INTENDED USE

This Human Interleukin-6 soluble receptor ELISA Kit is to be used for the in vitro quantitative determination of human interleukin-6 soluble receptor (IL-6sR) concentrations in serum, plasma, cell culture supernatant, and other biological fluids. This kit is intended for LABORATORY RESEARCH ONLY and is not to be used for diagnostic or therapeutic procedures.

INTRODUCTION

Interleukin-6 (IL-6) is a multifunctional cytokine produced by a wide variety of cell types including monocyte/macrophages, T cells, fibroblasts, hepatocytes, vascular endothelial cells, cardiac myxomas, bladder cell carcinomas, myelomas, astrogliomas, and glioblastomas. The effects of IL-6 on different cell types are numerous and varied. These activities include: stimulation of B cell differentiation and antibody secretion; action as a co-stimulant withPHAor Con A to increase IL-2 production and IL-2 receptor expression by T cells; enhancement of differentiation of cytotoxic T cells; action as a growth factor for mature thymic or peripheral T cells, myelomas, hybridomas, plasmacytomas, keratinocytes, and mesangial cells; colony-stimulating activity on hematopoetic cells; induction of neuronal cell differentiation; induction of maturation of megakaryocytes; and stimulation of production of acute phase response proteins by hepatocytes. These various activities indicate that IL-6 plays a major role in the mediation of the inflammatory and immune responses initiated by infection or injury. Elevated IL-6 levels have been reported to be associated with a variety of diseases, including autoimmune diseases, mesangial proliferative glomerulonephritis, psoriasis, and malignancies such as plasmacytomas and myelomas. For reviews of the properties and activities of IL-6, see references 1 to 3.

The biological activities of IL-6 are initiated by binding of the cytokine to a high affinity receptor complex consisting of two membrane glycoproteins; an 80 kDa component receptor that binds IL-6 with low affinity (IL-6R) and a signal-transducing component of 130 kDa (gp130) that does not bind IL-6 by itself, but is required for high affinity binding of IL-6 by the complex. IL-6R and gp130 have been cloned, sequenced and expressed (4-7).

A soluble form of the IL-6 R with a molecular weight of approximately 50 kDa has been found in the urine of healthy adult humans (8), in culture medium conditioned by the growth of a human myeloma cell line (9), in culture supernatants from PHA-stimulated human PBMC and HTLV-1 positive T cell lines (10) and in the serum of HIV-seropositive blood donors (10). This soluble form of the receptor apparently arises from proteolytic cleavage of membrane-bound IL-6R. Soluble forms of human and mouse IL-6 have also been constructed by insertion of termination codons into the regions of the IL-6R cDNAs encoding the external portions of the receptors and prior to the transmembrane domains (11, 12). These soluble receptors have been expressed in COS7 and CHO cells (11, 12) and have been shown to bind IL-6 in solution and to augment the activity of IL-6 as a result of the binding of the IL-6/IL-6 sR complex to membrane-bound gp130 (11, 12). The regulation in vivo of the shedding of the soluble IL-6Rs and the function and significance of these soluble receptors in biological fluids is not currently understood. It has been suggested, however, that pathogical states involving elevated levels to IL-6 might also be associated with increased production of soluble IL-6Rs (10).

This IL-6sR ELISA is a 3.5-hour solid phase immunoassay readily applicable to measureIL-6sR levels in serum, plasma, cell culture supernatant, and other biological fluids in the range of 0 to 2000 pg/mL. It showed no cross reactivity with other cytokines tested. This IL-6sR ELISA is expected to be effectively used for further investigations into the relationship between IL-6sR and the various conditions mentioned.