Involvement of interleukin (IL)‐13, but not IL‐4, in spontaneous IgE and IgG4 production in nephrotic syndrome

Abstract Nephrotic syndrome (NS) is a renal disease characterized by proteinuria and hypoalbuminemia. In NS patients without any allergic disease, serum IgE and IgG4 levels were selectively increased, and peripheral blood mononuclear cells (MNC) spontaneously produced IgE and IgG4. T cells produced interleukin (IL)‐13 spontaneously, and B cells constitutively expressed IL‐13 receptors (IL‐13R). In addition, T cells stimulated surface IgE‐negative (sIgE − ) and sIgG4 − B cells to produce IgE and IgG4, respectively, and IgE and IgG4 production was specifically blocked by anti‐IL‐13 antibody (Ab). MNC from atopic dermatitis (AD) patients also produced IgE and IgG4 spontaneously. However, in AD patients, T cells spontaneously produced IL‐4, but not IL‐13, and B cells constitutively expressed IL‐4R, but not IL‐13R. T cells stimulated sIgE − and sIgG4 − B cells to produce IgE and IgG4, respectively, and the production was specifically blocked by anti‐IL‐4 Ab. On the other hand, sIgE + and sIgG4 + B cells from both NS and AD patients spontaneously produced IgE and IgG4, respectively, and this production was not affected by T cells, anti‐IL‐4 Ab, or anti‐IL‐13 Ab. These results indicate that IL‐13 is involved in the enhanced production of IgE and IgG4 in NS, while IL‐4 is involved in these responses in AD.