INTENDED USE

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

INTRODUCTION

Interleukin 6 (IL-6) is a multifunctional protein that plays important roles in host defense, acute phase reactions, immune responses, and hematopoiesis.⁽¹⁾ Synonyms for IL-6 include: B cell stimulatory factor-2 (BSF-2),⁽²⁾ hybridoma/plasmacytoma growth factor,⁽³⁾ hepatocyte stimulating factor, cytotoxic T cell differentiation factor and macrophage-granulocyte inducing factor 2A (MGI-2A).⁽¹⁾ IL-6 is expressed by a variety of normal and transformed cells including T cells, B cells, monocytes/macrophages, fibroblasts, hepatocytes, keratinocytes, astrocytes, vascular endothelial cells, mesangial cells, osteoblasts, carcinomas, sarcomas, myelomas, glioblastomas, and melanomas. The production of IL-6 is up-regulated by numerous signals including mitogenic or antigenic stimulation, lipopolysaccharide, calcium ionophore, IL-1, IL-2, IFN, TNF, PDGF, and viruses. IL-4 and IL-13 inhibit IL-6 expression in monocytes. ^(4-6)

Natural human and murine IL-6 are glycoproteins containing N-and/or O-linked carbohydrates (human IL-6 contains two potential N-glycosylation sites, while mouse IL-6 has none). In comparison with mouse IL-6, human IL-6 exhibits approximately 65% sequence homology at the nucleotide level, and 42% homology at the amino acid level. Although human and mouse IL-6 are equally active on mouse cells, mouse IL-6 is not active on human cells.

IL-6 is predicted to have a four helix-bundle type tertiary structure found in a number of other cytokines including growth hormone, EPO, G-CSF, OSM, IL-11, CNTF, LIF, MGF, Prolactin, etc. ^(7-9) The gene structures of these cytokines also show varying degrees of relatedness. Based on these criteria, it has been suggested that these cytokines evolved from a common ancestral gene. Results of structure-function studies of IL-6 and other four a-helix bundle cytokines indicated that the c-terminal (helix D) regions of these cytokines are primarily responsible for binding to the receptors.^{(1. 4)}

Interleukin 6 exerts multiple functions on numerous target cells. IL-6 plays an important role in immune functions. It has effects on B cell differentiation and antibody production, on cytotoxic T cell differentiation, on T cell activation, growth and differentiation, and on the induction of IL-2Ra chain expression and IL-2 production in T cells.^(11-13) In hemopoiesis, IL-6 has blast cell growth factor activity and can synergize with IL-3 to shorten the G₀ period of early hemopoietic progenitors.⁽¹⁴⁾ In addition, IL-6 has been found to synergize with IL-3 in megakaryocyte development, increasing platelet numbers in vivo and the number, size and average ploidy value of megakaryocyte colonies formed from mouse or human bone marrow cells in vitro.^(15-18) Similarly to IL-11 and LIF, IL-6 can induce the synthesis of hepatic acute phase proteins both in vivo and in vitro.⁽¹⁹⁾ IL-6 has growth factor activities and will stimulate the growth of hybridomas, plasmacytomas, myelomas, sarcomas,^{(20, 21)} carcinomas,⁽²²⁾ EBV-transformed B cells,⁽²³⁾ keratinocytes, and mesangial cells. In contrast to its growth stimulatory activities, IL-6 is also a growth inhibitor for a number of leukemia and carcinoma cell lines. Additional bioactivities attributed to IL-6 include: induction of terminal differentiation of M1 myeloid leukemic cells;⁽²⁴⁾ the differentiation and survival of neuronal cells;^{(25, 26)} and the activation of osteoclast development.⁽¹⁰⁾ Although IL-6 was also discovered as an antiviral factor produced by human diploid fibroblasts, the question of whether or not IL-6 has antiviral activity is controversial. Many groups have been consistently unable to find any antiviral activity for recombinant human IL-6.⁽¹⁾ The various activities of IL-6 described above suggest that this factor plays a major role in the mediation of the inflammatory and immune responses.

This IL-6 ELISA is a 3.5 hour solid phase immunoassay readily applicable to measure IL-6 levels in cell culture supernatant, serum, plasma, and other biological fluids in the range of 0 to 400 pg/mL. It showed no cross reactivity with various other cytokines superfamily proteins.

CITATIONS

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2. Khan A, Ali Z.Normal Ranges for Acute Phase Reactants (Interleukin-6, Tumour Necrosis Factor-alpha and C-reactive Protein) in Umbilical Cord Blood of Healthy Term Neonates at the Mount Hope Women"s Hospital, Trinidad. West Indian Med J 2014; 5(63):465-9.

3. Çeliksular MC, Saraçoğlu A, Yentür E.The Influence of Oral Carbohydrate Solution Intake on Stress Response before Total Hip Replacement Surgery during Epidural and General Anaesthesia. Turk J Anaesthesiol Reanim 2016; 3(44):117-23.

4. Guo Y, Shi G, Wan H, Zhou M.Hedgehog signaling regulates the expression levels of inflammatory mediators in cigarette‑induced airway inflammation. Mol Med Rep 2018; 6(17):8557-8563.

5. Zhang W, Mao S, Shi D, Zhang J, Zhang Z, Guo Y, Wu Y, Wang R, Wang L, Huang Y, Yao X.MicroRNA-153 Decreases Tryptophan Catabolism and Inhibits Angiogenesis in Bladder Cancer by Targeting Indoleamine 2,3-Dioxygenase 1. Front Oncol. 2019; 10(9):619.

6. Zhang W, Zhang J, Zhang Z, Guo Y, Wu Y, Wang R, Wang L, Mao S, Yao X.Overexpression of Indoleamine 2,3-Dioxygenase 1 Promotes Epithelial-Mesenchymal Transition by Activation of the IL-6/STAT3/PD-L1 Pathway in Bladder Cancer. Transl Oncol. 2019; 12(3):485-492.