Analysis of allergic reaction in IgG4-related disease

It is reported that allergic disorders are often complicated to immunoglobulin (Ig)G4-related diseases (IgG4-RD) [1]. High expression of type 2 helper T (Th2) cytokines has been confirmed in the involved organs of this disease [2]. However, it is unknown whether allergic reactions to any allergen are the causes of IgG4-RD. Therefore, in this study, we investigated the involvement of allergic reactions in the pathogenesis of IgG4-RD by evaluating specific IgE for several allergens in patients and analyzing the relationship between levels of serum IgG4, IgE, and peripheral counts of eosinophils. The cases comprised 281 subjects with IgG4-related dacryoadenitis and sialadenitis (IgG4-DS) who visited Sapporo Medical University Hospital between April 1997 and December 2017. All subjects satisfied the comprehensive diagnostic criteria for IgG4-RD [3]. At the first visit, we interviewed the subjects regarding their allergic symptoms, determined the peripheral eosinophil counts, measured the levels of serum IgG, IgG4, and IgE, and performed screening for IgEs against specific allergens. We used the following enzyme-linked immunosorbent assay (ELISA) kits: Human IgG ELISA Kit (ab100547, Abcam, Cambridge, UK) and IgG4 Human ELISA Kit (BMS2095, Thermo Fisher Scientific K.K., Yokohama, Japan). The levels of serum IgE were measured using the radioimmunosorbent test. For the screening, IgEs against specific allergens were measured using the radioallergosorbent test. The following allergens were evaluated by fluorescence Enzyme Immunoassay: birch pollen, cedar pollen, moth scales, Dermatophagoides pteronyssinus, Poaceae pollens, weed pollens, food allergens, grain allergens, animal epithelia, and mold allergens. We measured specific IgEs using CAP system (Phadia 1000TM, Thermo Fischer Scientific Inc., Uppsala, Sweden). We analyzed for correlations between the laboratory data, including the peripheral eosinophil counts and the levels of serum IgG4 and IgE. We also compared the clinical features between the patients with IgEs against specific allergens (the positive group) and the patients without IgEs against specific allergens (the negative group).