Interleukin-18 enhances the production of interferon-gamma (IFN-gamma) by allergen-specific and unspecific stimulated cord blood mononuclear cells.
BACKGROUND
IL-18 is a pleiotropic cytokine involved in the polarisation of T-cell response. This study was performed to determine whether or not IL-18 is detectable in phytohemagglutinin (PHA) or betalactoglobulin (BLG) stimulated supernatants of cord blood mononuclear cells (CBMC) and to study the in vitro effect of IL-18 on the interferon (IFN)-gaamma and IL-13 release of CBMC of healthy neonates.


METHODS
CBMC of neonates were isolated by Ficoll density centrifugation. The cytokines IFN-gamma, IL-13 and IL-18 in the cell culture supernatants were measured using the ELISA technique following stimulation with a unspecific (PHA 20 microg/ml) and an allergen-specific stimulus (BLG 25 microg/ml). In order to study the in vitro effect of IL-18, CBMC were stimulated either with medium alone or with IL-18, IL-18 + PHA and IL-18 + BLG.


RESULTS
IL-18 levels in supernatants of CBMC were low and did not vary significantly between unstimulated and PHA or BLG stimulated cell cultures (median 21.4; 23.5 and 15.5 pg/ml, respectively). IFN-gamma and IL-13 levels were significantly higher in response to PHA and BLG (PHA: IFN-gamma, 6154; IL-13, 4357; BLG: IFN-gamma, 801; IL-13, 249 pg/ml) compared to unstimulated cell cultures. The addition of IL-18 to PHA or BLG stimulated CBMC significantly enhanced the IFN-gamma release (PHA: 6154; PHA + IL-18: 13474, p = 0.0001; BLG: 801; BLG + IL-18: 1077, p = 0.008). In comparison to incubation without IL-18, the release of IL-13 was invariable or even reduced, when CBMC were stimulated with PHA + IL-18 (4026, p = 0.16) or BLG + IL-18 (124, p = 0.0001) compared to stimulation of CBMC with PHA (4357 pg/ml) or BLG (249 pg/ml) alone.


CONCLUSIONS
IL-18 is detectable in supernatants of CBMC. We observed a significant effect of IL-18 + PHA as well as IL-18 + BLG on IFN-gamma release in vitro. Based on our findings we conclude that IL-18 could act as a strong TH1-inducing factor on stimulated CBMC also in vivo.
Ngoumou
Gonza
G
University Children's Hospital, Mathildenstrasse 1, D-79106 Freiburg, Germany.
Schaefer
Doerte
D
Mattes
Joerg
J
Kopp
Matthias Volkmar
MV
D000485:Allergens / Q000276:immunology*; D005312:Fetal Blood / Q000166:cytology*; D006801:Humans; D007371:Interferon-gamma / Q000096:biosynthesis* / Q000276:immunology*; D018793:Interleukin-13 / Q000378:metabolism; D020382:Interleukin-18 / Q000494:pharmacology*; D007782:Lactoglobulins / Q000494:pharmacology; D007963:Leukocytes, Mononuclear / Q000187:drug effects* / Q000276:immunology* / Q000378:metabolism; D010835:Phytohemagglutinins / Q000494:pharmacology; D013379:Substrate Specificity
D000485:Allergens; D018793:Interleukin-13; D020382:Interleukin-18; D007782:Lactoglobulins; D010835:Phytohemagglutinins; D007371:Interferon-gamma