title: Methodologic issues in the measurement of interleukin-16 in clinical blood samples using immunoassays.
abstract: Quantitation of interleukin-16 (IL-16) in clinical blood samples has strongly increased, since IL-16 appears to be involved in the pathogenesis of several inflammatory diseases. IL-16 is synthesized in the cell cytoplasm as precursor protein (pro-IL-16), which can be processed by caspase-3 into N-terminal (N-IL-16) and C-terminal (C-IL-16) fragments. C-IL-16 is described to be subsequently secreted. Using commercially available IL-16 ELISA, a pro-IL-16 ELISA and immunoprecipitation analysis, we investigated, whether type and handling of blood samples influence IL-16 quantitation and whether existing IL-16 ELISA are specific for C-IL-16. We observed that cell-rich plasma samples reflect falsely-elevated IL-16 concentrations due to cell contaminations. Interestingly, not C-IL-16, but pro-IL-16 represents the major IL-16 form in cell-rich plasma samples. Notably, commercially IL-16 ELISA could not distinguish between C-IL-16 and pro-IL-16. Thus, cell-rich plasma samples should not be used for IL-16 measurements and new methods are necessary for quantitation of C-IL-16 and pro-IL-16 uniquely.
authors.affiliation: Institute of Molecular and Clinical Immunology, Otto-von-Guericke-University Magdeburg, Magdeburg, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Goihl
authors.forename: Anna-Maria
authors.initials: AM
authors.lastname: Rolle
authors.forename: Thilo
authors.initials: T
authors.lastname: Kähne
authors.forename: Annegret
authors.initials: A
authors.lastname: Reinhold
authors.forename: Sabine
authors.initials: S
authors.lastname: Wrenger
authors.forename: Dirk
authors.initials: D
authors.lastname: Reinhold
mesh_terms: D001773:Blood Cells / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005189:False Positive Reactions; D006801:Humans; D019410:Interleukin-16 / Q000097:blood*; D010949:Plasma / Q000166:cytology; D011498:Protein Precursors / Q000097:blood
chemical_list: D019410:Interleukin-16; D011498:Protein Precursors; C105950:interleukin 16 precursor