Cell type-specific signaling in response to interferon-gamma.

Type II interferon-gamma (IFN-gamma) is a pleiotropic cytokine that regulates many different cellular functions. The major signaling pathway activated by IFN-gamma involves sequential phosphorylation of the tyrosine residues of the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) proteins, providing the primary mechanism through which gene expression is induced. However, recent work has revealed that the responses are complex, as shown by the activation of kinases in addition to JAKs, differential patterns of activation of STAT1, STAT3, and STAT5 in different cells, and activation of transcription factors other than STATs. This complexity is used to regulate biological functions differentially in a cell type-specific manner, by activating different specific signals and patterns of gene expression.

Cytokine and IL-12 receptor mRNA discriminate between different clinical subtypes in multiple sclerosis.

Little is known about the involvement of cytokines in the pathogenesis of primary progressive (PP) multiple sclerosis (MS). We evaluated in this cross-sectional study whether IL-18, IL-12p35, IL-12p40, TNF-alpha, IFN-gamma, IL-10, IL-4, TGF-beta, IL-12Rbeta1, and IL-12Rbeta2 mRNA expression in unstimulated white blood cells showed significant differences between relapsing-remitting (RR), secondary progressive (SP) and PP MS patients, and healthy controls. All clinical subtypes showed unique mRNA expression patterns as compared to the controls. Both RR and SP patients displayed increased levels of IL-12p40, IL-18, and TGF-beta mRNA compared to controls, whereas PP patients showed only increased IL-18 mRNA levels. Both in PP and SP patients, IFN-gamma and IL-10 mRNA were decreased compared to RR patients and controls. PP patients were unique in that they showed decreased IL-12Rbeta1 mRNA. In conclusion, our data show that the assessment of cytokine (receptor) mRNA profiles is useful to discriminate between the different clinical subtypes and suggest that different cytokines are involved in the pathogenesis of PP MS as compared to RR and SP MS.

Interferon-beta in multiple sclerosis: altering the balance of interleukin-12 and interleukin-10?

Interferon-beta is a remarkably pleiotropic molecule. Antiviral, pro- and antiproliferative, pro- and antiapoptotic, and complex immunoregulatory activities have all been described. The precise mechanism(s) that underlie the beneficial effects of interferon-beta in multiple sclerosis remain poorly understood; this has hindered progress in the search for more effective therapies. An increasing body of literature supports the hypothesis that interferon-beta-mediated changes in the production and activities of the immunoregulatory cytokines interleukin-12 and interleukin-10 are important to the therapeutic benefits of interferon-beta in multiple sclerosis. These data are reviewed here.

Contrasting responses to interferon beta-1b treatment in relapsing-remitting multiple sclerosis: does baseline interleukin-12p35 messenger RNA predict the efficacy of treatment?

Interferon (IFN)-beta treatment is effective in relapsing-remitting multiple sclerosis (RR-MS) via an as yet unidentified mechanism. In the present study, we investigated whether the expression of messenger RNA (mRNA) encoding the interleukin (IL)-12 subunits p40 and p35, IL-12 receptor chains, IL-18, tumor necrosis factor-alpha (TNFalpha), IFNgamma, IL-10, IL-4, or transforming growth factor-beta in unstimulated whole blood of 26 RR-MS patients changed during 6 months of IFNbeta-1b treatment. In these patients, a significant change was found in TNFalpha mRNA, whereas changes in IL-12 receptor-beta2 and IL-10 mRNA showed a trend. IFNbeta-1b-related changes in cytokine mRNA expression were next evaluated in clinical subgroups of RR-MS patients classified as either clinical responders or nonresponders on the basis of Expanded Disability Status Scale progression and the number of relapses and steroid interventions needed in the 2 years before initiation of treatment compared with the 2 years after initiation of treatment. These subgroups showed different response patterns to IFNbeta-1b treatment with respect to IL-10, TNFalpha, and IL-18 only. Surprisingly, clinical responders displayed no change in these cytokines, whereas nonresponders showed a decrease in TNFalpha and IL-18 mRNA as well as a transient increase in IL-10 mRNA. Baseline levels of IL-12p35 mRNA were lower in the responders compared with the nonresponders: this marker correctly predicted the clinical outcome in 81% of the 26 patients under investigation.

Decreased interleukin-10 and increased interleukin-12p40 mRNA are associated with disease activity and characterize different disease stages in multiple sclerosis.

It has been shown that proinflammatory and antiinflammatory cytokines correlate with disease activity in multiple sclerosis (MS). To establish whether such correlations depend on the disease stage, we assessed in a longitudinal fashion the expression of interleukin (IL)-12 (p40 and p35), tumor necrosis factor-alpha, interferon-gamma, and IL-10 mRNA by competitive polymerase chain reaction in unstimulated peripheral blood mononuclear cells of relapsing-remitting (RR) and secondary progressive (SP) MS patients, in relation to monthly clinical and magnetic resonance imaging monitoring. MS patients had increased levels of IL-12p40 and decreased levels of IL-10 mRNA compared with controls; this difference was most pronounced in SP patients. Both RR and SP patients had increased levels of IL-12p40 mRNA compared with controls during the development of active lesions. Moreover, in RR MS an increase was found before relapse. IL-12p35 mRNA was decreased in both groups, and in relation to disease activity it showed a pattern different from IL-12p40 mRNA. In RR MS, IL-10 mRNA was low 4 weeks before magnetic resonance imaging activity and 6 weeks before relapse; a significant increase to normal levels was noted when active lesions became apparent. In contrast, SP patients showed low IL-10 mRNA levels constitutively, suggesting that IL-10 plays an important role in the control of disease progression.

Differential regulation of interleukin-10 (IL-10) and IL-12 by glucocorticoids in vitro.

Antigen-presenting cells are thought to modulate the development of Th1 and Th2 cells by the secretion of interleukin-10 (IL-10) and IL-12. Because glucocorticoids (GC) favor the development of Th2 responses, we determined whether dexamethasone (DEX) and hydrocortisone (HC) have differential effects on lipopolysaccharide-induced IL-10 and IL-12 production in whole-blood cultures. Significant inhibition of IL-12(p40) and IL-12(p70) was found with 10(-8) mol/L and 10(-9) mol/L DEX respectively, whereas IL-10 was relatively insensitive or even stimulated. Accordingly, the expression of IL-12(p40) and IL-12(p35) mRNA was more sensitive to DEX than IL-10 mRNA. The glucocorticoid receptor (GR) antagonist RU486 enhanced IL-12 production and largely abrogated the inhibition of IL-12 by GC, indicating that this suppression was mainly GR-mediated. High concentrations of RU486 were inhibitory for IL-10, suggesting that GC may exert a positive effect on IL-10. In the presence of neutralizing anti-IL-10 antibodies, DEX was still capable of IL-12 suppression whereas RU486 still enhanced IL-12 production, indicating that GC do not modulate IL-12 via IL-10 exclusively. Taken together these results indicate that GC may favor Th2 development by differential regulation of IL-10 and IL-12.

Human T cell repertoire generation in the absence of MHC class II expression results in a circulating CD4+CD8- population with altered physicochemical properties of complementarity-determining region 3.

In this study, we have investigated the impact of deficient MHC class II expression on the use of TCRBV6 and TCRBJ gene elements, and on the pattern of amino acid incorporation exhibited in the N1-D-N2 segments of the third complementarity-determining region (CDR3) of these TCRBV6 rearrangements. To this end, we have analyzed circulating T cells from three, nonrelated MHC class II-deficient (bare lymphocyte syndrome (BLS)) patients and three MHC class II-expressing family members. The patients and healthy controls exhibited similar, nonrandom usage profiles of TCRBV6 and TCRBJ gene elements in both the CD4+CD8- and the CD4-CD8+ subsets of peripheral blood T cells. No statistically significant differences between patients and controls were detected in the length of CDR3, or in the amount of non-germline modification at the sites of recombination. However, detailed analysis of the TCRBV6 rearrangements derived from the CD4+CD8- subsets from the BLS patients revealed patterns of amino acid incorporation into the N1-D-N2 region of CDR3 that resulted in altered charge and hydropathicity properties of the presumed Ag binding site. In this way, we have been able to demonstrate that human T cell repertoire development in the absence of MHC class II expression results in a circulating CD4+CD8- T cell population bearing TCRs with altered CDR3 profiles. Such altered profiles are likely to be a direct reflection of the lack of MHC class II-mediated selection processes in these BLS patients.

Definition of a novel complementation group in MHC class II deficiency.

In this study we analyzed fibroblasts derived from an MHC class II deficiency patient (type III bare lymphocyte syndrome). Northern blot analysis showed that upon induction with IFN-gamma these fibroblasts did not express HLA class II genes and displayed a strongly reduced level of HLA class I gene expression when compared with fibroblasts of a healthy individual. However, when analyzed by RT-polymerase chain reaction (PCR), residual expression could be detected for HLA-DRA, DPB, and DQA, but not for HLA-DRB, DPA, and DQB. The lack of HLA-DRB transcripts in the patient fibroblasts and the high degree of sequence polymorphism of HLA-DRB were exploited in the further analysis of these fibroblasts. Thus far, at least three, and probably four, complementation groups have been defined among patient-derived and experimentally-derived MHC class II-negative cell lines. Transient heterokaryons between the patient fibroblasts and representative B-lymphoblastoid cell lines from each of the complementation groups were analyzed by RT-PCR and Southern blotting, using HLA-DRB-specific primers and biotin-labeled sequence specific oligonucleotides, respectively. These analyses showed that the fibroblasts of this particular patient belonged to a novel complementation group in MHC class II deficiency.