title: Quantification of human interleukin 18 mRNA expression by competitive reverse transcriptase polymerase chain reaction.
abstract: Interleukin 18 (IL-18) is a recently identified cytokine, originally called interferon gamma inducing factor, due to its capacity to induce interferon gamma production in Th1 type cells. IL-18 is expressed by a wide variety of cell types including mononuclear phagocytes, osteoblasts, keratinocytes and adrenal cortex cells. To quantify human IL-18 mRNA expression in small-scale cell samples the authors developed a competitive reverse transcriptase polymerase chain reaction using a competitive template as an internal standard. This assay was demonstrated as a valid, sensitive and precise tool to quantify human IL-18 mRNA expression. IL-18 mRNA expression of primary peripheral blood monocytes, CD4(+)T cells, CD8(+)T cells, B cells and NK cells was assessed by competitive RT-PCR. Basal IL-18 expression could be detected in all types of peripheral blood mononuclear cells (PBMC). The kinetics of IL-18 mRNA expression in PBMC from healthy donors was defined in vitro after monocyte-specific (lipopolysaccharide LPS), T-cell-specific (anti-CD3) and polyclonal-unspecific stimulation (phytohaemagglutinin PHA). Only LPS led to a strong increase of IL-18 mRNA expression peaking after 2 h. These results indicate that IL-18 is expressed constitutionally by all major PBMC subtypes. However, only monocyte specific stimulation resulted in a significant induction of IL-18 mRNA expression suggesting activated monocytes e.g. in inflammation as the main source of IL-18 expression.
authors.affiliation: Medizinische Klinik III der Johann Wolfgang, Goethe Universität, Frankfurt, Germany.
authors.forename: S A
authors.initials: SA
authors.lastname: Klein
authors.forename: O G
authors.initials: OG
authors.lastname: Ottmann
authors.forename: K
authors.initials: K
authors.lastname: Ballas
authors.forename: T S
authors.initials: TS
authors.lastname: Dobmeyer
authors.forename: M
authors.initials: M
authors.lastname: Pape
authors.forename: E
authors.initials: E
authors.lastname: Weidmann
authors.forename: D
authors.initials: D
authors.lastname: Hoelzer
authors.forename: U
authors.initials: U
authors.lastname: Kalina
mesh_terms: D001667:Binding, Competitive; D006801:Humans; D020382:Interleukin-18 / Q000235:genetics*; D007963:Leukocytes, Mononuclear / Q000378:metabolism*; D016014:Linear Models; D012333:RNA, Messenger / Q000096:biosynthesis*; D015203:Reproducibility of Results; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D013698:Templates, Genetic
chemical_list: D020382:Interleukin-18; D012333:RNA, Messenger