Quantification of recombinant human interleukin-1 alpha by a specific two cell immunobioassay

The detection of picogram quantities of recombinant human IL-1 alpha in human and rat serum was accomplished by a sensitive and specific two cell immunobioassay. The specificity is provided by an IL-1 alpha specific mouse IgM monoclonal antibody which is non-neutralizing thus allowing for the addition of the EL-4 NOB-1 cell line directly to the IL-1 alpha monoclonal antibody complex. The above cell line is then converted to an IL-2 producer line in response to the captured IL-1 alpha. Supernatant from the EL-4 NOB-1 cells is then added to the IL-2 dependent CTLL-2 line and cell proliferation measured by thymidine incorporation. This assay has the advantage of specificity provided by the antibody capture step, sensitivity provided by the EL-4 NOB-1 line (1-50 pg/ml) and finally ease of maintenance of the responder cell line which requires no feeder cells or mitogens. Data are reported on the sensitivity, precision, reproducibility and specificity of the assay, the stability of rhIL-1 alpha in serum and the recovery of rhIL-1 alpha from serum. We also report on the use of this procedure to assay samples from rats given ascending doses of rhIL-1 alpha.