effect of interleukin-29 on interferon-α secretion by peripheral blood mononuclear cellsammatory root resorption

objective: the effect of interleukin (il)-29, a new therapeutic agent similar to type i interferons (ifns), on ifn-α secretion of human plasmacytoid dendritic cells (pdcs) has not been studied. therefore, in this study, we aimed to clarify the effect of il-29 on ifn-α secretion of pdcs using human peripheral blood mononuclear cells (pbmcs) in the presence of cytosine-phosphate-guanosinemotif-containing oligodeoxy nucleotides (cpg). materials and methods: in this experimental and prospective study, pbmcs were obtained from 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-α secretion was measured from each culture supernatant by flow cytometry using the flowcytomix apparatus (ebioscience, vienna, austria). fractional ifn-α production of the cultured pbmcs 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-α secretion per pdc/μl was 5.7 ± 9.3 pg/ml/count/μl for condition i, 1071.5 ± 1026.6 pg/ml/count/μl for condition ii, 14.1 ± 21.1 pg/ml/count/μl for condition iii, and 1913.9 ± 1525.9 pg/ml/count/μl for condition iv. there were statistically significant differences between conditions i and ii as well as betweenconditions ii and iv. intracellular ifn-α production was only detectable in the pdc fraction from one culture; the production amount was similar between the cells treated with cpg and those treated with cpg plus il-29. natural killer (nk) cell production of ifn-α was observed in two out of three cultures and one culture showed ifn- α production in the monocyte fraction. conclusion: il-29 alone did not show any effect on ifn-α secretion of pbmcs. however, the addition of cpg along with il-29 enhanced ifn-α secretion of pbmcs. given that pdcs are the major secretors of ifn-α in peripheral blood, this result has suggested the possibility that il-29 has an enhancing effect in human pdc ifn-α secretion. although the supernatant ifn-α secretion was not directly correlated with pdcs’s intracellular ifn-α production in this study, prolonged incubation of pdc and other pb subsets with cpg or il-29 for over 4 hours could be applied in future studies. these studies would help to elucidate the mechanism of action of il-29 in human pdcs associated with viral infections.