Effects of different allo-Treg/allo-NK ratios on graft-versus-host disease in transplanted mice

To investigate the effects of allo-Treg cells, allo-NK cells, and their mixtures in different proportions on Graft-versus-host disease (GVHD) in bone marrow transplant mouse model. In this study, C57BL/6 mice were used as donors, and 6 Gy dose of 60Co γ was used as the receptor of BALB/c mice. The recipient mice were divided into NC (normal saline), CON (bone marrow cells), NK (bone marrow cells + NK cells), Treg (bone marrow cells + Treg cells), NK+ Treg (1:1) (bone marrow cells +1:1 ratio of Treg cells, NK cells), and NK+ Treg (6:1) (bone marrow cells +1:6 ratio of Treg cells, NK cells), according to the different injection mode through the tail vein. The differences of white blood cell (WBC), platelet (PLT), clinical manifestations, and GVHD score of target organs (liver, lung, small intestine) in each group after transplantation were observed, and the differences of chimerism rate and survival rate in each group at 28 days after transplantation were compared. The interaction between Treg cells and NK cells in different proportions (1:1, 1:2, 1:6, 1:12) was investigated in vitro in mouse erythroleukemia (MEL) cells of mouse erythroleukemia. The results showed that at the 28th day of transplantation, the clinical manifestations and GVHD scores of target organs of mice in NK+ Treg (1:1) group and NK+ Treg (6:1) group were significantly lower than other groups (P < 0.05); the WBC and PLT counts were significantly higher than other groups (P < 0.05), and the survival time was significantly longer than other groups (P < 0.05); the clinical manifestations and GVHD scores of each target organ in NK+ Treg (1:1) group were significantly lower than those in NK+ Treg (6:1) group (P < 0.05); the chimerism rate of each group was >90% on day 28 after transplantation. In vitro experiments showed that the inhibition of Treg cells on NK cell killing activity was dose-dependent, and the proportion of 1:6 and 1:12, killing activity of NK cell was significantly lower than that of groups 1:1 and 1:2 (P < 0.05), which showed that allo-NK and allo-Treg alone had a significant effect on the improvement of GVHD after transplantation, and Treg cells inhibited the killing activity of NK cells by direct contact and showed a dose-dependent effect.

Efficacy of a chlorocresol-based disinfectant product on Toxocara canis eggs

Toxocara canis is a common parasite of dogs and can cause zoonotic toxocariasis in humans. As a part of control programs for this agent, optimized hygiene including chemical disinfection is considered essential in the prevention and control of zoonotic toxocariasis in humans. However, commonly used disinfectants at present mostly fail to inhibit the embryogenesis and viability of T. canis eggs. To this effect, the present study was designed to evaluate the effect of a chlorocresol-based disinfectant product Neopredisan®135-1 (NP) on embryonic development of T. canis eggs in vitro and to investigate the infectivity of exposed eggs by assessing larval establishment in a mouse model. Under in vitro conditions, NP at a final concentration of 0.25, 0.50, 1, 2, or 4% all exhibited significant killing effect on T. canis embryogenesis compared with the control eggs (P < 0.05), regardless of contact times (30, 60, 90, or 120 min). Such killing activity increased in a concentration- and time-dependent manner, with a maximum killing efficacy of 95.81% at 4% concentration and 120 min exposure time. Comparisons between low and high concentrations and between short and long contact times concluded that a protocol using the 1% concentration of NP with a 90-min contact could be the most suitable for practical application. Additionally, the lower larval recovery in mice inoculated with eggs treated by either 0.25 or 0.5% NP than that from their corresponding controls (P < 0.05) verified once again that NP had an adverse impact on the larval development of T. canis eggs even at a low concentration. To the best of our knowledge, this is the first study to report the effect of the chlorocresol-based disinfectant NP on the embryonation and larval development of T. canis eggs, and the results presented here would contribute to environmental clearance and control of toxocariasis by providing an alternative disinfectant resource. However, it is highlighted that the clearance of the novel and existing sources of infection including larvated eggs in places treated with NP is not guaranteed and therefore continuous monitoring and additional disinfection are still required.

Intelectin mediated phagocytosis and killing activity of macrophages in blunt snout bream (Megalobrama amblycephala)

Intelectin, a lectin discovered recently, has been identified in various vertebrate species, such as fish, amphibians, and mammals. In one of our previous studies, the efficient bacteria binding and agglutinating activity of the recombinant Megalobrama amblycephala intelectin protein (rMamINTL) and the enhanced immunopositive localization have been observed in the hepatic macrophage-like cells (kupffer cells) post Aeromonas hydrophila infection. Thus, the present study primarily focuses on the regulatory effects of rMamINTL on M. amblycephala macrophages. This study revealed a prominent LPS-binding activity of rMamINTL and a significantly increased phagocytosis of rMamINTL-treated A. hydrophila by M. amblycephala macrophages. However, the rMamINTL-treated M. amblycephala macrophages exhibited no evident regulatory effect on phagocytosis, whereas the enhanced killing activity of the rMamINTL-treated macrophages was observed, which may be attributed to the induced respiratory burst activity and the expression of inflammatory cytokines. In addition, the anti-proliferation effect of rMamINTL on two tumor cells was observed. However, its mechanism remains to be further studied. In short, these results show that MamINTL is a multifunctional immune protein with effective immunomodulatory activity.

Killing of Streptococcus pneumoniae by azithromycin, clarithromycin, erythromycin, telithromycin and gemifloxacin using drug minimum inhibitory concentrations and mutant prevention concentrations

Streptococcus pneumoniae continues to be a significant respiratory pathogen, and increasing antimicrobial resistance compromises the use of β-lactam and macrolide antibiotics. Bacterial eradication impacts clinical outcome, and bacterial loads at the site of infection may fluctuate. Killing of two macrolide- and quinolone-susceptible clinical S. pneumoniae isolates by azithromycin, clarithromycin, erythromycin, telithromycin and gemifloxacin against varying bacterial densities was determined using the measured minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC). For kill experiments, 10(6)-10(9) CFU/mL were exposed to the drug and were sampled at 0, 0.5, 1, 2, 3, 4, 6, 12 and 24 h following drug exposure. The log(10) reduction and percent reduction (kill) of viable cells was recorded. MICs and MPCs (mg/L) for azithromycin, clarithromycin, erythromycin, telithromycin and gemifloxacin were 0.063-0.125/0.5-1, 0.031-0.063/0.25-0.5, 0.063/0.25-0.5, 0.008/0.016 and 0.031/0.25, respectively. Killing 10(6)-10(9) CFU/mL of bacteria by the drug MIC yielded incomplete killing, however log10 reductions occurred by 12 h and 24 h for all drugs. Exposure of 10(6)-10(9) CFU/mL to MPC drug concentrations resulted in the following log(10) reduction by 6h of drug exposure: azithromycin, 1.3-3.9; clarithromycin, 1.9-5.8; erythromycin, 0.8-4.7; telithromycin, 0.3-1.7; and gemifloxacin, 1.8-4.2. Bacterial loads at the site of infection may range from 10(6) to 10(9), and kill experiments utilising a higher bacterial inoculum provided a more accurate measure of antibiotic performance in high biomass situations. Killing was slower with telithromycin. Kill was greater and fastest with MPC versus MIC drug concentrations.

Research on stress-induced apoptosis of natural killer cells and the alteration of their killing activity in mouse liver

AIM: To investigate the stress-induced apoptosis of natural killer (NK) cells and the changes in their killing activity in mouse livers.

METHODS: A restraint stress model was established in mice. Flow cytometry was employed to measure the percentage of NK cells and the changes in their absolute number in mouse liver. The cytotoxicity of hepatic and splenic NK cells was assessed against YAC-1 target cells via a 4 h 51Cr-release assay.

RESULTS: The restraint stress stimulation induced the apoptosis of NK cells in the liver and the spleen, which decreased the cell number. The number and percentage of NK cells in the spleen decreased. However, the number of NK cells in the liver decreased, whereas the percentage of NK cells was significantly increased. The apoptosis of NK cells increased gradually with prolonged stress time, and the macrophage-1 (Mac-1)⁺ NK cells were more susceptible to apoptosis than Mac-1^- NK cells. Large numbers of Mac-1^- NK cells in the liver, which are more resistant to stress-induced apoptosis, were observed than the Mac-1^- NK cells in the spleen. The stress stimulation diminished the killing activity of NK cells in the spleen was significantly decreased, but the retention of numerous Mac-1^- NK cells in the liver maintained the killing ability.

CONCLUSION: Significant stress-induced apoptosis was observed among Mac-1⁺ NK cells, but not Mac-1^- NK cells in the mouse liver. Stress stimulation markedly decreased the killing activity of NK cells in the spleen but remained unchanged in the liver.