For the optimal management of RA individuals, clinicians need to consider both the risk of disease relapse and that of a decreased vaccine immunogenicity. spike peptides. FACS analysis was performed to identify the cells responding to spike activation. RA disease activity was evaluated by clinical exam through the DAS28crp, and local and/or systemic medical adverse events were authorized. In RA individuals, the ongoing restorative regimen was revised during the vaccination period according to the American College of Rheumatology indications. Results We prospectively enrolled 167 HCWs and 35 RA individuals. Anti-RBD-antibodies were detected in almost all individuals (34/35, 97%), even though titer was significantly reduced in individuals under CTLA-4-inhibitors (median: 465 BAU/mL, IQR: 103-1189, p 0.001) or IL-6-inhibitors (median: 492 BAU/mL, IQR: 161-1007, p 0.001) compared to HCWs (median: 2351 BAU/mL, IQR: 1389-3748). T-cell-specific response obtained positive in most of RA individuals [24/35, (69%)] with significantly lower IFN- levels in individuals under biological therapy such as IL-6-inhibitors (median: 33.2 pg/mL, IQR: 6.1-73.9, p 0.001), CTLA-4-inhibitors (median: 10.9 pg/mL, IQR: 3.7-36.7, p 0.001), and TNF–inhibitors (median: 89.6 pg/mL, IQR: 17.8-224, p=0.002) compared to HCWs (median: 343 pg/mL, IQR: 188-756). A significant correlation between the anti-RBD-antibody titer and spike-IFN–specific T-cell response was found in RA individuals (rho=0.432, p=0.009). IFN- T-cell response was mediated by CD4+ and CD8+ T cells. Finally, no significant increase in disease activity was found in RA individuals following vaccination. Summary This study showed for the first time that antibody-specific and whole-blood spike-specific T-cell reactions induced from the COVID-19 mRNA-vaccine were present in the majority of RA individuals, who underwent a strategy of temporary suspension of immunosuppressive treatment during vaccine administration. However, the magnitude of specific reactions was (R)-Bicalutamide dependent on the immunosuppressive therapy given. In RA individuals, BNT162b2 vaccine was safe and disease activity remained stable. Activation PBMCs, isolated from HCWs (n=7) and RA individuals (n=15), were thawed, counted, assessed for viability, and rested for 2-4 hours at 37C in RPMI supplemented with 1% L-glutamine, 1% penicillin/streptomycin (Euroclone S.p.A, Italy), and 10% heat-inactivated FBS. For antigen-specific T-cell activation, PBMCs were seeded at a concentration of 2.5 106 cells/mL in a final volume of 200 L inside a 96-multiwell flat-bottom plate (COSTAR, Sigma Aldrich), and stimulated with spike peptide pool at 1 g/mL or Staphylococcal Enterotoxin B (SEB) at 200 ng/mL, used like a positive control. We added anti-CD28 and anti-CD49d monoclonal antibodies (BD Biosciences San Jose, USA) to co-stimulate cells at a final concentration of 1 1 g/mL each. After 1h of incubation at 37C (5% CO2), a Golgi plug (BD Biosciences) at 1 L/mL was added to cell cultures to inhibit cytokine secretion and to allow intracellular molecule detection by circulation cytometry. After 16-24?h, cells were stained while described in the following. T-Cell Subpopulations and Intracellular IFN- Detection Stimulated PBMCs were stained with fluorochrome-conjugated antibodies prepared in Amazing Stain Buffer (BD Biosciences) (observe Supplementary Number S1 for gating strategy). The Cytofix/Cytoperm remedy kit (BD Biosciences) was utilized for the intracellular IFN- staining, according to the manufacturers instructions (observe Supplementary Table S1 for the list of antibodies and reagents used). Dead cells were excluded from your analysis (R)-Bicalutamide by COL4A3 part/ahead scatter gating and then by Fixable Viability stain (R)-Bicalutamide 700 (BD Biosciences). At least 100,000 lymphocytes from each sample were gated (except for three samples, two from your unstimulated conditions and one from your SEB condition which were gated with 80,000 events). Samples were acquired on a BD Lyric (BD Biosciences) cytometer and data were analyzed from the FlowJo software (version 10, Tree Celebrity). IFN–mediated T-cell response was regarded as positive when: i) the rate of recurrence of the SARS-COV-2 peptide-stimulated PBMCs was at least twofold higher compared to the unstimulated control; and ii) at least 10 events were present within the IFN- gate (18). Anti-SARS-CoV-2 Specific IgG Evaluation The humoral response to vaccination was assessed by quantifying the anti-Nucleoprotein-IgG and the anti-RBD-IgG (Architect? i2000sr Abbott Diagnostics, Chicago, IL). Anti-N-IgG were indicated as arbitrary devices.