Giorgio Cavallo

Activation of protein kinase C down-regulates IFN-gamma receptors

Treatment of mouse EL-4 cells with intracellular activators of protein kinase C, namely 4-phorbol 12-myristate 13-acetate (PMA) and diacylglycerol, resulted in 90% reduction in cell surface interferon-gamma (IFN-gamma) receptors as judged by iodinated-IFN-gamma binding. This did not seem to be due to a decreased in the receptor affinity, since that of the remaining surface receptors appeared to be significantly increased as shown in Scatchard plot analysis. Kinetics experiments revealed that a PMA treatment as short as 15 min was sufficient to induce a decrease of 30% of IFN-gamma receptors, whereas the highest levels of down-regulation were observed after 60-90 min. Treatment of EL-4 cells with calcium ionophore, A23187, although ineffective by itself, dramatically increased the ability of suboptimal PMA concentrations to mediate IFN-gamma receptor down-regulation. Finally, specificity studies revealed that PMA is particularly effective in decreasing the binding of IFN-gamma to T-lymphocytes. Altogether these results suggest a possible involvement of protein kinase C in the regulation of IFN-gamma receptor expression.

Cell reactivity towards syngeneic neoplastic cells in mice hypersensitized to dinitrophenol

Abstract Three groups of 12-week old inbred Balb/c mice were sensitized by 3 weekly skin paintings with 1-fluoro-2,4-dinitrobenzene. One week later, one group and a further unsensitized group were inoculated with a non-inducing dose of adenocarcinoma (ADK-lt) cells coated with dinitrophenol, one group received an identical dose of uncoated tumor cells and the third sensitized group was not treated. After 15 days, these four groups and a further untreated group were challenged with 5 × 105 ADK-lt cells. During the following three weeks, the presensitized and prime group displayed delayed tumor appearance and slower tumor growth. Extensive necrosis and massive parvicellular infiltration were noted in 80% of tumors from animals in this group.

Is antibody-dependent cellular cytotoxicity an important mechanism of resistance to tumors in vivo?

Abstract The ability of heterologous antibody toward tumor membrane antigens to suppress the growth of a spontaneous adenocarcinoma in tolerant adult and newborn mice was investigated. Preinoculation of specific antibody strongly enhanced the resistance of 12-week-old mice to subsequent tumor challenge. The antibody activity was specific since an unrelated tumor was not affected. It was also age-dependent, since newborn mice were not protected. The mechanisms involved in the suppression of this tumor in vivo are discussed.

La rispostain vivo alľinterleron-α/β

(IFN-α/β) fu valutata misurando ľinduzione di alcuni RNA messaggeri (mRNA) IFN-inducibili in topi DBA/2 inoculati con poli I:C. Utilizzando sonde di cDNA. omologhe alľmRNA dei seguenti geni: 202, 2′-5′ oligoadenilatosintetasi (2-5A sintetasi) ed H-2, si e osservato un significativo aumento di mRNA nella milza e nel midollo a 6 ore dalľinoculo intraperitoneo (i.p.) del poli I:C. Gli mRNA raggiungevano il loro massimo livello di espressione tra le 12 e le 24 ore dalľinoculo per poi decrescere gradatamente. Il pretrattamento con anticorpi anti-IFN-α/β di murino riduceva di circa il 60% ľaumento di mRNA. Nel loro insieme questi risultati dimostrano che anchein vivo gli IFN sono in grado di aumentare ľespressione di alcuni geni.Regulation of gene expression in vivoby interferons.In vivo responses to interferon-α/β (IFN-α/β) in mice were determined by measuring the steady-state levels of induced mRNAs following injection of poly I:C. With cDNA probes for mouse 202, 2′-5′ oligoadenylate synthetase and H-2 an increase of the corresponding mRNAs in the spleen and in the bone marrow was observed as early as 6 hours after poly I:C injection. Maximal levels of mRNA expression were reached between 12 and 24 hours after the injection, followed by a gradual decrease. Pretreatment of mice with anti-mouse IFN-α/β significantly impaired mRNA induction by poly I:C. Altogether these results suggest that alsoin vivo IFN-α/β may increase gene expression.Riassunto(IFN-α/β) fu valutata misurando ľinduzione di alcuni RNA messaggeri (mRNA) IFN-inducibili in topi DBA/2 inoculati con poli I:C. Utilizzando sonde di cDNA. omologhe alľmRNA dei seguenti geni: 202, 2′-5′ oligoadenilatosintetasi (2-5A sintetasi) ed H-2, si è osservato un significativo aumento di mRNA nella milza e nel midollo a 6 ore dalľinoculo intraperitoneo (i.p.) del poli I:C. Gli mRNA raggiungevano il loro massimo livello di espressione tra le 12 e le 24 ore dalľinoculo per poi decrescere gradatamente. Il pretrattamento con anticorpi anti-IFN-α/β di murino riduceva di circa il 60% ľaumento di mRNA. Nel loro insieme questi risultati dimostrano che anchein vivo gli IFN sono in grado di aumentare ľespressione di alcuni geni.

Production of Antibodies Against the Murine IFN-γ Receptor

Stimulation of T-lymphocytes with antigens or mitogens triggers the release of several lymphokines, that regulate the immune response (1). Of these, IFN- γ has been shown to control the activity of several cell populations, namely T- and B-lymphocytes, natural killer cells and macrophages (2). The initial IFN-target cell interaction occurs at specific membrane receptors (3). Previous data have demonstrated that the number of binding sites varies from 2,000 to 25,000, with dissociation constants (Kd) between 10-9 and 10-11 (3). One of the major obstacles, however, to characterization and purification of the receptor molecule is that it is expressed in a number of binding sites per single cell insufficient for its purification and biochemical characterization.

Interferon-γ plays a crucial role in T lymphocyte reaction against alloantigens

SummaryIn this study we report that addition to mixed lymphocyte reactions of monoclonal antibodies to interferon-γ inhibits alloantigen recognition and induction of cytotoxic T lymphocytes by inducing early and highly effective suppressor T lymphocytes. This inhibitory activity is not confined toin vitro models, since daily local injection of these antibodies in CBA/J mice blocks the rejection of fully allogeneic tumor cells consistently displayed by untreated CBA/J mcie.