Counter-regulation of regulatory T cells by autoreactive CD8+ T cells in rheumatoid arthritis

01 Pubblicazione su rivista
Cammarata Ilenia, Martire Carmela, Citro Alessandra, Raimondo Domenico, Fruci Doriana, Melaiu Ombretta, D', Oria Valentina, Carone Chiara, Peruzzi Giovanna, Cerboni Cristina, Santoni Angela, Sidney John, Sette Alessandro, Paroli Marino, Caccavale Rosalba, Milanetti Edoardo, Riminucci Mara, Timperi Eleonora, Piconese Silvia, Manzo Antonio, Montecucco Carlomaurizio, Scrivo Rossana, Valesini Guido, Cariani Elisabetta, Barnaba Vincenzo
ISSN: 0896-8411

The mechanisms whereby autoreactive T cells escape peripheral tolerance establishing thus autoimmune diseases in humans remain an unresolved question. Here, we demonstrate that autoreactive polyfunctional CD8+ T cells recognizing self-antigens (i.e., vimentin, actin cytoplasmic 1, or non-muscle myosin heavy chain 9 epitopes) with high avidity, counter-regulate Tregs by killing them, in a consistent percentage of rheumatoid arthritis (RA) patients. Indeed, these CD8+ T cells express a phenotype and gene profile of effector (eff) cells and, upon antigen-specific activation, kill Tregs indirectly in an NKG2D-dependent bystander fashion in vitro. This data provides a mechanistic basis for the finding showing that AE-specific (CD107a+) CD8+ T killer cells correlate, directly with the disease activity score, and inversely with the percentage of activated Tregs, in both steady state and follow-up studies in vivo. In addition, multiplex immunofluorescence imaging analyses of inflamed synovial tissues in vivo show that a remarkable number of CD8+ T cells express granzyme-B and selectively contact FOXP3+ Tregs, some of which are in an apoptotic state, validating hence the possibility that CD8+ Teff cells can counteract neighboring Tregs within inflamed tissues, by killing them. Alternatively, the disease activity score of a different subset of patients is correlated with the expansion of a peculiar subpopulation of autoreactive low avidity, partially-activated (pa)CD8+ T cells that, despite they conserve the conventional naïve (N) phenotype, produce high levels of tumor necrosis factor (TNF)-? and exhibit a gene expression signature of a progressive activation state. Tregs directly correlate with the expansion of this autoreactive (low avidity) paCD8+ TN cell subset in vivo, and efficiently control their differentiation rather their proliferation in vitro. Interestingly, autoreactive high avidity CD8+ Teff cells or low avidity paCD8+ TN cells are significantly expanded in RA patients who would become non-responders or patients who would become responders to TNF-? inhibitor therapy, respectively. These data provide evidence of a previously undescribed role of such mechanisms in the progression and therapy of RA.

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