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Our objective was to evaluate the immunogenicity of branded and biosimilar infliximab by detecting changes in T-helper-9 (Th9) percentages induced by an in vitro stimulation test., Methods: Peripheral blood mononuclear cells collected from 55 consecutive rheumatoid arthritis (RA) outpatients (15 drug free, 20 successfully treated with branded infliximab, 20 branded infliximab inadequate responders) and 10 healthy controls were cultured, with or without 50 μg/mL of infliximab originator (Remicade ® ) or 50 μg/mL of infliximab biosimilar (Remsima ® ) for 18 h. Th9 lymphocytes were identified by means of flow cytometry as PU.1 and IRF4-expressing, IL-9-secreting CD4⁺ T cells. Furthermore, the markers CCR7 and CD45RA were used to distinguish naïve from memory IL-9 producer cells., Results: Under unstimulated conditions, the drug-free RA patients had the highest percentages of Th9 lymphocytes. Following stimulation with branded infliximab, the percentages of PU.1 and IRF4-expressing Th9 cells, CCR7⁺, CD45RA - (central memory) and CCR7 - , CD45RA - (effector memory) cells significantly increased in the group of inadequate responders, but no significant variation was observed after exposure to the biosimilar of infliximab., Conclusions: Th9 cells seem to be involved in the immune response to the epitopes of branded, but not biosimilar, infliximab, and this may depend on the recall and stimulation of both central and effector memory cells., Competing Interests: The authors declare no conflict of interest.

The aim of this study was to determine the prevalence of T helper 9 (Th9) lymphocytes in rheumatoid arthritis (RA) patients and to identify a possible association between the percentage of Th9 and the discontinuation of a biological treatment with an anti-tumor necrosis factor (TNF) (infliximab). We collected peripheral blood mononuclear cells (PBMCs) from 55 consecutive RA outpatients and 10 healthy controls. Among RA patients, 15 were not receiving any immunosuppressive drug, 20 were successfully treated with infliximab and 20 discontinued infliximab because of adverse events or inefficacy and were treated with other biological agents. PBMCs were cultured with/without infliximab 50 mg/L for 18 h, and the percentage of Th9 cells was assessed by means of flow cytometry. Th9 lymphocytes were identified as interferon gamma, interleukin (IL)4-, IL17-, IL9-secreting cluster of differentiation 4 (CD4)+ T cells. Cytometric analysis revealed no significant decrease in the percentage of Th9 cells after infliximab exposure in any of the groups, although it was lower in healthy controls than RA patients either before and after the infliximab stimulation assay. Th9 cells are IL-9-secreting T helper lymphocytes whose role in RA is still poorly known. IL-9 levels are increased in RA patients, in whom this cytokine plays a crucial role. Th9 cells are the major producers of IL-9, and their prevalence is higher in RA patients than in healthy subjects; however our experiment in vitro does not demonstrate an association between Th9 lymphocytes and the response to infliximab. Further studies are required to evaluate the real involvement of Th9 population in the immunogenicity of anti-TNF agents.

Long-term extension studies and observational drug registers have revealed an increased risk of serious infections in patients treated with anti-tumor necrosis factor agents, particularly infliximab, etanercept and adalimumab. The same may be true for the newer biological drugs rituximab, tocilizumab and abatacept, although this has yet to be confirmed by long-term observational studies. We review the risk of tuberculosis, herpes zoster and other opportunistic infections, and the recommendations for screening for tuberculosis and hepatitis B and C infections in patients with rheumatoid arthritis, with the aim of informing patients and encouraging greater awareness among physicians.

Purpose: The immunogenicity of anti-TNF-α drugs may affect their safety and efficacy. Infliximab (IFX), a chimeric monoclonal antibody, induces antibody formation in up to 60% of cases. Some studies have suggested the involvement of a Th1 response to TNFα blockers following immunization, but the triggering of Th17 responses has never been reported. The aim of this study is to investigate whether the immunogenicity of IFX affects the Th1, Th17 and Treg compartments in rheumatoid arthritis (RA) patients failing IFX therapy, and verify whether this may be responsible for treatment failure., Methods: The study involved 55 patients with RA (15 treatment-naïve patients; 20 IFX responders; 20 IFX non-responders) and 10 healthy controls. PBMCs were cultured in the presence/absence of IFX, and the variations in the percentage of Th1, Th17 and Treg lymphocytes following IFX treatment were analysed., Results: IFX-specific Th1 and Th17 responses and an increase in IL-21 production were observed in patients failing IFX (p < 0.01, p < 0.05, and p < 0.01 respectively). In contrast, IFX incubation reduced significantly Th1 and Th17 responses and IL-21 production (p < 0.05) in successfully-treated subjects, but did not affect these responses in healthy controls or treatment-naïve patients., Conclusions: RA patients may have impaired peripheral tolerance, which could favour the development of an aberrant immunological response to biological drugs. The loss of therapeutic effectiveness of IFX and the onset of adverse events may be due to a paradoxical activation of Th17 or Th1 lymphocytes following sensitisation, thus worsening the patients' inflammatory status.