Description
Two distinct IL-lRs have been identified, termed type I and type II. The type I IL-lR is an 80-kDa glycoprotein found predominantly on T cells and fibroblasts, whereas the type II IL-lR is a 60- to 65-kDa molecule that is expressed on activated T cells, B cells, monocytes, and neutrophils. Evidence suggests that the type II IL-lR is not signal- transducing, and its function on the cell surface is unknown. The action of IL-1 is modulated not only by IL-lra but also by the release of a type II soluble IL-iR (sIL-lR). This 47-kDa soluble receptor is present in normal human plasma, serum, and synovial inflammatory exudate and in culture supernatants of activated peripheral blood mononuclear cells and neutrophils. sIL-lR is also released from the human B-cell Burkitt lymphoma cell line Raji, which expresses only type II IL-1R