Cytokines generalized characteristics

Currently, immunoassay is the practical method of choice for measuring cytokines and their receptors. As cytolanes are proteins, specific antibodies can be raised against recombinant cytokines and have also been measured as an indicator of cytokine presence, The general characteristics of cytokine immunoassays are comparable with the classical immunoassays, with monoclonal, oligoclonal, or polyclonal antibodies all being used (see Chapter 9). The most popular formats are immunoradiometric assay (IRMA) and ELISA, which use a first monoclonal antibody for the capture and a second antibody labeled with a radioisotope or an enzyme. 

Bioassays are generally more sensitive than immunoassays for the measurement of cytokines in cell culture supernatants. The characteristics of calibration curves vary among different assays (Fig. 9) and limits of sensitivity must be set to use only the part of the curve that provides adequate precision. 

The human CXC chemokine family of cytokines, in their monomeric form, are less than 10 kDa, and are characteristically basic heparin-binding proteins. On a structural level, this family displays four highly conserved cysteine amino acid residues, with the first two cysteines separated by one nonconserved amino acid residue, hence the designation of CXC chemokines (68-77). In addition, another structural domain influences their biological behavior. The NH2 terminus of the majority of CXC chemokines contains three amino acid residues (Glu-Leu-Arg the ELR-motif) that precedes the first cysteine amino acid residue of the primary structure of these cytokines (68-77). This motif, in general, determines their binding on neutrophils and dictates whether these cytokines promote angiogenesis (57,78,79). 

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