Effect of Interleukin-29 on Interferon-α Secretion by Peripheral Blood Mononuclear Cells

Objective: the effect of interleukin (il)-29, a new therapeutic agent similar to type i interferons(ifns), on ifn-? secretion of human plasmacytoid dendritic cells (pdcs) hasnot been studied. therefore, in this study, we aimed to clarify the effect of il-29 on ifn-?secretion of pdcs using human peripheral blood mononuclear cells (pbmcs) in the presenceof cytosine-phosphate-guanosinemotif-containing oligodeoxy nucleotides (cpg).materials and methods: in this experimental and prospective study, pbmcs were obtainedfrom 11 healthy volunteers and divided into four culture conditions: i. control, ii.cpg treatment, iii. il-29 treatment and iv. cpg plus il-29 treatment. the amount of ifn-?secretion was measured from each culture supernatant by flow cytometry using the flowcytomixapparatus (ebioscience, vienna, austria). fractional ifn-? production of the culturedpbmcs was measured by intracellular staining using the cytomics fc 500 system(beckman coulter, brea, ca, usa) with cxp software.results: the mean ± standard deviation (sd) of supernatant ifn-? secretion per pdc/?l was5.7 ± 9.3 pg/ml/count/?l for condition i, 1071.5 ± 1026.6 pg/ml/count/?l for condition ii, 14.1± 21.1 pg/ml/count/?l for condition iii, and 1913.9 ± 1525.9 pg/ml/count/?l for condition iv.there were statistically significant differences between conditions i and ii as well as betweenconditionsii and iv. intracellular ifn-? production was only detectable in the pdc fraction fromone culture; the production amount was similar between the cells treated with cpg and thosetreated with cpg plus il-29. natural killer (nk) cell production of ifn-? was observed in two outof three cultures and one culture showed ifn- ? production in the monocyte fraction.conclusion: il-29 alone did not show any effect on ifn-? secretion of pbmcs. however,the addition of cpg along with il-29 enhanced ifn-? secretion of pbmcs. given thatpdcs are the major secretors of ifn-? in peripheral blood, this result has suggested thepossibility that il-29 has an enhancing effect in human pdc ifn-? secretion. although thesupernatant ifn-? secretion was not directly correlated with pdcs’s intracellular ifn-?production in this study, prolonged incubation of pdc and other pb subsets with cpgor il-29 for over 4 hours could be applied in future studies. these studies would help toelucidate the mechanism of action of il-29 in human pdcs associated with viral infections.