adaptive immunity, directing responses towards either immunity or tolerance.
• Interleukin-35 (IL-35) is a cytokine known for its immunosuppressive functions.

Purpose of the Study:

• To generate a dendritic cell (DC) line that constitutively secretes the tolerogenic cytokine IL-35.
• To investigate the effects of IL-35 secretion by DCs on T cell responses and immune tolerance both *in vitro* and *in vivo*.

Main Methods:

• Generation of a CD8α+ DC line engineered to constitutively secrete IL-35.
• Assessment of T cell proliferation and function upon co-culture with IL-35-secreting DCs.
• Analysis of DC phenotype, including surface marker expression (CD11b, MHC class II) and cytokine production (IL-10).
• Evaluation of vaccination with IL-35-expressing DCs in mouse models of tumor growth and experimental autoimmune encephalitis (EAE).

Main Results:

• Constitutive IL-35 secretion by DCs impaired CD4+ and CD8+ T lymphocyte proliferation and function *in vitro* and *in vivo*.
• IL-35 induced a tolerogenic phenotype in DCs, characterized by altered CD11b and MHC class II expression, reduced costimulatory potential, and increased IL-10 production.
• Vaccination with IL-35-expressing DCs promoted tumor growth in mice.
• IL-35-expressing DCs significantly reduced the severity of experimental autoimmune encephalitis (EAE), with greater efficacy when antigen-pulsed.

Conclusions:

• IL-35-secreting DCs can induce immune tolerance through an indirect mechanism involving antigen-presenting cells.
• Engineered IL-35-expressing DCs represent a potential therapeutic strategy for autoimmune diseases.