title: Impaired production of IL-12 in systemic lupus erythematosus. III: deficient IL-12 p40 gene expression and cross-regulation of IL-12, IL-10 and IFN-gamma gene expression.
abstract: Interleukin 12 (IL-12) is a heterodimer comprising p35 and p40 subunits which are encoded and regulated separately. The authors previously demonstrated deficient IL-12 production in SLE which correlates negatively with disease activity. The present study was designed to determine whether deficiency of IL-12 and excess production of IL-10 and IL-6 in systemic lupus erythematosus (SLE) are due to aberrant regulation at the gene level. Using semiquantitative RT-PCR assay, it was shown that constitutive expression of IL-12 p35 gene is somewhat impaired in SLE compared with controls and that IL-12 p40 mRNA, which was present at low levels in controls, was undetectable in unstimulated SLE peripheral blood mononuclear cells (PBMC). Gene expression of IL-12 p35 and p40 was significantly increased in response to SAC, with significantly lower SAC-induced expression of p40 in SLE patients than controls. SAC-stimulated IL-12 p35 and p40 mRNAs were significantly augmented by interferon gamma (IFN-gamma). Exogenous IL-12 or IFN-gamma significantly inhibited IL-10 gene expression, without affecting IL-6 mRNA or other proinflammatory cytokine mRNA levels. These observations were further confirmed by studies of protein production at the single cell level using ELISPOT assay. Downregulation of IL-12 p40 expression appears to be the cause of IL12 p70 deficiency in SLE. If this defect could be repaired, normalization of IL-12 and IFN-gamma production should reduce excessive IL-10 and prevent pathology.
authors.affiliation: Department of Pathology, University of Hong Kong, Hong Kong, People's Republic of China.
authors.forename: T F
authors.initials: TF
authors.lastname: Liu
authors.forename: B M
authors.initials: BM
authors.lastname: Jones
authors.forename: R W
authors.initials: RW
authors.lastname: Wong
authors.forename: G
authors.initials: G
authors.lastname: Srivastava
mesh_terms: D002478:Cells, Cultured; D019281:Dimerization; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007371:Interferon-gamma / Q000032:analysis / Q000235:genetics* / Q000494:pharmacology; D016753:Interleukin-10 / Q000032:analysis / Q000235:genetics*; D018664:Interleukin-12 / Q000032:analysis / Q000737:chemistry / Q000235:genetics* / Q000494:pharmacology; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D008180:Lupus Erythematosus, Systemic / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000473:pathology; D008970:Molecular Weight; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013211:Staphylococcus aureus / Q000276:immunology
chemical_list: D012333:RNA, Messenger; D016753:Interleukin-10; D018664:Interleukin-12; D007371:Interferon-gamma