A cell surface ELISA to detect interleukin-4-induced class II MHC expression on murine B cells

A sensitive cell surface ELISA is described to detect interleukin-4 (IL-4)-induced major histocompatibility complex class II expression on murine B cells. The ELISA is performed on B cells cultured for 16 h in the presence of purified IL-4 or T cell-derived supernatants. A sandwich technique employing a biotin-conjugated monoclonal anti-I-E antibody followed by avidin-conjugated alkaline phosphatase is used to detect enhanced I-E MHC antigen expression on the B cells. Detection of I-E induced by both purified IL-4 and a T cell-derived supernatant was highly reproducible and sensitive using this method. Other lymphokines were found to be negative for the induction of I-E. The assay is easily performed and many sample supernatants can be rapidly screened for IL-4 activity. In addition, a general method for the removal of endogenous inhibitors of lymphokines from complex supernatants is described.