Burn-associated Type Research Articles

Increased norepinephrine production associated with burn injuries results in CCL2 production and type 2 T cell generation

The susceptibility of thermally injured mice (TI-mice) to various infections is markedly influenced by burn-associated type 2 T cell responses, which are common with severe thermal injuries. Previously, we have reported that CC chemokine ligand 2/monocyte chemoattractant protein-I (CCL2) is produced in mice within 1 day of thermal injury, and the subsequent development of burn-associated type 2 T cell responses are triggered by this chemokine produced early after thermal injury. In this study, influence of norepinephrine (NE) on CCL2 production in mice early after thermal injury (TI) was investigated. Peripheral blood mononuclear cells (PBMC) and peritoneal macrophages (PMφ) from TI-mice produced CCL2, but the same cell preparations from normal mice did not. This chemokine was not produced by PBMC and PMφ from TI-mice previously treated with 6-hydroxydopamine (6-OHDA), which destroys sympathetic nerve termini. NE production was increased in circulation of TI-mice, and treatment of TI-mice with 6-OHDA resulted in the inhibition of NE secretion. When PBMC from normal mice were treated with NE, they acquired the ability to produce CCL2. Splenic T cells from TI-mice produced IL-4 into their culture fluids, while the cytokine was not produced by splenic T cells from TI-mice previously treated with 6-OHDA. These results indicate that NE may have an important role on early CCL2 production and the subsequent development of burn-associated type 2 T cell responses.

Soluble IL-4 receptor improves the skin-graft-associated cytomegalovirus infection in thermally injured mice

The susceptibility of thermally injured mice (TI-mice) to murine cytomegalovirus (MCMV) infection is markedly influenced by burn-associated type 2 T cell responses, which are common with severe thermal injuries. In the present study, the effect of soluble IL-4 receptor (sIL-4R) on the skin-graft-associated MCMV infection was investigated. The marked growth of MCMV was demonstrated in the salivary glands of TI-mice grafted with MCMV seropositive [MCMV sero(+)] skin. However, the growth of MCMV was not demonstrated in the salivary glands of TI-mice grafted with MCMV sero(+) skin and treated with 50 ng per mouse of sIL-4R. Compared with grafted normal mice, production of type 1 cytokines was markedly decreased when splenic T cells from TI-mice grafted with MCMV sero(+) skin were stimulated with anti-CD3 monoclonal antibody (mAb). The impaired type 1 cytokine production was recovered in cultures of splenic T cells from grafted TI-mice previously treated with sIL-4R. After grafting with MCMV sero(+) skin, the growth of MCMV was markedly inhibited in the salivary glands of severe combined immunodeficient (SCID) mice inoculated with T cells from TI-mice treated with sIL-4R. These results suggest that sIL-4R regulates the skin-graft-associated MCMV infection in TI-mice.

Therapeutic effects of IL-12 combined with benzoylmesaconine, a non-toxic aconitine-hydrolysate, against herpes simplex virus type 1 infection in mice following thermal injury

IL-12 is an inducer of type 1 T cell responses, which are essential in host defense against herpes simplex virus type 1 (HSV-1) infection. However, type 1 T cell responses are not elicited by IL-12 in thermally injured mice (TI-mice) that routinely have a predominance of burn-associated type 2 T cell responses. In our previous studies, benzoylmesaconine (BEN, an aconitine derivative extracted from heated- Aconiti tuber) induced the generation of CD4 + T cells antagonistic to type 2 T cells (BEN-CD4 + T cells). In the present study, the effects of a combination therapy using IL-12 and BEN to treat severe HSV-1 infection in TI-mice were investigated. When TI-mice were treated with either IL-12 (500 U per mouse) or BEN (1 μg/kg) alone, they did not resist HSV-1 infection. However, 60–80% of TI-mice exposed to HSV-1 survived after they received IL-12 and BEN or BEN-CD4 + T cells in combination. After stimulation with anti-CD3 mAb in vitro, IFN-γ was not produced in cultures of splenic T cells from TI-mice exposed to HSV-1 and treated with either IL-12, BEN or BEN-CD4 + T cell alone. However, IFN-γ production was induced by the mAb stimulation in the cultures of T cells from infected mice treated with IL-12 and BEN or BEN-CD4 + T cells in combination. These results suggest that the combination therapy of IL-12 (an inducer of type 1 T cell responses) and BEN (an inhibitor of type 2 T cell responses) may protect TI-mice from severe HSV-1 infection.

Effect of a combination therapy between IL-12 and soluble IL-4 receptor (sIL-4R) on Candida albicans and herpes simplex virus type I infections in thermally injured mice.

The effectiveness of a combination using IL-12 and soluble IL-4 receptor (sIL-4R) to treat severe infections of herpes simplex virus type 1 (HSV-1) and Candida albicans in thermally injured mice was investigated. Although sIL-4R decreased burn-associated type 2 T-cell responses, the effect of sIL-4R was minimal on the morbidity and mortality of thermally injured mice exposed to 250 times LD50 of HSV-1 or 10 times LD50 of C. albicans. Compared with 100% mortality in control mice, mortality for HSV-1 and C. albicans was 40 and 20%, respectively, in thermally injured mice that received IL-12 and sIL-4R in combination. After stimulation with anti-CD3 monoclonal antibody, splenic T cells from thermally injured mice exposed to large amounts of HSV-1 or C. albicans did not produce gamma interferon (IFN-gamma) into their culture fluids. However, IFN-gamma was produced by splenic T cells from thermally injured and infected mice treated with IL-12 and sIL-4R in combination. These results suggest that therapeutic treatment with a combination of IL-12 and sIL-4R may be effective by inducing type 1 T-cell responses in thermally injured mice exposed to large amounts of HSV-1 or C. albicans.

Cryptococcal encephalitis in thermally injured mice is accelerated by type 2 T-cell responses.

To explore the pathogenic role of burn-associated type 2 T-cell responses on the development of cryptococcal encephalitis in mice with severe thermal injuries. Experimental Cryptococcus neoformans infection in normal mice was compared with that in thermally injured mice (TI mice), normal mice treated with a mixture of interleukin (IL)-4 and IL-10, or normal mice inoculated with burn-associated type 2 T cells. University research laboratory. Male BALB/c mice, 8 to 10 wks of age. We prepared four groups of mice as follows: a) normal mice, b) TI mice, c) normal mice treated with the IL-4/IL-10 mixture, and d) normal mice inoculated with burn-associated type 2 T cells. These groups of mice were anesthetized and exposed to 1 x 10 cells/mouse of C. neoformans intratracheally. Cryptococcal growth in brains and lungs in normal mice were compared with those of the other three groups. Also, cytokine-producing profiles of T lymphocytes from brains of both normal mice and TI mice were determined. Compared with normal mice, TI mice were susceptible to C. neoformans infection. At the maximum (15 days after infection), numbers of C. neoformans organisms in brains of TI mice were 10 times higher than those of the pathogen in brains of normal mice. After stimulation with anti-CD3 monoclonal antibody, IL-4 (but not interferon gamma) was produced in cultures of T lymphocytes from brains of TI mice 15 days after the infection, whereas the same cell preparation from normal mice produced interferon gamma (but not IL-4). TI mice and mice that were treated with a IL-4/IL-10 mixture or inoculated with burn-associated type 2 T cells were equally susceptible to the cryptococcal infection. Burn-associated type 2 T cells or their cytokine products play a key role in the severity of cryptococcal encephalitis that develops in TI mice.

Appearance of monocyte chemoattractant protein 1 (MCP-1) early after thermal injury: role in the subsequent development of burn-associated type 2 T-cell responses.

To determine whether monocyte chemoattractant protein-1 (MCP-1), which initiates subsequent development of burn-associated type 2 T cells, is produced in mice early after thermal injury. A predominance of type 2 T-cell responses is commonly observed in animals and patients with severe thermal injuries. Burn-associated type 2 T cells have been identified as the cells responsible for the increased susceptibility of thermally injured mice to infections with herpes simplex virus type 1 and Candida albicans. Recently, the necessity of MCP-1 for the generation of type 2 T cells was shown in MCP-1 knockout mice. MCP-1 may have an important role in the increased susceptibility of thermally injured mice to various intracellular opportunistic pathogens. The production of MCP-1 in sera or in cultures of various cells prepared from thermally injured mice was measured. Dual-chamber transwell cultures were performed to determine the influence of MCP-1-producing cells on the generation of burn-associated type 2 T cells. Without any stimulation, splenic macrophages from mice (1/2D-M(phi)) produced MCP-1 into their culture fluids 12 hours after thermal injury. Interleukin-4 was detected in culture fluids of splenic T cells from normal mice cultured with 1/2D-M(phi) in a dual-chamber transwell system; however, this cytokine was not produced by normal T cells cultured with normal macrophages in the transwells. Also, normal T cells cultured with 1/2D-M(phi) did not produce interleukin-4 when transwell cultures were performed in the presence of anti-MCP-1 monoclonal antibody. Further, normal T cells directly stimulated with MCP-1 produced interleukin-4 into their culture fluids. Normal T cells, cultured with 1/2D-M(phi) for 24 hours in the transwells and recultured with fresh medium for an additional 7 days, produced interleukin-10 (but not interferon-gamma) and expressed ST2L mRNA (but not interleukin-12 receptor beta2 chain) when they were stimulated with anti-CD3 monoclonal antibody. Results indicate that MCP-1 is produced in mice within 1 day of thermal injury, and the subsequent development of burn-associated type 2 T-cell responses may be triggered by MCP-1 produced early after thermal injury.

Effects of glycyrrhizin, an active component of licorice roots, on Candida albicans infection in thermally injured mice.

Due to the generation of burn-associated CD8+ CD11b+ TCR gamma/delta+ type 2 T cells (burn-associated type 2 T cells), the susceptibility of thermally injured mice to infection with C. albicans has been shown to be increased by up to 50-fold when compared with normal mice. Glycyrrhizin (GR), an active component of licorice roots, reduced the susceptibility of thermally injured mice to C. albicans infection to levels observed in normal mice. Thermally injured mice inoculated with CD4+ T cells from GR-treated mice were also resistant to C. albicans infection. The following demonstrated that susceptibility to fungal infection was similar in thermally injured mice and normal mice inoculated with T6S cells (a clone of burn-associated type 2 T cells). This susceptibility of T6S mice (normal mice inoculated with T6S cells) was reversible by (i) administration of GR, (ii) inoculation of CD4+ T cells from GR-treated mice, and (iii) injection of a mixture of MoAbs targeted against type 2 cytokines (IL-4 and IL-10). After stimulation with anti-CD3 MoAb, splenic T cells from thermally injured and T6S mice, treated with GR or inoculated with CD4+ T cells from GR-treated mice, did not have type 2 cytokines in culture supernatants. They were present in splenic T cell cultures from thermally injured and T6S mice that were treated with saline or inoculated with naive T cells. These results suggest that GR, by inducing CD4+ T cells which suppress type 2 cytokines produced by burn-associated type 2 T cells, improves the resistance of thermally injured mice to C. albicans. An anti-type 2 T cell action of the CD4+ T cells derived from GR-treated mice was previously described.

Susceptibility of thermally injured mice to cytomegalovirus infection

Thermally injured patients are very susceptible to infection with cytomegaloviruses. In this study a role of burn-associated type 2 T cell responses on the cytomegalovirus infection was examined in a mouse model of thermal injury. A predominance of type 2 T cell responses in splenic lymphocytes of thermally injured mice has been previously demonstrated. SCID mice inoculated with splenic T cells from thermally injured mice were susceptible to infection with a small amount (5 PFU/mouse) of murine cytomegalovirus (MCMV). Conversely, SCID mice inoculated with splenic T cells from normal mice were resistant to the same infection. High levels of IL-4 and IL-10, but not IFN-γ and IL-2, were detected in sera of thermally injured mice (TI-mice) infected with MCMV when those were compared with sera of normal mice infected with MCMV. IL-4 and IL-10 (type 2 cytokines) were produced by splenic T cells from MCMV-infected TI-mice, when they were stimulated in vitro with anti-CD3 mAb. Type 1 cytokines (IFN-γ and IL-2), however, were not produced by these T cells after the same stimulation. In contrast, splenic T cells from MCMV-infected normal mice produced type 1 cytokines by the stimulation with anti-CD3 mAb. These results suggest that the susceptibility of mice to MCMV infection is markedly influenced by burn-associated type 2 T cell responses.

A Mechanism of Interleukin-12 Unresponsiveness Associated with Thermal Injury

An unresponsive state for the production of interleukin-12 (IL-12) is commonly observed in animals and patients with severe thermal injuries. In the present study, the participation of corticosteroids, prostaglandin E2 (PGE2), and type 2 cytokines, which appeared in association with thermal injury, on the burn-associated IL-12 unresponsiveness was studied. These substances have been described as inhibitors of IL-12 production. Less than 20 pg/ml serum IL-12 was produced in thermally injured mice (TI-mice) after stimulation with lipopolysaccharide (LPS), while 1037 pg/ml IL-12 was detected in sera of unburned mice equally stimulated with LPS. Almost complete restoration of the impaired IL-12 production was witnessed in TI-mice after treatment with soluble IL-4 receptor (50 ng/mouse, 2 h and 2 days after thermal injury). However, IL-12 was not induced by LPS stimulation in TI-mice treated with an inhibitor of PGE2 (indomethacin, 0.1–5 mg/kg) or an inhibitor of corticosteroid production (ketoconazole, 10 mg/kg). LPS-stimulated IL-12 production was also impaired in normal mice inoculated with burn-associated type 2 T cells. In addition, in the presence of 1 μg/ml LPS, naive macrophages cocultured with burn-associated type 2 T cells did not produce IL-12 in their culture fluids, while IL-12 was produced by LPS-stimulated naive macrophages that were cocultured with naive splenic CD8+ T cells. These results suggest that the IL-12-unresponsive state demonstrated in TI-mice is associated mainly with type 2 cytokines released from burn-associated type 2 T cells.

GLYCYRRHIZIN RESTORES THE IMPAIRED IL-12 PRODUCTION IN THERMALLY INJURED MICE

Mice 6 days after thermal injury (TI-mice) did not respond to lipopolysaccharide (LPS) stimulation for production of serum interleukin 12 (IL-12; 2h after LPS stimulation, <20pg/ml in TI-mice; 1091±162pg/ml in normal mice). However, 2h after LPS stimulation, 1456±118pg/ml of IL-12 were demonstrated in sera of TI-mice previously treated with a 10mg/kg i.p. dose of glycyrrhizin (GR). IL-12 was not induced by LPS in sera of normal mice inoculated with burn-associated type 2 T cells (IL-4/IL-10-producing CD8+CD11b+TCRγ/δ+T cells isolated from spleens of TI-mice). However, IL-12 production was induced by LPS in sera of these mice previously treated with GR or a mixture of monoclonal antibodies (mAbs) for type 2 cytokines. Also, IL-12 production was induced by LPS in TI-mice inoculated with CD4+T cells from spleens of GR-treated normal mice (GR-CD4+T cells, 5×106cells/mouse). Since GR-CD4+T cells have been shown to be antagonistic cells against production of type 2 cytokines by burn-associated type 2 T cells, these results indicate that IL-12 unresponsiveness shown in TI-mice is recovered by GR through the regulation of burn-associated type 2 T cell responses.

Therapeutic Protective Effects of IL-12 Combined with Soluble IL-4 Receptor Against Established Infections of Herpes Simplex Virus Type 1 in Thermally Injured Mice

The effect of combination therapy between IL-12 and soluble IL-4R (sIL-4R) on the established infection of HSV-1 in thermally injured mice (TI mice) was investigated. All of the TI mice infected with lethal amounts of HSV-1 died when IL-12 was given therapeutically at a dose of 500 U/mouse. However, 80% of these mice treated prophylactically with IL-12 survived compared with 0% survival of the same mice treated with saline. The therapeutic administration of IL-12 to TI mice currently infected with HSV-1 caused an 80% survival of these mice when the treatment was combined with sIL-4R. Although IL-12 did not stimulate IFN-gamma production in cultures of splenic T cells from TI mice, IFN-gamma was produced by stimulation with IL-12 when the producer cells were prepared from TI mice that had been treated previously with sIL-4R. After stimulation with anti-CD3 mAb, splenic T cells from TI mice with the established infection of HSV-1 produced IL-4 into their culture fluids. However, IL-4 was not produced by splenic T cells that were prepared from the same infected mice treated with IL-12 and sIL-4R in combination. The results obtained herein indicate that the efficacies of the combination therapy against the established infection of HSV-1 may result from the IFN-gamma production stimulated by IL-12 in TI mice that are treated with sIL-4R for reducing burn-associated type 2 T cell responses.

Biological properties of T6S cells, a clone of burn-associated type 2 T cells

A clone of type 2 T cells (T 6 S cell) was established from burn-associated CD 8+ CD 11 b+ TCR gamma/delta + type 2 T cells, and their biological properties were examined. After stimulation by anti-CD 3 monoclonal antibody (mAb), T 6 S cells produced IL-4 and IL-10 into their culture fluids. However, IFN-gamma and IL-2 were not demonstrated in the culture fluids of T 6 S cells stimulated with the mAb. The susceptibility of thermally injured mice to infection with herpes simplex virus type 1 (HSV-1) or Candida albicans (C. albicans) has been shown to be approximately 50 (C. albicans) to 100 (HSV-1) times greater than that of normal mice. As compared with the resistance of thermally injured mice to these pathogens, mice inoculated with 1 x 10(6) cells/mouse of T 6 S cells (designated as T 6 S-mice) showed the same susceptibility to the infections. When T 6 S-mice treated with a mixture of monoclonal antibodies (mAbs) directed against IL-4 and IL-10 were infected with a lethal dose of HSV-1 or C. albicans, their resistance to these pathogens was restored to levels found in normal mice. From the experiments using T 6 S-mice, it is suggest that type 2 T cells or their cytokine products (IL-4 and IL-10) may play an important role on the impaired resistance of thermally injured mice to certain opportunistic pathogens. T 6 S cell may be a useful tool to study opportunistic infections in hosts bearing type 2 T cells.

Burn-associated Candida albicans infection caused by CD30+ type 2 T cells.

Burn injury is associated with the greatly increased susceptibility of thermally injured patients to infection from a variety of pathogens. In this study we investigated the role of burn-associated type 2 T cells on the increased susceptibility of burned patients to Candida albicans infection using SCID mice and peripheral blood lymphocytes (PBL) from thermally injured patients. When SCID mice that were inoculated with PBL from healthy donors were resistant to C. albicans infection, the SCID mice that were inoculated with PBL from burned patients did not show any resistance to the infection. All SCID mice exposed to the pathogen, however, survived after inoculation with patient PBL that were previously depleted of CD30+ cells. The predominance of type 2 T cell responses was demonstrated in PBLs of thermally injured patients. As burn-associated type 2 T cells, CD3+ CD8+ CD30+ IL-4 and IL-10-producing cells were demonstrated in burned patient PBL. These results suggest that burn-associated CD30+ type 2 T cells may play a role on the increased susceptibility of burned patients to C. albicans infection.

A relationship between the generation of burn-associated type 2 T cells and their antagonistic cells in thermally injured mice

Anti-type 2 T cells, generated in the spleens of thermally injured mice following the appearance of burn-associated CD8 +, CD11b +, TCRγ δ + type 2 T cells (BA2T cells), have previously been shown to improve the resistance of thermally injured mice to Herpes virus infections. Anti-type 2 T cells, CD4 +, CD28 +, TCRα β + , IFN-γ-producing T cell, are able to counteract the activity of BA2T cells which have been shown to be key cells in the increased susceptibility of thermally injured mice to these infections. In the present study, part of the generation mechanisms of anti-type 2 T cells was examined in mice. Anti-type 2 T cells were detected in the spleens of unburned mice 3–7 days after i.v. inoculation (2 × 10 6 cells/mouse) of BA2T cells or a BA2T cell clone, defined as T6S cells. The suppressor cell activity of T6S cells was completely inhibited when they were co-cultured with anti-type 2 T cells from mice inoculated with T6S cells. Similar phenotypic and biological profiles of anti-type 2 T cells acquired from burned mice were expressed by T6S cell-induced anti-type 2 T cells. These results indicated that anti-type 2 cells may be generated in response to the appearance of BA2T cells in thermally injured mice. Immunoregulatory circuits may be involved in the generation of anti-type 2 T cells.