Mikio Oka

Role of L3T4+ and Lyt-2+ T Cell Subsets in Protective Immune Responses of Mice against Infection with a Low or High Virulent Strain of Toxoplasma gondii

In order to elucidate the role of T cell subsets in protective immunity against infection with high virulent and low virulent strains of Toxoplasma gondii, monoclonal antibodies specific for T cell subsets were injected into mice before immunization or challenge infection. Treatment of mice with monoclonal antibody to either L3T4+ or Lyt‐2+ T cells before they were immunized with Toxoplasma cell homogenate prepared from high virulent RH strain tachyzoites markedly reduced survival after mice were challenged with low virulent bradyzoites of the Beverley strain. Thus, induction of protective immunity against bradyzoites of the Beverley strain requires the presence of both L3T4+ and Lyt‐2+ T cells. In contrast, mice injected with living bradyzoites of the low virulent Beverley strain after immunization with Toxoplasma cell homogenate acquired protective immunity against high virulent tachyzoites of the RH strain. Lyt‐2+ T cells alone appear to be final effector cells for protection against the challenge with high virulent RH strain tachyzoites, since treatment of the bradyzoite‐immune mice with anti‐Lyt‐2 antibody, but not anti‐L3T4 antibody, before challenge significantly increased mortality.

Combined treatment of autoimmune MRL/MP-lpr/lpr mice with a herbal medicine, Ren-shen-yang-rong-tang (Japanese name: Ninjin-Youei-To) plus suboptimal dosage of prednisolone

Therapeutic effects of combined treatment with a Chinese medicine prescription, Ren-shen-yang-rong-tang (Japanese name: Ninjin-youei-to, NYT) and suboptimal doses of prednisolone (PSL) on pathological findings of autoimmune-prone MRL/lpr mice were examined. Six-week-old MRL/lpr mice were treated orally with 1000 mg/kg of NYT, 0.5 or 2 mg/kg of PSL, 1000 mg/kg of NYT plus 0.5 or 2 mg/kg of PSL (combined treatment) or solvent only (control) six times per week. The rates of signs and symptoms of autoimmune disease (lymphadenopathy, proteinuria, dermatitis, loss of hair) were suppressed significantly in groups given PSL (2 mg/kg) alone, NYT alone and combined treatment with PSL (2 mg/kg) plus NYT (1000 mg/kg) compared with control, respectively, whereas treatment with PSL (0.5 mg/kg) alone did not inhibit their occurrence. ConA response and IL-2 production were also improved significantly in lymphocytes of mice given the combined treatment. Interestingly, treatment with NYT alone enhanced further the augmented IFN-gamma production in MRL/lpr mice but the combined treatment suppressed such an augmented production. The combined treatment dramatically reduced the level of anti-DNA antibodies in serum of MRL/lpr mice. By contrast, NYT alone treatment had no effect on autoantibodies production. These results suggest that combined treatment with NYT plus a suboptimal dose of PSL could be effective for systemic lupus erythematosus without severe side-effects.

Treatment effect of a traditional Chinese medicine, Ren-shen-yang-rong-tang (Japanese name: Ninjin-Youeito), on autoimmune MRL/MP-lpr/lpr mice

Abstract Autoimmune MRL /lpr mice were i.p. treated with 200 mg/kg Ren-shen-yang-rong-tang (Japanese name: Ninjin-youei-to, NYT), a traditional Chinese herbal medicine (Japanese name: Kampo), from 8 weeks of age every 3 days before the onset of autoimmune disease. Compared to age-matched control MRL /lpr mice, the serum IL-6 concentration in NYT-treated mice was decreased, their serum IFN-γ concentration was increased, and the proliferative responses of whole and enriched CD4 + cells in their spleen and lymph nodes stimulated with ConA in vitro were restored. FACS analysis revealed that the rate of decreased CD4 + CD8 + T-cell population in the thymus was decreased in MRL /lpr mice but recovered by NYT treatment. Further, adult thymectomized (ATX) MRL /lpr mice were treated with 200 mg/kg NYT similarly. NYT treatment prolonged the survival of sham-operated MRL /lpr mice and ameliorated their proteinuria but did not improve such autoimmune manifestations in ATX-MRL /Ipr mice. These findings suggest that NYT plays an important role in the abrogation of autoimmune-prone T cell differentiation and that the therapeutic effect of NYT is dependent on the thymus in MRL /Ipr mice.

An extract of seeds fromAeginetia indica L., a parasitic plant, induces potent antigen-specific antitumor immunity in Meth A-bearing BALB/c mice

SummaryThe antitumor activity of an extract of seeds fromAeginetia indica L., a parasitic plant, was investigated. BALB/c mice, inoculated i.p. 1 × 105 syngeneic Meth A tumor cells, were administered 2.5 mg/kgA. indica extract i.p. every 2 days from day 0. The untreated mice died of an ascitic form of tumor growth within 21 days, whereas all the treated mice completely recovered from tumor challenge without any side-effects. The extract did not exert direct cytotoxic activity against Meth A in vitro. Mice that survived after the first challenge as a result ofA. indica treatment overcame the rechallenge with homologous Meth A without additional administration of the extract. On the other hand, those mice could not survive after rechallenge with Meth 1 tumor cells, which were also established in BALB/c mice but were different in antigenicity from Meth A, suggesting the development of antigen-specific concomitant immunity in theA. indica-cured mice. In the induction phase of antitumor resistance in this system, CD4+ T cells appeared to be the main contributors, since in vivo administration of anti-CD4 mAb completely abolished such resistance. In contrast, anti-CD8 mAb administration did not influence the effect ofA. indica. The importance of CD4+ T cells in antitumor immunity was again clarified by Winn assay; that is, spleen and lymph node cells depleted of CD4+ T cells in vitro prior to assay abolished antitumor activity on co-grafted Meth A tumor cells in vivo.

Polyclonal B-cell stimulative and immunosuppressive activities at different developmental stages of Trypanosoma gambiense.

Bloodstream trypomastigote and cultured procyclic (insect midgut) forms of a monomophic strain of Trypanosoma gambiense were tested for their abilities to induce polyclonal B‐cell activation (PBA) and immunosuppression (IS) in mice. Injection of a cell homogenate of bloodstream trypomastigotes induced both PBA and IS, while neither PBA nor IS was observed in mice injected with a cell homogenate of cultured procyclics. The results indicate that the substance(s) inducing PBA or IS is related to the developmental stage of the parasites.

Trypanosoma gambiense: Immunosuppression and polyclonal B-cell activation in mice

The relationship between the suppression of antibody response and polyclonal B-cell activation was studied in mice treated with a cell homogenate of Trypanosoma gambiense. The cell homogenate injection in mice caused a progressive increase in splenic background plaque-forming cell response to sheep erythrocyte. In the mice with markedly increased background plaque-forming cell response, the different reactivity in the primary antibody response to sheep erythrocytes was observed between the intraperitoneal and intravenous immunization with sheep erythrocytes. The intraperitoneal immunization of mice with sheep erythrocytes strongly suppressed the antibody response, while the intravenous immunization with sheep erythrocytes led to an enhancement of the antibody response. The intraperitoneal injection of silica particles, a toxic agent to macrophages, 30 min before intraperitoneal immunization with sheep erythrocytes abolished the suppression of the antibody response completely. In addition, restoration of the suppressed antibody response was found in mice immunized intraperitoneally with a high dose of sheep erythrocytes. It appears that the suppression of antibody response is not attributable to polyclonal B-cell activation, and is associated with the elevation of the phagocytic activity of peritoneal macrophages.

Agglutination Antibody Responses to Trypanosoma gambiense Homogenate in Mice Treated with Dextran Sulfate 500 and Carrageenan

Dextran sulfate 500 and carrageenan, sulfated polysaccharides, have been considered as macrophage-toxic giving profound effects on the immune response. This work deals with agglutination antibody responses to T. gambiense homogenate in mice treated with dextran sulfate 500 and carrageenan. Antibody responses to the first immunization were suppressed in mice treated with the agents before the first immunization but reverse was the case with the response to the second immunization. These suppression and enhancement appeared to be dependent on the timing of treatment in regard to the time of the first immunization. The enhanced antibody response was abolished by either treating the mice with anti-thymocyte serum or transferring of spleen cells treated with anti-thymocyte serum into mice. Thus, the enhancement of antibody response is seemingly attributable for the most part to potent memory T cells induced by treatment with the agents.

In situ microfluorometry of kinetoplast and nuclear DNAs in Trypanosoma gambiense unusual repairment of DNA after treatment with bleomycin

The blood stream form of Trypanosoma gambiense was smeared on a nonfluorescent slide glass with 1 microgram/ml of Hoechst 33258 in 1 mM Tris-HCl buffer (pH 7.2) containing 1% 2-mercaptoethanol and subjected to the in situ microfluorometry. Effects of bleomycin (BL) on the kinetoplast (K)-DNA and nuclear (N)-DNA of T. gambiense were examined in the time course to 6 h after injection of BL into the infected mice. An enhancement of fluorescence occurred 30 min after the injection and then slowed down. This enhancement was due to DNA synthesis both in the K-DNA and N-DNA. This suggests that the strong repairment occurs in both DNAs after treatment with BL.