Noritada Kobayashi

Effect of hot water extract of Chlorella vulgaris on cytokine expression patterns in mice with murine acquired immunodeficiency syndrome after infection with Listeria monocytogenes

We have previously reported that oral administration of hot water extract of Chlorella vulgaris (CVE) enhances resistance to Listeria monocytogenes through augmentation of Listeria-specific cell-mediated immunity in normal mice and mice with murine acquired immunodeficiency syndrome (MAIDS) caused by murine leukemia virus (MuLV) LP-BM5. To elucidate the mechanisms whereby CVE augments the cell-mediated immunity, we examined the expression patterns of mRNA for cytokines in normal and MAIDS mice given CVE orally after L. monocytogenes infection. The expression levels of IL-1 alpha, IL-12, GM-CSF, MIP and TNF alpha genes were significantly augmented in the peritoneal adherent cells by oral administration of CVE for 2 weeks before Listeria infection. The expression levels of gamma IFN and IL-12 mRNA were significantly higher in the spleen after Listeria infection in CVE-treated mice than in normal mice, while the expression of IL-10 mRNA in the spleen was decreased by CVE administration. In MAIDS mice, oral administration of CVE also augmented the expression of gamma IFN and IL-12 mRNA in the spleen after Listeria infection, while it rather reduced the expression of IL-10 mRNA. These results suggest that CVE may preferentially augment THI responses against Listeria via activation of macrophages to produce IL-12 and enhance host defence against Listeria infection both in normal and MAIDS mice.

A sustained increase of cytosolic Ca2+ in γδ T cells triggered by co-stimulation via TCR/CD3 and LFA-1

Abstract We previously reported that co-stimulation with LFA-1 triggered apoptosis in γδ T cells but not in αβ T cells after TCR engagement. We extended our earlier study on TCR/LFA-1 triggered apoptosis to two autoreactive TCR γδ and TCR αβ T cell clones, which were derived from syngeneic mixed lymphocyte culture of BALB/c mice. A γδ T cell clone, KM1, expressed the Vγ4 and Vδ5 genes and CD4-CD8-CD45RB+ phenotype; and an αβ T cell clone, BASL1.1, expressed Vβ6 and CD4+CD8-CD45RB+. Both clones produced Th-1-type cytokines in response to syngeneic BALB/c stimulator cells. KM1 underwent apoptosis upon stimulation with immobilized anti-CD3/LFA-1 mAbs, whereas BASL1.1 could proliferate successfully in response to stimulation with the immobilized mAbs. BASL1.1 was able to down-regulate the increased cytosolic Ca2+ after the simultaneous stimulation, but KM1 exhibited a sustained increase of cytosolic Ca2+ after stimulation via CD3 and LFA-1. Similar results with respect to the kinetics of cytosolic Ca2+ were obtained with normal heterogeneous γδ and αβ T cell populations after co-stimulation via CD3 and LFA-1. Our results suggested that persistently high levels of cytosolic Ca2+ might be related to apoptosis in γδ T cell clone triggered by costimulation via CD3 and LFA-1.

Th0-like CD4+ T cells protect mice with murine retrovirus-induced immunodeficiency syndrome (MAIDS) against co-infection with Listeria monocytogenes.

We examined the host defence mechanism against infection with Listeria monocytogenes, a facultative intracellular bacterium, in mice with murine acquired immunodeficiency syndrome (MAIDS) caused by LP‐BM5 murine leukaemia virus (MuLv) infection. Although LP‐BM5 MuLV infection in C57BL/6 mice leads to a stage of immunodeficiency characterized by severe compromise of cell‐mediated immunity, the mice with established MAIDS infected with LP‐BM5 8 weeks previously, showed resistance to an intraperitoneal infection with Listeria monocytogenes. These MAIDS mice also showed resistance to a lethal dose of secondary listerial challenge, while the delayed‐type hypersensitivity response to heat‐killed Listeria (HKL) was severely impaired in MAIDS mice. The resistance of MAIDS mice to listerial infection was mediated by CD4+αβ T cells but neither by γδ T cells nor natural killer (NK) cells. Interferon‐γ (IFN‐γ) and interleukin‐10 (IL‐10) were produced by CD4+ T cells from Listeria‐infected MAIDS mice in response to the in vitro stimulation with HKL, whereas IFN‐γ but not IL‐10 were produced by those from Listeria‐infected control mice. These results suggest that T‐helper 0 (Th0)‐like immune responses of CD4+ T cells occur and participate in host defence mechanisms against listerial infection in MAIDS mice.