Clinical immunological characteristics of anti-interferon-γ autoantibodies syndrome: a 3 year prospective cohort study.

Anti-interferon-γ autoantibodies (AIGAs) syndrome is susceptible to disseminated opportunistic infections due to increased AIGAs, but its clinical immunological characteristics remain unrecognized. We conducted a prospective cohort study between January 2021 and December 2023, recruiting patients with opportunistic infections who were categorized into AIGAs-positive and AIGAs-negative groups. Clinical immunological data and outcomes were documented. A subset of AIGAs-positive patients received glucocorticoid treatment, and its effectiveness was evaluated. A total of 238 patients were enrolled, with 135 AIGAs-positive and 103 AIGAs-negative patients. AIGAs-positive patients showed higher rates of multiple pathogen dissemination, shorter progression-free survival (PFS), and increased exacerbation frequency. They also showed elevated erythrocyte sedimentation rate (ESR), globulin (GLB), immunoglobulin (Ig)G, IgE, and IgG4 levels. Among the 70 AIGAs-positive patients monitored for at least six months, three subtypes were identified: high AIGAs titer with immune damage, high AIGAs titer without immune damage, and low AIGAs titer without immune damage. Of the 55 patients followed for 1 year, decreasing AIGAs titer and immune indices (GLB, IgG, IgE, IgG4) were observed. Among the 31 patients with high AIGAs titer and immune damage treated with low-dose glucocorticoids at the stable phase, reductions were observed in immune indices and AIGAs titer in 67.74% of cases. In summary, AIGAs-positive patients exhibit infectious and immunological characteristics. Elevated AIGAs, IgG, IgG4, and IgE indicate abnormal immune damages. AIGAs titer generally decrease over time. Stable-phase AIGAs-positive patients can be categorized into three subtypes, with those having high AIGAs titer and increased immune indices potentially benefitting from glucocorticoid treatment.