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

• Published in: Journal of autoimmunity 2019-05, Vol.99, p.81-97
• Main Authors: 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
• Format: Article
• Language: English
• Subjects: Adult; Aged; Aged, 80 and over; Arthritis, Rheumatoid - diagnosis; Arthritis, Rheumatoid - immunology; Arthritis, Rheumatoid - metabolism; Autoimmunity; Autoreactive CD8+ T cells; Biomarkers; CD8-Positive T-Lymphocytes - immunology; CD8-Positive T-Lymphocytes - metabolism; Counter-regulation; Disease Susceptibility; Female; Histocompatibility Antigens Class I - chemistry; Histocompatibility Antigens Class I - immunology; Humans; Immunomodulation; Immunophenotyping; Male; Middle Aged; Regulatory T cells; Rheumatoid arthritis; Severity of Illness Index; T-Cell Antigen Receptor Specificity; T-Lymphocytes, Regulatory - immunology; T-Lymphocytes, Regulatory - metabolism
• ISSN: 0896-8411; 1095-9157
• DOI: 10.1016/j.jaut.2019.02.001

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)-α 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-α inhibitor therapy, respectively. These data provide evidence of a previously undescribed role of such mechanisms in the progression and therapy of RA. •Autoreactive CD8+ TN or eff cells differently affect Tregs to their vantage in RA.•Autoreactive low avidity CD8+ TN cells producing TNF-α are sustained by Tregs.•Autoreactive high avidity CD8+ Teff cells resist Tregs by killing them.•These distinctive mechan