Key role for IL-21 in experimental autoimmune uveitis

Area of Science:

• Immunology
• Neuroimmunology
• Cytokine biology

Background:

• Interleukin-21 (IL-21) is a type 1 cytokine sharing the common cytokine receptor gamma chain (γc) with other interleukins.
• IL-21 promotes Th17 cell differentiation and is linked to autoimmune diseases, but its role in CNS autoimmune disorders is debated.
• IL-2 and IL-21, though homologous, have distinct functions; IL-2 supports regulatory T cells, while IL-21 is associated with autoimmunity.

Purpose of the Study:

• To investigate the role of IL-21 in the pathogenesis of experimental autoimmune uveitis (EAU), a model for CNS autoimmune disease.
• To determine if T cells coexpressing IL-2 and IL-21 are involved in EAU development.
• To evaluate the therapeutic potential of targeting the IL-21 pathway in CNS autoimmunity.

Main Methods:

• Generation of dual-reporter transgenic mice (Il21-mCherry/Il2-emGFP) to track IL-21 and IL-2 expression in T cells.
• Induction of experimental autoimmune uveitis (EAU) in wild-type and Il21 receptor knockout (Il21r(-/-)) mice.
• Adoptive transfer experiments using T cells from Il21r(-/-) mice to assess their impact on EAU severity.

Main Results:

• Development of EAU correlated with the presence of T cells coexpressing IL-21 and IL-2 in the retina.
• Il21r(-/-) mice exhibited increased resistance to EAU development compared to wild-type controls.
• Adoptive transfer of Il21r(-/-) T cells resulted in significantly reduced EAU severity, highlighting IL-21's critical role.

Conclusions:

• IL-21 is essential for the development of experimental autoimmune uveitis.
• The presence of IL-21-producing T cells in the retina is associated with disease pathogenesis.
• Targeting IL-21/γc signaling pathways presents a potential therapeutic strategy for managing CNS autoimmune diseases like uveitis.