Quantitation of biologically active IL-1 by a sensitive assay based on immobilized human IL-1 receptor type II (IL-1R II)

Abstract

A rapid and sensitive solid-phase radioassay is described for the quantitative detection of human interleukin-1 (IL-1) based on its capability to bind the nitrocellulose-immobilized IL-1 receptor solubilized from plasma membranes of a subclone of the human B cell lymphoma Raji. The assay can detect human IL-1β levels as low as 1 × 10 −11 M, both in physiological buffers and in human plasma. Much lower sensitivity was observed for human IL-1α (3.7 × 10 −9 M) and murine IL-1β (2 × 10 −9 M). This assay has the advantage to specifically detect only the correctly folded biologically active IL-1. Simple pretreatment procedure that selectively removes IL-1β from samples has been devised so that the ratio of the two IL-1s isoforms in the sample can be precisely determined. This assay represents a fast method for the simultaneous-testing of large numbers of biological samples.