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Pitfalls in Measuring Cytokines
- Samir Kapadia, MD;
- Guillermo Torre-Amione, MD, PhD; and
- Douglas L. Mann, MD
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TO THE EDITOR:
Casey and colleagues [1] note the potential importance of measuring cytokine levels in patients with systemic sepsis, whereas Dinarello and Cannon [2] detail many of the pitfalls associated with assaying cytokine levels. We report some other difficulties inherent in measuring “immunoreactive” tumor necrosis factor (TNF)- α by enzyme-linked immunosorbent assay (ELISA). As noted by Casey and colleagues [1], the assessment of TNF-α immunoreactivity reflects the level of the biologically active and inactive forms of TNF-α. However, the level of immunoreactive TNF-α is greatly influenced by the type of monoclonal antibody used in the ELISA kit, as well as by the presence of type I and type II TNF-binding proteins (soluble receptors) in the serum during septic shock [3]. This point is illustrated in Figure 1. In the ELISA kit used by Casey and colleagues [1] (T Cell Science, Cambridge, Massachusetts), the level of TNF-α immunoreactivity was masked by 75% and 60%, respectively, in the presence of type 1 TNF-binding proteins and type 2 TNF-binding proteins. In contrast, the level of immunoreactive TNF-α measured by an ELISA kit from a second vendor (Genzyme Corp., Cambridge, Massachusetts) was not affected by the type 1 proteins, whereas TNF-α immunoreactivity was masked by 80% in the presence of the type 2 proteins. Finally, levels of immunoreactive TNF-α measured by an ELISA kit from a third vendor (R & D Systems, Minneapolis, Minnesota) were not masked by either type of protein.
Although Casey and colleagues [1] have made an important contribution regarding the clinical significance of cytokine profiles in septic shock, it is critically important for the scientific community to standardize the methods used to measure cytokine levels in future trials.
The Editors welcome submissions for possible publication in the Letters section. Authors of letters should:
•Include no more than 300 words of text, three authors, and five references
•Type with double-spacing
•Send three copies of the letter, an authors' form signed by all authors, and a cover letter describing any conflicts of interest related to the contents of the letter.
Letters commenting on an Annals article will be considered if they are received within 6 weeks of the time the article was published. Only some of the letters received can be published. Published letters are edited and may be shortened; tables and figures are included only selectively. Authors will be notified that the letter has been received. If the letter is selected for publication, the author will be notified about 3 weeks before the publication date. Unpublished letters cannot be returned.
Annals welcomes electronically submitted letters.
- Copyright ©2004 by the American College of Physicians
