Visualising the interaction of CD4 T cells and DCs in the evolution of inflammatory arthritis.

Objectives: Successful early intervention in rheumatoid arthritis (RA) with the aim of resetting immunological tolerance requires a clearer understanding of how specificity, cellular kinetics and spatial behaviour shape the evolution of articular T cell responses. We aimed to define initial seeding of articular CD4 ⁺ T cell responses in early experimental arthritis, evaluating their dynamic behaviour and interactions with dendritic cells (DCs) in the inflamed articular environment.
Methods: Antigen-induced arthritis was used to model articular inflammation. Flow cytometry and PCR of T cell receptor (TCR) diversity genes allowed phenotypic analysis of infiltrating T cells. The dynamic interactions of T cells with joint residing DCs were visualised using intravital multiphoton microscopy.
Results: Initial recruitment of antigen-specific T cells into the joint was paralleled by accumulation of CD4 ⁺ T cells with diverse antigen-receptor expression and ability to produce tumour necrosis factor alpha (TNFα) and interferon gamma (IFNγ) on mitogenic restimulation. A proportion of this infiltrate demonstrated slower motility speeds and engaged for longer periods with articular DCs in vivo. Abatacept treatment did not disrupt these interactions but did reduce T cell expression of inducible costimulatory (ICOS) molecule. We also demonstrated that non-specific CD4 ⁺ T cells could be recruited during these early articular events.
Conclusions: We demonstrate that CD4 ⁺ T cells engage with articular DCs supporting antigen specific T cell reactivation. This cellular dialogue can be targeted therapeutically to reduce local T cell activation.
Competing Interests: Competing interests: None declared.
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