Background The occurrence and clinical significance of IgG subclass deficiencies in rheumatoid arthritis (RA) has only been determined in small investigations (1, 2) and with different methods as the results are difficult to compare (3). Furthermore the deficiencies have never been analysed in detail in relation to factors as immune modulatory treatment, age, gender, smoking habits and other laboratory findings.
Objectives The present study aimed therefore to determine IgG subclass deficiencies in patients with RA and the identification of putative contributing factors to create a risk profile of patients treated with immune modulatory in view of immune deficiencies.
Methods We evaluated IgG subclass levels in blood samples of 539 patients with rheumatoid arthritis by an immunonephelometric assay. In addition, we determined age, gender, smoking habits, duration and activity of the disease (DAS 28), the degree erosions, number of infections as well as inflammatory markers to study an assumed relation to IgG levels.
Results According to laboratory standard values, we found IgG deficiencies in 19.9% of patients with a mean value (± standard deviation) of 10.4±2.8 g/l. Most frequent deficiencies of subclasses were observed for IgG1 (42.3%), while less prominent for IgG2 (7.2%), IgG3 (5.4%) and IgG4 (10.4%). Mean values of all patients of IgG-subclasses were 5.6±2.3 g/l for IgG1, 3.2±1.5 g/l for IgG2, 0.7±0.4 g/l for IgG3 and 0.4±0.5 g/l for IgG4. IgG1- and IgG2 deficiencies were more prevalent in older patients. In addition, smoking habits were closely associations with IgG2 deficiency while disease progression was related to IgG1 deficiency. A logistic regression revealed that patients with IgG deficiency have a significant higher risk of infections.
Conclusions An unexpected high occurrence rate of IgG and IgG subclass deficiencies was observed in our patients. We suggest therefore that the assessment of IgG and IgG subclass status should prevail the application of immune modulating drugs to prevent a potential risk of infectious diseases. Prospective studies are needed to investigate both the influence of immune modulating drugs on IgG and IgG subclass levels and on the immune defense reaction.
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Acknowledgements Thanks to the doctors of Ambulantes Rheumazentrum Erfurt for their support and the supervisor Prof. Dr. Rolf Bräuer.
Disclosure of Interest None declared