Interleukin-21 Levels May Indicate Disease Activity in AAV Patients, Pilot Study Suggests

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by Alice Melão |

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High blood levels of a signaling molecule called interleukin-21, or IL-21, may identify patients with active ANCA-associated vasculitis (AVV), a pilot study suggests.

The study, “Serum interleukin-21 positivity could indicate the current activity of antineutrophil cytoplasmic antibody-associated vasculitis: a monocentric prospective study,” was published in the journal Clinical Rheumatology.

IL-21 is an important signaling molecule that modulates the activity and responsiveness of immune cells in the body. The molecule has been identified as an important contributor to autoimmune disorders, as it induces B-cell maturation and the production of autoantibodies, which are antibodies that target the host’s own tissues.

In recent studies, the T-cells that produce IL-21 have been implicated in the development and exacerbation of AAV lesions, so researchers hypothesize that levels of IL-21 in circulation might correlate with disease activity in these patients.

To address this, a team at the Yonsei University College of Medicine in Seoul examined IL-21 levels in 60 AAV patients included in the Severance Hospital ANCA-associated VasculitidEs (SHAVE) cohort from November 2016 to May 2018.

Participants had a mean age of 59.3 years and a mean disease duration of 21.4 months. Among them, 31 had microscopic polyangiitis (MPA), 18 had granulomatosis with polyangiitis (GPA), and 11 had eosinophilic granulomatosis with polyangiitis (EGPA).

Researchers detected signs of IL-21 in 16 patients (26.7%), who more often had generalized AAV and lung symptoms than those who tested negative for this molecule.

Next, the team compared IL-21 blood levels in AAV patients with those of patients with other autoimmune diseases, including rheumatoid arthritis and systemic lupus erythematosus (SLE), and healthy volunteers.

Mean IL-21 levels in AAV patients were significantly lower than in SLE patients and the control group. Still, the proportion of patients that were positive for IL-21 was similar among the different groups, ranging from 26.7% in the AAV group up to 45.2% in the SLE group.

Analysis of IL-21 blood levels throughout a follow-up period of six months in five AAV patients who were initially positive showed they became negative following a reduction in disease activity, as determined by the Birmingham vasculitis activity score (BVAS).

These results suggest that “serum IL-21 positivity might be a useful biomarker to indicate the disease activity of AAV,” according to the researchers.

Additional studies including a larger number of AAV patients with longer follow-up data are needed to better understand the clinical implications of IL-21 blood levels and its prognostic and diagnostic potential for these patients, they said.