An improved assay for the detection of interleukin 1

A 24 h, highly sensitive assay for detection of interleukin 1 (IL-1) is described. A thioguanine-resistant mutant of the murine lymphoma cell line LBRM 33 was selected (LBRM TG6). When this cell line was incubated with low concentrations of PHA and IL-1 it produced interleukin 2 (IL-2). IL-2-dependent HT2 cells were co-cultured with the LBRM cells to measure the released IL-2. Prior to addition of tritiated thymidine to the co-culture, hypoxanthine and azaserine were added to metabolically block DNA synthesis by LBRM TG6 cells. This resulted in a sensitive, short term assay requiring minimal technical manipulations and characterized by a high signal to noise ratio.