Chemokine receptor expression by inflammatory T cells in EAE

Area of Science:

• Immunology
• Neuroscience
• Cell Biology

Background:

• Chemokines and their receptors are crucial for immune cell trafficking to tissues.
• Multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), involve T cell infiltration into the central nervous system (CNS).
• The chemokine receptor CCR6 is reportedly expressed by T helper 17 (Th17) cells, implicated in MS and EAE pathogenesis.

Purpose of the Study:

• To investigate whether CCR6 expression specifically identifies distinct inflammatory T cell subsets within the CNS during EAE.
• To analyze the expression of chemokine receptors CCR6 and CXCR3 in relation to cytokine production (IFNγ and IL-17) by CD4+ and CD8+ T cells in the CNS during EAE.

Main Methods:

• Induction of EAE in mice and subsequent analysis of CNS-infiltrating T cells at peak disease.
• Flow cytometry to assess cytokine production (IFNγ, IL-17) and chemokine receptor expression (CCR6, CXCR3) on CD4+ and CD8+ T cells.
• Real-time PCR to detect mRNA expression of IFNγ, IL-17A, T-bet, and RORγt.
• Double immunofluorescence staining to confirm co-localization of CCR6 and CD4 in spinal cord infiltrates.

Main Results:

• CCR6 was expressed by Th1, Th1+17, and Th17 CD4+ T cells, not exclusively by Th17 cells.
• CD8+ T cells expressed CXCR3 but not CCR6; they produced IFNγ but not IL-17A.
• CXCR3 was expressed by both CD4+ and CD8+ T cells, irrespective of their cytokine profile.
• Both CCR6+ and CXCR3+ CD4+ T cells expressed mRNA for IFNγ, IL-17A, T-bet, and RORγt.
• CD4-negative CCR6+ cells, including macrophages/microglia, were also identified.

Conclusions:

• CCR6 and CXCR3 do not serve as exclusive markers for specific CD4+ T cell subsets in EAE.
• Th1 and mixed Th1+17 CD4+ T cell populations are predominant in the CNS during EAE.
• The findings challenge the selective role of CCR6 in identifying Th17 cells in the context of EAE pathogenesis.