The capacity of interleukin‐4 to induce in vitro IgE synthesis by B cells of patients with common variable immunodeficiency

Interleukin‐4 (IL‐4) has been shown to induce IgE synthesis by peripheral blood mononuclear cells (PBMC) of normal donors in vitro. However, induction of PBMC of patients with common variable immunodeficiency (CVI) with IL‐4 resulted in IgE production in only two out of eight cases tested. PBMC of the first patient that produced IgE in response to IL‐4 also secreted normal levels of IL‐4 upon activation. PBMC of the second patient secreted very low levels of IL‐4 in vitro which may account for the very low serum IgE levels in this patient. Of the other six patients who had very low serum IgE levels and whose PBMC failed to produce IgE in response to IL‐4 in vitro, five did not secrete IL‐4 upon in vitro activation. The capacity of the T cells to produce IL‐4 was intact in the sixth patient. Collectively our data indicate the PBMC of the majority of patients with CVI are defective since they failed to respond appropriately to IL‐4 and they failed to produce IL‐4, contributing to the view that CVI is a heterogeneous disorder in which a variety of T and B cell defects occur.