Deregulated production of interleukin-4 (IL4) in autoimmune thyroid disease assayed with a new radioimmunoassay.

A sensitive, reproducible and specific radioimmunoassay for human interleukin-4 (IL4) has been developed. Using 125I-labeled IL4 and polyclonal rabbit antisera raised against recombinant human IL4, a competitive inhibition assay was developed which could detect 5 pg/ml of human IL4. Other interleukins, growth factors, hormones, peptides and lectins did not affect the assay. IL4 was measured in supernatants of culture media of stimulated human peripheral blood mononuclear cells (PBMC). Kinetics of IL4 production in PHA-stimulated PBMC from seven normal subjects revealed that the peak levels of IL4 were seen at 24 h and then declined. Peak IL4 levels in PHA stimulation of PBMC from untreated patients with autoimmune thyroid diseases (Graves' disease and chronic thyroiditis) were significantly higher than normal controls. However, after treatment, IL4 production decreased to normal. The present study demonstrates the usefulness of quantitating human IL4 produced by PBMC and that there exists a deregulated production of IL4 in autoimmune thyroid diseases.