Measurements of cytokine mRNA expression by quantitative polymerase chain reaction in studies of celiac disease

Cytokines are known to play a key regulatory role in immune responses. The onset or progression of immunopathology in various diseases is often associated with aberrant production of one or more cytokines. It is therefore of considerable interest to characterize cytokine "profiles" associated with disease processes. Many methods employed for identification and quantification of cytokines produced by different cell types rely on the responsiveness of indicator cell lines. Such bioassays are technically restrictive owing to the time required for performance and because of sensitivity and specificity problems. Enzyme-linked immunosorbent assays (ELISAs), on the other hand, detect both biologically active and inactive cytokines without discrimination. These assays are easy to use, but the commercial kits are usually expensive. Both bioassays and ELISAs are unable to identify actual cytokine production and do not account for cytokines consumed by cells. In addition, the minute amounts of cytokine protein often produced in autocrine or paracrine microenvironments may not be easily detectable in a sample, especially when tissue or cells are available in only small quantities (1). Furthermore, although cells producing cytokine protein may be detected by immunocyto/histochemistry, only a limited number of antibodies with good performance are available (2), and the possibility of confusing synthesis with cellular uptake of cytokines exists.