Pitfalls in cytokine analysis in inflammatory bowel disease.

Analysis of cytokine production and function is an indispensable tool to study Crohn's disease and ulcerative colitis. This analysis has generated a tremendous amount of data, but a clear interpretation of results has been hampered by limited attention paid to several patient- and sample-related pitfalls. These include: clinical parameters; the relative value of circulating vs. intestinal cytokine levels; the selection of tissue specimens and their processing method; the specific cellular source of each cytokine; the effect of cytokine inducers; and the technique utilized to obtain qualitative or quantitative data on cytokine protein or mRNA. Once all of these crucial variables are taken into proper perspective, a better understanding will emerge of the true role of cytokines in the pathogenesis of inflammatory bowel disease.