The effect of thymulin on avian IL-2 receptor expression

Therapeutic Agents Rounding Up the Immunopathology of COVID-19

COVID-19 pandemic has caused more than 3 million deaths globally during the past year. The direct attack from SARS-CoV-2 and hyperactivated immune response contribute to the progress and deterioration of COVID-19. After the virus invades, the activation and release of cytokines/chemokines cause "cytokine storm", leading to acute respiratory distress syndrome (ARDS) and multiple organs dysfunction syndrome (MODS). Eliminating virus and blocking cytokines are important checkpoints of COVID-19 therapy, and several agents targeting immunopathology, including interferons, thymosin, glucocorticoids and immunoglobulin, have shown therapeutic effects in severe patients with COVID-19. Herein, we reviewed the practice evidences and concluded that several agents rounding up the immunopathology of COVID-19 may be the alternative approaches under the scenario of the lacking of effective antiviral drugs.

Development of broiler chickens after treatment with thymulin 5cH: a zoo technical approach

Modulation of immune response due to thymulin 5cH has been previously observed. The aim of the present study is to evaluate the development of broiler chickens treated with thymulin 5cH by conventional zoo technical indices, phytohemaglutinin induced inflammation test and histomorphometric analysis of lymphoid organs (thymus, Fabricius bursa and spleen). Animals were divided in two groups: (a) test: birds with free access to thymulin 5cH diluted into the drink water and (b) control: birds with free access to water only, from the 1st to the 42nd day of life. All experimental procedures were done in blind. The results show that thymulin 5cH treated group had increased productivity index compared to control (391.45 versus 261.93) associated with higher viability in the 7th week (p = 0.013), and a possible shunt to B lymphocyte activity. The data suggest that thymulin 5cH could be a viable method to improve productivity in poultry production due to its immune modulation properties.

Thymulin, a thymic peptide, prevents the overproduction of pro-inflammatory cytokines and heat shock protein Hsp70 in inflammation-bearing mice

The effects of synthetic analogue of peptide hormone thymulin, which is normally produced by thymic epithelial cells, on immune cells activity and blood cytokine profile had been studied in male NMRI mice with acute inflammation induced by injection of lipopolysaccharide from gram-negative bacteria (LPS, 250 microg/100 g of body weight). Inflammation induced by LPS resulted in accumulation of several plasma pro-inflammatory cytokines, IL-1 beta, IL-2, IL-6, TNF-alpha, interferon-gamma, and also IL-10, anti-inflammatory cytokine. Thymulin previously injected in dose of 15 microg/100 g body weight, prevented the accumulation of proinflammatory cytokines in plasma. Thymulin also prevented LPS-induced up-regulation of production of several cytokines by spleen lymphocytes and peritoneal macrophages. Added in vitro, thymulin decreased the peak of TNF-alpha production in macrophages cultivated with LPS. In addition, thymulin lowered the peak of Hsp70 production induced by LPS treatment. The results indicate that thymulin having significant anti-inflammatory effect may be promising in clinical application.

Zinc-binding proteins (metallothionein and alpha-2 macroglobulin) and immunosenescence

Zinc is a relevant trace element for the efficiency of the entire immune system. The binding of zinc with some proteins, such as metallothioneins (MT) and alpha-2 macroglobulin (alpha-2M) is crucial for the immune efficiency during ageing and in age-related diseases, because these proteins may be involved in antagonistic pleiotropic effects. Indeed, the presence of chronic inflammation during ageing, generally, induces overexpression of these proteins that, due to their original biological function in fighting stressor agents, continuously sequester intracellular zinc. As a consequence, a low zinc ion availability may appear in aged organisms leading to impairments of the immune response at thymic and extrathymic levels with the risk of the appearance of age-related diseases. Therefore, MT and alpha-2M turn from protective in "young-adult age" to harmful agents in "ageing" following the basic assumption of an evolutionary theory of ageing, named the "antagonistic pleiotropy", which suggests that a trade off between early beneficial effects and late negative outcomes can occur at a genetic and molecular level. On the other hand, some polymorphisms of MT (MT2A) and alpha-2M have been associated with atherosclerosis or Alzheimer disease, respectively. Physiological zinc supplementation in elderly restores the thymic endocrine activity and innate immune response (NK cell cytotoxicity) and increases the survival rate in old mice. Therefore, zinc supplementation is useful to achieve health longevity because these zinc-binding proteins may regain their original protective task against oxidative damage with, thus, a beneficial impact on immune response.

Developmental immunotoxicity of lead: Impact on thymic function

BACKGROUND

Since the potential effects of early exposure to lead on thymic functions have not been fully characterized, in this study we evaluated the capacity of lead to alter thymic function in juvenile chickens following embryonic exposure.

METHODS

Cornell K strain White Leghorn chicken eggs were administered lead acetate (400 microg/egg) or sodium acetate (control) on embryonic development (E12) with and without thymulin supplementation. Ex vivo production of interferon-gamma (IFN-gamma)-like cytokine by thymocytes and a delayed-type hypersensitivity (DTH) reaction were measured in the juvenile. Additionally, the effects of in vitro exposure to lead on both thymocytes and thymic stromal cells (TSCs) were evaluated.

RESULTS

Following E12 exposure to lead, ex vivo production of IFN-gamma-like cytokine by juvenile-derived thymocytes decreased significantly compared to the control. The same effect was observed when thymocytes were directly exposed to lead in vitro and stimulated with thymic stromal supernatant. In contrast, when TSCs were exposed to lead in vitro, no change was seen in their functional capacity for promoting cytokine production. In ovo supplementation with thymulin partially reversed lead-induced DTH depression without any change in IFN-gamma-like cytokine production. Embryonic exposure to thymulin alone partially depressed the DTH response.

CONCLUSIONS

These results suggest that lead can directly influence thymocyte function in the absence of the thymic microenvironment. Since thymulin levels may influence lead-induced immunotoxicity, embryonic endocrine status may be an important consideration. Lead exposure appears to alter thymic functions directly; however, indirect effects via endocrine factors are not precluded.

In vivo thymulin treatments enhance avian lung natural killer cell cytotoxicity in response to infectious bronchitis virus

Previous work has shown that in vitro thymulin treatments have the ability to enhance natural killer (NK) cell cytotoxicity. The purpose of the experiments presented here was to examine the in vivo effects of thymulin on avian NK cell activity in response to a viral infection. Five and a half-week-old K-strain chickens infected with avian infectious bronchitis virus (IBV) served as the model for these experiments. Daily thymulin injections began at varying time points prior to or post-infection. The controls received daily injections of the ZnCl(2)-containing carboxymethyl-cellulose (CMC) diluent. A 51Cr-cytolytic release assay was used to determine the activity of the NK cells harvested via lung lavage from the respiratory tracts of infected chickens. The results of these experiments showed that in vivo thymulin treatments enhance NK cytotoxicity. The greatest enhancement of NK cytotoxicity was observed at 10 days post-infection in those chickens that began receiving thymulin after infection. These results suggest that thymulin may not only have a role in enhancing immunosurveillance but also in enhancing the response of the innate immune system following infection. Dose-response experiments found that the 50 ng/100 g body weight (Bwt) dose significantly depressed the cytolytic activity of the NK cells in comparison to either the 10 ng/100 g Bwt dose or the control.

The enhancement of avian NK cell cytotoxicity by thymulin is not mediated by the regulation of IFN-gamma production

Preincubation with either thymulin or IFN-gamma can enhance NK activity. In addition, overnight in vitro pre-treatment with thymulin and IFN-gamma increases NK activity further than either treatment alone. It has been hypothesized that thymulin increases the responsiveness of immune cells to IFN-gamma by either increasing the expression of IFN-gammaR or by increasing the production and/or secretion of IFN-gamma. The effects of thymulin on IFN-gamma production and secretion were examined in this study. While an overnight incubation with the polyclonal activator Con A increased the number of cells positive for intracellular IFN-gamma, a similar incubation with thymulin produced no change in the percentages of cells labeling positive for intracellular IFN-gamma when compared to the media control cells. In addition, IFN-gamma was not secreted by splenocytes following an overnight incubation with thymulin, but increased secretion was induced by Con A stimulation. Taken together, these results suggest that thymulin does not increase IFN-gamma production or induce IFN-gamma secretion by avian splenocytes.

The effects of thymulin on macrophage responsiveness to interferon-gamma

The effect of in vivo and in vitro thymulin treatments on macrophage responsiveness to interferon-gamma was evaluated in chickens. Seven-week-old chickens were treated with 0, 1, 10, or 100ng thymulin per 100g body weight. Abdominal exudate cells (AEC), a source of macrophages, were harvested and cultured in the presence of graded levels of recombinant chicken interferon-gamma (ChIFN-gamma). Responsiveness to ChIFN-gamma was determined by measuring the induction of nitric oxide production. One and 2-day thymulin treatment at 10 and 100ng per 100g body weight doses significantly increased responsiveness to ChIFN-gamma while 1ng per 100g body weight had no effect. Other experiments compared the effect of thymulin treatments in Cornell K strain chickens, having normal serum thymulin levels with sex-linked dwarf (SLD) chickens which are deficient in serum thymulin. The dose of thymulin treatment required to significantly increase responsiveness to ChIFN-gamma differed between strains. Finally, the effect of direct in vitro thymulin treatments on macrophage responsiveness to ChIFN-gamma was evaluated. There were no significant increases in responsiveness to ChIFN-gamma between treatment groups within the macrophage cell line, HD-11, when cultured in the presence of 0-200pg thymulin/ml. These data suggest that the effect of thymulin on AEC responsiveness to ChIFN-gamma is indirectly mediated.

The effects of triodothyronine and thymulin on avian NK cytolytic activity

The effects of triiodothyronine (T3), thymulin, and recombinant chicken interferon-y (ChIFN-gamma) on natural killer (NK) cell cytotoxicity was investigated using the euthyroid control K and the T3-deficient sex-linked dwarf (SLD) chicken strains. Factorial design experiments were used to investigate the effects of T3 treatments where animals of both strains received either 0 or 0.1 ppm T3 supplementation to the standard chick starter diet. The ChIFN-gamma treatments were administered in vitro by incubation with effector cells overnight prior to the addition of the RP9 lymphoblastoma target cell line. All cytotoxicity assays were run at 50:1 and 25:1 effector/target (E/T) ratios. Treatments were begun at hatching and continued through 7 weeks. NK cells for these assays were enriched by separation of splenocytes over ficoll. Splenocyte preparations from untreated K strain consistently had significantly higher NK-mediated cytolysis than did samples from the untreated SLD at both E/T ratios. T3 treatment alone had no effect on NK activity in cell preparations from the K strain but did significantly enhance that activity in the T3-deficient SLD whereas IFN treatment alone enhanced NK activity in both strains. The combined T3 and IFN treatments resulted in a greater enhancement of NK cytolytic activity in both strains than any separate treatment and resulted in an elimination of differences in NK cell responsiveness between the K and SLD strains. Similar results were obtained when NK cell cultures were incubated in vitro with thymulin prior to assessing cytotoxicity. In vitro thymulin treatments alone significantly enhanced cytolytic activity for NK cells for both K and SLD strains. The greatest effect of in vitro thymulin exposure was to increase the responsiveness to NK cells to ChIFN-gamma stimulation.

Evidence for the direct action of thymulin on avian NK cells

The ability of thymulin to directly enhance NK cell-mediated cytotoxicity was examined. Specific cell population depletions were done in K and SLD chicken splenocyte preparations using anti-CD3, CD4, and CD8 monoclonal antibodies and secondary complement-fixing polyclonal antibodies. The remaining cells were incubated overnight with in vitro treatments of thymulin and IFN-gamma, either separately or together, followed by an assay for cytotoxicity. Although the control K-strain had higher overall NK cell-mediated cytotoxicity than the thymulin-deficient SLD-strain, the following trends were seen in both strains. Thymulin continued to enhance NK activity following CD4 or CD3 cell depletion, but not after CD8 or CD8 and CD4 cell depletion. Since avian NK cells express CD8 alpha, but not CD3 or CD4 on their surface, these results suggest that the ability of in vitro thymulin treatments to enhance NK activity is not mediated by T-cells but may be due to direct effects on NK cells.