Paola Facchetti

Expression and function of IL-12 and IL-18 receptors on human tonsillar B cells.

IL-12 activates murine and human B cells, but little information is available as to the expression and function of IL-12R on human B lymphocytes. Here we show that the latter cells, freshly isolated from human tonsils, expressed the transcripts of both β1 and β2 chains of IL-12R and that β2 chain mRNA was selectively increased (4- to 5-fold) by incubation with Staphylococcus aureus Cowan I bacteria or IL-12. B cell stimulation with IL-12 induced de novo expression of the transcripts of the two chains of IL-18R, i.e., IL-1 receptor-related protein and accessory protein-like. Functional studies showed that both IL-12 and IL-18 signaled to B cells through the NF-κB pathway. In the case of IL-12, no involvement of STAT transcription factors, and in particular of STAT-4, was detected. c-rel and p50 were identified as the members of NF-κB family involved in IL-12-mediated signal transduction to B cells. IL-12 and IL-18 synergized in the induction of IFN-γ production by tonsillar B cells, but not in the stimulation of B cell differentiation, although either cytokine promoted IgM secretion in culture supernatants. Finally, naive but not germinal center or memory, tonsillar B cells were identified as the exclusive IL-12 targets in terms of induction of NF-κB activation and of IFN-γ production.

T Cell Clones Raised from Chronically Infected Healthy Humans by Stimulation with Toxoplasma gondii Excretory-Secretory Antigens Cross-React with Live Tachyzoites: Characterization of the Fine Antigenic Specificity of the Clones and Implications for Vaccine Development

Excreted-secreted Ags (ESA) of Toxoplasma gondii (Tg) play an important role in the stimulation of the host immune system in both acute and chronic infections. To identify the parasite Ag(s) involved in the maintenance of T cell-mediated long term immunity, 40 ESA-specific T cell clones were derived from three chronically infected healthy subjects. All the clones were CD4+ and recognized both ESA and live tachyzoites in a HLA-DR-restricted manner. Conversely, CD4+ tachyzoite-specific T cell clones from the same subjects proliferated in response to ESA, pointing to shared immunodominant Ags between ESA and Tg tachyzoites. By T cell blot analysis using SDS-PAGE-fractionated parasite extracts, the following patterns of reactivity were detected. Of 25 clones, 6 recognized Tg fractions in the 24- to 28-kDa range and proliferated to purified GRA2, 5 reacted with Tg fractions in the 30- to 33-kDa range; and 4 of them proved to be specific for rSAg1. Although surface Ag (SAg1) is not a member of ESA, small amounts of this protein were present in ESA preparation by Western blot. Of 25 clones, 8 responded to Tg fractions in the 50- to 60-kDa range but not to the 55-kDa recombinant rhoptries-2 parasite Ag, and 6 did not react with any Tg fraction but proliferated in response to either ESA or total parasite extracts. In conclusion, CD4+ T cells specific for either ESA (GRA2) or SAg1 may be involved in the maintenance of long term immunity to Tg in healthy chronically infected individuals.

Serum p55 and p75 tumour necrosis factor receptors as markers of disease activity in juvenile chronic arthritis.

OBJECTIVE: To determine the expression of tumour necrosis factor alpha (TNF alpha) and its soluble receptors (p55 and p75) in the sera and synovial fluid of patients with juvenile chronic arthritis (JCA), and their correlation with disease activity parameters. METHODS: Ninety eight sera from 45 patients with JCA (14 systemic, 12 polyarticular, 19 pauciarticular), 20 sera from age matched healthy controls, and five synovial fluids from five antinuclear antibody (ANA) positive pauciarticular JCA patients were tested for the presence of TNF alpha, soluble TNF receptors p55 and p75 (sTNFRp55, sTNFRp75), and interleukin-6 (IL-6) by an enzyme amplified sensitivity immunoassay. Physician global estimate of disease activity, weekly fever score and joint score, C reactive protein (CRP), erythrocyte sedimentation rate (ESR), and haemoglobin concentration were evaluated as parameters of disease activity. The expression of p55 and p75 on peripheral mononuclear cells (MNCs) from five patients with systemic JCA and synovial MNCs from five ANA positive patients with pauciarticular JCA was evaluated by flow cytometry. RESULTS: TNF alpha serum concentrations did not differ significantly between the patients with active JCA and the control group. No correlation was found between TNF alpha and parameters of disease activity, but both p55 and p75 showed a significant positive correlation with the physician global estimate of disease activity (p < 0.001), ESR (p < 0.001), CRP (p < 0.001), and serum concentrations of IL-6 (p < 0.001). Serum concentrations of haemoglobin correlated inversely with the concentrations of p55 and p75 (p < 0.001). Synovial lymphocytes selectively expressed the p75 surface receptor. CONCLUSIONS: sTNFRp55 and sTNFRp75 each represent a sensitive marker of disease activity in JCA. Their increased expression in biological fluids may support the hypothesis that TNF alpha has a role in the pathogenesis of JCA.

Functional and molecular characterization of tumour-infiltrating lymphocytes and clones thereof from a major-histocompatibility-complex-negative human tumour: Neuroblastoma

Abstract Neuroblastoma (NB) is a major-histocompatibility-complex(MHC)-negative neuroectodermal tumour that is often infiltrated with lymphocytes. A detailed characterization of NB-associated tumour-infiltrating lymphocytes (TIL) has never been carried out. Here we have investigated the immunophenotype and the cytotoxic activities of TIL from nine and seven NB patients respectively. Furthermore, the T cell receptor (TcR) variability and the patterns of cytokine gene expression of fresh versus recombinant (r) interleukin(IL)-2-cultured TIL were studied in four NB cases. The results obtained showed the following: (1) freshly isolated TIL were comprised of a mixture of CD4+ and CD8+ T cells partially expressing HLA-DR and/or CD25. The CD4/CD8 ratio ranged from 0.5 to 5 in the different cases. Upon culture of TIL with rIL-2, an increased proportion of CD56+ and CD8+ lymphocytes was consistently observed; (2) IL-2-expanded TIL lysed natural-killer(NK)-sensitive and lymphokine-activated-killer (LAK)-sensitive target cell lines; (3) reverse-transcriptase/polymerase-chain-reaction (RT-PCR) experiments showed that most TcR Vβ genes were expressed both in fresh and in cultured TIL, suggesting that such cell populations were polyclonal; (4) interferon γ, IL-4, IL-5, tumour necrosis factor (TNF) α, IL-8, IL-10 mRNA and, to a lesser extent, IL-2 mRNA were expressed by cultured TIL, as assessed by RT-PCR; the corresponding tumour samples consistently contained TNFα, IL-8 and IL-10 mRNA, whereas IL-2 and IFNγ mRNA were faintly expressed in some NB tumors and IL-4 and IL-5 mRNA were never detected. A total of 90 clones were subsequently raised from IL-2-expanded TIL from six NB patients; 87/90 clones were of T cell lineage with a CD4+ or CD8+ immunophenotype, whereas the 3 remaining clones were of NK cell origin. Upon triggering of the CD3-TcR complex, 64% CD4+ and 77% CD8+ T cell clones killed the murine P815 mastocytoma cell line. Virtually no T cell clone lysed a LAK-sensitive NB cell line, whereas 15% CD4+ and 17% CD8+ clones mediated NK-like activity against the K562 cell line. Finally, the patterns of cytokine production by CD4+ clones were roughly consistent with those of a T helper (Th)1 profile and similar to those observed in CD8+ clones.

Engrafted maternal T cells in human severe combined immunodeficiency: Evidence for a T H2 phenotype and a potential role of apoptosis on the restriction of T-cell receptor variable β repertoire

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Clonal analysis of peripheral blood lymphocytes from three patients with advanced neuroblastoma receiving recombinant interleukin-2 and interferon α

In this study we have investigated, at the population and the clonal levels, the immunophenotypes and the non-specific cytotoxic functions of peripheral blood lymphocytes from three stage IV neuroblastoma patients receiving treatment with recombinant interleukin-2 (IL-2) and interferon α (IFNα). Both IL-2 alone and the combination of IL-2 and IFNα caused an in vivo expansion of CD56+, CD3− NK cells most of which expressed the p75 molecule, i.e. the β chain of the IL-2 receptor. Peripheral blood mononuclear cells (PBMC), drawn after treatment, displayed an increased NK activity, but no lymphokine-activated killer (LAK) activity. However, the subsequent in vitro culture of PBMC with high-dose IL-2 induced the generation of a potent LAK activity, which was mediated by an expanded population of CD3+ CD8+ T cells. Finally lymphocytes that had been isolated after cytokine therapy were cloned, in the presence of low-dose phytohemagglutin, immediately or following culture with IL-2. Clones derived from LAK cells expanded in vitro had predominantly a CD3+, CD8+ immunophenotype, whereas those raised from freshly separated lymphocytes were either CD3+, CD4+ or CD3+, CD8+ in equal proportions. Most of the above clones were poorly or not at all cytolytic against NK-sensitive or NK-resistant targets. In contrast, the few NK clones obtained (CD3−, CD56+) lysed all targets with high efficiency.