Low Serum IgG4 in Systemic Sclerosis: Lessons from an Israeli Cohort.

Abstract

Background: Immunoglobulin 4 (IgG4) is the least abundant immunoglobulin in the sera of healthy individuals; however, its levels can vary in different diseases such as IgG4-related disease (high) or Sjögren's syndrome (low). While previous studies have suggested the importance of IgG4 in autoimmune diseases, the clinical and biological significance of high or low levels remains unclear.

Objectives: To investigate the association between IgG4 antibody levels and systemic sclerosis (SSc), as well as the clinical features of the disease.

Methods: We measured IgG4 levels in the sera of 74 SSc patients from the years 2000 to 2019 and compared them to IgG4 levels in 80 healthy donors from the Israeli national blood bank. We performed correlation analyses between IgG4 levels and various factors, including age, sex, disease subtype, disease duration, organs involved, and medications taken by the patients.

Results: Our findings revealed significantly lower IgG4 levels in SSc patients compared to healthy participants. SSc patients receiving steroid treatment exhibited prominently lower IgG4 levels. In addition, SSc patients with Raynaud's phenomenon tended to have lower IgG4 levels compared to those without Raynaud's phenomenon.

Conclusions: Our study demonstrates that IgG4 levels are lower in SSc patients. Further research is needed to elucidate whether this observation contributes to the etiology of the disease or if it represents a common manifestation among other autoimmune diseases.