Decreased interleukin-12 (IL-12) from activated cord versus adult peripheral blood mononuclear cells and upregulation of interferon-gamma, natural killer, and lymphokine-activated killer activity by IL-12 in cord blood mononuclear cells.
Interleukin-12 (IL-12) is a critical cytokine regulating natural killer (NK) and T-cell function. We hypothesized that the impaired ability of cord blood (CB) to produce normal adult levels of IL-12 in response to stimulation may contribute to the immaturity of CB immunity. Furthermore, exogenous IL-12 may compensate for the immaturity in CB cellular immunity and have the potential for immunotherapy post cord blood transplantation. We compared the expression and production of IL-12 from activated cord versus adult mononuclear cells (MNC), regulatory mechanisms associated with IL-12 expression in CB MNC, and the effects of IL-12 on induction of CB interferon (IFN)-gamma production, NK, and lymphokine-activated killer (LAK) cytotoxicity. Northern analysis and enzyme-linked immunosorbent assay were performed in lipopolysaccharide (LPS)-stimulated CB and adult peripheral blood (APB) MNC. IL-12 mRNA expression was induced within 6 hours with LPS (10 micrograms/ml) and reached peak levels at 12 hours in both CB and APB MNC. However, IL-12 mRNA expression and protein accumulation in CB MNC were 35.8% +/- 4.84% (12 hours, n = 11, P < .05), and 17.6% +/- 1.7% (24, 72, 96 hours, n = 9, P < .05) respectively, when compared with APB MNC. Nuclear run-on assays showed no differences between CB and APB MNC in both the basal levels of transcription and the degree of transcriptional activation. However, the half-life of IL-12 p40 mRNA was approximately threefold lower in activated CB MNC than in activated APB MNC (CB: 114 +/- 3.0 minutes v APB: 353 +/- 7.8 minutes, n = 3, P < .05). Exogenous IL-12 (10 U/mL) induced a significant increase of IFN-gamma from both CB and APB MNC (24 hours, 72 hours, P < .05, n = 3). The stimulated CB IFN-gamma level reached comparable levels produced by unstimulated APB. IL-12 treatment also significantly enhanced CB NK cytotoxicity against K562 and NB-100 cell lines to the comparable levels of APB (P < .05, n = 4). CB MNC was more responsive to IL-12 stimulation with respect to IFN-gamma production, NK, and LAK cytotoxicity when compared with APB. The present study suggests that IL-12 mRNA and protein expression is decreased in activated CB. This discrepancy in IL-12 production is secondary, at least in part, to the altered posttranscriptional regulation. The impaired, ability of CB MNC to produce IL-12 in response to stimulation may contribute to the decrease in IFN-gamma production and NK cytotoxicity. However, IL-12 enhanced IFN-gamma and NK activity in CB MNC up to the comparable levels of APB MNC. These findings suggest that reduced expression and production of IL-12 from activated CB may contribute to the immaturity in CB cellular immunity and contribute, in part, to decreased graft-versus-host disease following CB stem cell transplantation.
Lee
S M
SM
Division of Hematology/Oncology and Blood and Bone Marrow Transplantation, Children's Hospital of Orange County, CA 92668, USA.
Suen
Y
Y
Chang
L
L
Bruner
V
V
Qian
J
J
Indes
J
J
Knoppel
E
E
van de Ven
C
C
Cairo
M S
MS
D000328:Adult; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic / Q000187:drug effects; D005312:Fetal Blood / Q000166:cytology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006087:Graft vs Host Reaction; D006207:Half-Life; D018380:Hematopoietic Stem Cell Transplantation; D006801:Humans; D007231:Infant, Newborn; D007371:Interferon-gamma / Q000378:metabolism*; D018664:Interleukin-12 / Q000096:biosynthesis / Q000097:blood* / Q000235:genetics / Q000494:pharmacology; D015979:Killer Cells, Lymphokine-Activated / Q000187:drug effects*; D007694:Killer Cells, Natural / Q000187:drug effects*; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism
D008070:Lipopolysaccharides; D012333:RNA, Messenger; D018664:Interleukin-12; D007371:Interferon-gamma