T. Onodera

Interferon-γ plays a role in pancreatic islet-cell destruction of reovirus type 2 -induced diabetes–like syndrome in DBA/1 suckling mice

Reovirus type 2 (Reo‐2) infection in DBA/1 suckling mice causes insulitis, which leads to pancreatic islet‐cell destruction,resulting in a diabetes–like syndrome. T‐helper (Th)1 cytokines are thought to play a key role in islet inflammation in insulin‐dependent diabetes mellitus. We examined this hypothesis in the Reo‐2‐induced diabetes–like syndrome. We used reverse transcriptase polymerase chain reaction (PCR) and quantitative PCR techniques to examine mRNA expression of interferon (IFN)‐γ (Th1 type cytokine), and interleukin (IL)‐4 (Th2 type cytokine) in splenic cells. We observed that in Reo‐2 infected mice the level of IFN‐γ expression increases with the development of insulitis, whereas expression of message for IL‐4 is minimal to detectable with the immuno‐inflammatory process 10 days after infection. The treatment of monoclonal antibody (mAb) against mouse IFN‐γ during the expansion phase of insulitis (5–9 days after infection) inhibited the development of insulitis and the elevation of blood glucose concentrations in a dose dependent manner. Furthermore altered CD4+/CD8+ cell ratio compared with uninfected mice in the splenic cells by the infection was recovered to the ratio of uninfected mice by the treatment of mAb against mouse IFN‐γ, suggesting normalization of T cell balance in immune system. These results suggest that Reo‐2‐triggered autoimmune insulitis may be mediated by Th1 lymphocytes and IFN‐γ may play a role in islet inflammation leading to islet cell destruction.

Possible Involvement of IL‐12 in Reovirus Type‐2‐Induced Diabetes in Newborn DBA/1 Mice

This study extends our previous observations that the reovirus type‐2(Reo‐2) can induce autoimmune insulitis, which may be mediated by T‐helper(Th)1‐dependent mechanisms, resulting in diabetes in newborn DBA/1 mice. In this study mRNA expression for Th1‐related cytokines including Th1 and Th2 cytokines in splenic cells was examined by reverse transcriptase polymerase chain reaction (RT–PCR) in relation to the development of insulitis. Furthermore, the effect of monoclonal antibody (MoAb) against interleukin (IL)‐12(p40) on the development of insulitis and the mRNA expression in the splenic cells was examined. The mRNA expression for IL‐12(p40), IL‐18, and interferon (IFN)‐γ, but not IL‐5, increased in the spleen in parallel with the development of insulitis. The treatment with MoAb to IL‐12(p40) reduced the insulitis with diabetes which was associated with a decrease in the mRNA expression for IL‐12(p40), IL‐18 and IFN‐γ, and an increase of IL‐4 mRNA expression in the spleen. The present study suggested that Th1‐dominant systemic immune responses, being responsible for the development of autoimmune insulitis, might be induced by IL‐12‐induced and IL‐18‐activated mechanisms.

Decrease in neutrophil migration induced by endotoxin and suppression of interleukin-1 production by macrophages in lactic dehydrogenase virus-infected mice.

Neutrophil (PMN) migration into the peritoneal cavity after intraperitoneal injection of lipopolysaccharide (LPS), chemotactic activity of PMN, interleukin-1 (IL-1) production by macrophages (M phi) and its ability to attract PMN in mice chronically infected with lactic dehydrogenase virus (LDV) were compared with those in uninfected control mice. PMN migration into the peritoneal cavity decreased in infected mice when LPS was injected intraperitoneally. PMN chemotactic activity did not show any difference following infection. To assess the mechanism of this decreased PMN migration, IL-1 production, which is responsible for PMN attraction, was studied in LDV-infected mice. IL-1 production by M phi derived from infected mice decreased and its ability to attract PMN was weak. IL-1 production by M phi from control and infected mice increased after treatment by indomethacin and LPS. PMN migration into the peritoneal cavity increased after treatment with indomethacin and LPS in both control and infected mice. However, the rate of increase of IL-1 production and PMN migration was greater in infected mice. These results suggest that the excess activation of cyclo-oxygenase-derived products (prostaglandins) in infected mice might be responsible for the suppression of IL-1 production by M phi, resulting in decreased PMN migration induced by endotoxin.

CpG oligodeoxynucleotides accelerate reovirus type 2-triggered insulitis in DBA/1 suckling mice

We reported previously that reovirus type‐2 (Reo‐2) triggers T‐helper (Th) 1‐mediated autoimmune insulitis resulting in temporal impaired glucose tolerance (IGT) approximately 10 days post infection (d.p.i) in suckling DBA/1 mice. We hypothesized that CpG motifs in bacteria may enhance virus‐induced insulitis through its content of unmethylated CpG motifs. In the infected mice, the intraperitoneal treatment of synthetic 20‐base oligodeoxynucleotides with CpG motifs (CpG ODN) caused increase in cumulative incidence of insulitis with IGT, increased serum interferon (IFN)‐γ concentration, and high frequency of autoantibody against pancreatic islet cells, compared to the infected mice without CpG ODN at 17 d.p.i. Also CD4+ and CD8+ lymphocytes infiltrated in and/or around pancreatic islets in the CpG ODN‐treated mice. This evidence suggests that CpG ODN may contribute to accelerate Reo‐2‐induced autoimmune reaction against pancreatic islet cells via additional effects of Th1 cytokines especially IFN‐γ.

Increased superoxide anion release by peritoneal macrophages in mice with a chronic infection of lactic dehydrogenase virus.

The function of macrophages in mice chronically infected by lactic dehydrogenase virus (LDV) was studied. Superoxide anion (O2-) release was examined by using peritoneal macrophages. O2- release increased markedly from 3 weeks to 12 months, but not at 1 week post infection. O2- release was 1.2 to 1.5 times greater than in uninfected mice. Increased O2- release from macrophages in LDV-infected mice may explain, at least in part, suppressive effects on tumour growth seen in the chronic phase of infection.

Macrophage function in the acute phase of lactic dehydrogenase virus-infection of mice: Suppression of superoxide anion production in normal mouse peritoneal macrophages by interferon-α in vitro

The effect of interferon (IFN)-alpha on the release of superoxide anions (O2-) by normal mouse macrophages (PEM) was examined. Sera from LDV-infected mice at 1 day, but not at 7 days post-infection, suppressed the O2- release by PEM. When PEM were exposed in vitro for 24 h to IFN-alpha, their capacity to release O2- was significantly suppressed. Progressive suppression of O2- release with increasing IFN-alpha concentration was observed. These results suggest that IFN-alpha in the circulation may be one of several suppressive factors on macrophage function in the early phase of infection and IFN-alpha may play a modulatory role in inflammation and immunity.

Inhibition of contact sensitivity by interferon in mice infected with lactic dehydrogenase virus.

The effect of acute lactic dehydrogenase virus (LDV) infection was studied with respect to contact sensitivity (CS) to 2,4-dinitrofluorobenzene (DNFB). CS reaction was severely inhibited in the acute phase but not in the chronic phase of infection. The role of interferon (IFN) was studied to understand further the inhibition of CS during LDV infection. IFN in the blood was detected only in the acute phase, but not in the chronic phase of infection. When anti-IFN (alpha/beta) was administered to infected mice, no inhibition of CS was seen. CS was inhibited in uninfected mice treated with IFN (alpha/beta). These results suggest that IFN production in the blood may be responsible, at least in part, for inhibition of CS observed in the acute phase of LDV infection.

Detection of the Binding of IgG2a and IgG2b on the Surface of Macrophages from Mice Chronically Infected with Lactic Dehydrogenase Virus

This study showed that sera from mice chronically infected with lactic dehydrogenase virus (LDV) contained virus-antibody complexes (IC). IgG2a and IgG2b, but not IgG1, IgG3, IgM or IgA, were demonstrated on the surface of macrophages from chronically infected mice. These results suggest that IC in the circulation may bind to Fc receptors for IgG2a and IgG2b on the surface of macrophages and lead to the modulation of macrophage function seen in chronically LDV-infected mice.