Chikako Miyaji

Functional alteration of granulocytes, NK cells, and natural killer T cells in centenarians

The immune system in centenarians was characterized as elevated levels in the proportion and number of granulocytes, NK cells, and extrathymic T cells (including NKT cells) in the peripheral blood. Conventional T cells, abundant in youth, were decreased in proportion and number. In addition to this numerical change in centenarians, the function was significantly altered in comparison with that in middle-aged subjects. The phagocytic function and cytokine production of granulocytes in centenarians increased whereas the production of superoxides from granulocytes decreased. This tendency was almost the same in both healthy and unhealthy centenarians. IFN gamma production by NK and extrathymic T cells in centenarians seemed to be augmented and resulted in an elevated level of serum IFN gamma. Possibly due to the effect of this endogenous IFN gamma, the proportion of CD64(+) (Fc gamma RI) cells among granulocytes was elevated. The expansion of CD64 antigens on granulocytes is known to be regulated by IFN gamma and to be associated with their induction of phagocytosis. These results suggest that the immune system of centenarians is not merely impaired, but altered in terms of the number and functions of granulocytes, NK cells, NKT cells.

Immunopotentiation of intraepithelial lymphocytes in the intestine by oral administrations of β-glucan

Mice were orally administered with beta-glucan, isolated from bakers yeast, daily for one week (25mg/day/mouse) and several immunoparameters in the digestive tract were examined. The most prominent change was an increase in the number of intraepithelial lymphocytes (IEL) in the intestine, although the number of lymphocytes in the liver remained unchanged. The absolute number of both alphabetaT cells and gammadeltaT cells expressing CD8 antigens increased among IEL in the intestine. Primarily, liver lymphocytes showed a spontaneous production of Type 0 cytokine (simultaneous production of IFNgamma and IL-4) while IEL did not produce any cytokines without stimulation. However, mice administered with beta-glucan produced Type 1 cytokine, namely, production of IFNgamma alone. These results suggest that beta-glucan may be an important potentiator for mucosal immunity in the digestive tract.

Numerical and functional characteristics of lymphocyte subsets in centenarians

The immune system in the aged is a very interesting subject for study. In this study, analysis was extended to extrathymic T cells as well as NK cells and “conventional” T cells (i.e., thymus-derived T cells) in terms of their constitution and function in both healthy and unhealthy centenarians. Middle-aged persons were used as controls. Healthy and unhealthy centenarians showed lower levels in the proportion and absolute number of lymphocytes. The major change in the constitution of lymphocyte subsets was increased levels in the proportion of NK cells (CD56+/CD57+) and extrathymic T cells (CD3+CD57+). Inversely, conventional T cells decreased in proportion and function (i.e., proliferative response to mitogen). Although NK cells increased in centenarians, NK activity by whole lymphocytes and the purified NK fraction decreased. The difference between healthy and unhealthy centenarians was small in all parameters, the only difference being a lower level of expression of CD56 antigens on CD57+ T cells in unhealthy centenarians. These results indicate that there is a major shift in lymphcyte population from conventional T cells to NK cells and extrathymic T cells with aging. Concerning the age-associated increases in CD56+ T and CD57+ T cells, these cells correspond to NK1+ T cells in mice.

Role of macrophage scavenger receptor in endotoxin shock.

Lipopolysaccharide (LPS) is known to bind to several receptors on macrophages, including CD14 and macrophage scavenger receptor class A types I and II (MSR‐A), and stimulates macrophages to release various inflammatory mediators. MSR‐A recognizes a broad range of polyanionic ligands such as chemically modified lipoproteins, LPS of Gram‐negative bacteria, and lipoteichoic acid of Gram‐positive bacteria, suggesting a role in host defence. In this study, mice lacking MSR‐A were used to elucidate the role of MSR‐A in endotoxin shock. Peritoneal macrophages from MSR‐A‐deficient (MSR‐A−/−) mice bound less remarkably to LPS than those from wild‐type (MSR‐A+/+) mice and the binding activity of MSR‐A+/+ macrophages to LPS was reduced by the addition of an anti‐MSR‐A antibody. Clearance of LPS in serum was retarded in MSR‐A−/− mice after intraperitoneal administration of LPS. LPS‐induced expression of cytokines in the liver was similar in MSR‐A+/+ and MSR‐A−/− mice, but levels of interleukin (IL)‐1β expression and serum IL‐1β were lower in MSR‐A−/− mice. Administration of large doses of LPS resulted in a higher mortality of MSR‐A+/+ mice and pretreatment with an IL‐1 receptor antagonist reduced the mortality. Thus, MSR‐A‐mediated macrophage activation plays a negative role in protecting mice from endotoxin shock by enhancing IL‐1β production by macrophages. Copyright

Enforced Expression of Bcl-2 Restores the Number of NK Cells, But Does Not Rescue the Impaired Development of NKT Cells or Intraepithelial Lymphocytes, in IL-2/IL-15 Receptor β-Chain-Deficient Mice

IL-2/IL-15Rβ-deficient mice display impaired development of NK cells, NKT cells, and intraepithelial lymphocytes of the intestine and skin. To determine the role of survival signals mediated by IL-2/IL-15R in the development of these innate lymphocytes, we introduced a bcl-2 transgene into IL-2/IL-15Rβ-deficient mice. Enforced expression of Bcl-2 restored the number of NK cells in IL-2/IL-15Rβ-deficient mice, but the rescued NK cells showed no cytotoxic activity. The numbers of NKT cells and intestinal intraepithelial lymphocytes did not increase significantly, and skin intraepithelial lymphocytes remained undetectable in the bcl-2 transgenic IL-2/IL-15Rβ-deficient mice. These results indicate an essential role of IL-2/IL-15R-mediated survival signals in the development of NK cells, but they also show that additional nonsurvival signals from IL-2/IL-15R are necessary for innate lymphocyte development.

Expansion of unconventional T cells with natural killer markers in malaria patients

Immunological states during human malarial infection were examined. In parallel with parasitemia and anemia, granulocytosis was induced in the blood of patients, especially those infected with Plasmodium (P.) falciparum. At that time, the level of lymphocytes remained unchanged or slightly increased in the blood. However, the distribution of lymphocyte subsets was modulated, showing that the proportion of CD56(+)T cells, CD57(+)T cells, and gammadeltaT cells (i.e. all unconventional T cells) had increased in patients infected with P. falciparum or P. vivax. This phenomenon occurred at the early phase of infection and disappeared in the course of recovery. The data from patients with multiple attacks of P. vivax infection showed that there was no augmentation of these responses. In adult cases, the increase in the proportion of unconventional T cells seemed to closely parallel disease severity. However, all these responses were weak in children, even those infected with P. falciparum. In conjunction with accumulating evidence from mouse malaria experiments, the present results suggest that the immunological state induced by malarial infection might mainly be an event of unconventional T cells and that the immunological memory might not be long-lasting, possibly due to the properties of unconventional T cells.

Suppressive Effect of Antiulcer Agents on Granulocytes—A Role for Granulocytes in Gastric Ulcer Formation

Many clinicians have believed that H2-blockers and proton pump inhibitors ameliorate gastric ulcers via their antacid function. We examined the effects of these antacids on granulocytes. Gastric ulcer patients were administered an H2-blocker or proton pump inhibitor for a week and the number of granulocytes and the superoxide production were examined. To determine the trafficking of granulocytes, mice were exposed to restraint stress for 24 hr. The H2-blocker decreased the number of granulocytes, while the proton pump inhibitor suppressed their superoxide production in humans and mice. The major function of H2-blockers and proton pump inhibitors in curing gastric ulcers seems to be their suppressive effects on granulocytes. In this case, stress accelerates the trafficking of granulocytes from the bone marrow to the gastric mucosa. If we demonstrate a role for granulocytes in gastric ulcer formation, an gap in the acid–pepsin theory and the Helicobacter pylori theory is filled in.

Therapeutic effects of glycyrrhizin in mice infected with LP-BM5 murine retrovirus and mechanisms involved in the prevention of disease progression

Glycyrrhizin (GL), a plant extract, has been evaluated for its inhibitory effect on HIV replicationin vitro and for its improvement of clinical symptoms in HIV-infected patients. In this study, we used GL in a murine AIDS model (MAIDS) to evaluate these effects. C57BL/6 mice were inoculated with LP-BM5 murine leukemia virus to cause MAIDS. Treatment with GL supplemented with glycine and cysteine (Stronger Neo-Minophagen C, SNMC) was then begun on day 0 or 4 wks after virus inoculation. SNMC was administered three times a week for up to 19 wks. Immunological abnormalities were monitored with respect to the surface phenotype identified by two-color staining for CD3 and IL-2 receptorβ-chain. All mice infected with the virus alone developed MAIDS and died by 14 wks after infection. The immunopathogenesis was estimated to be an abnormal expansion of intermediate CD3 cells (i.e., extrathymic T cells) as well as other types of lymphocytes. SNMC did not change the total mortality rate. However, some mice that began the treatment on day 0 or 4 wks after infection survived 3 wks longer. Splenomegaly and lymphadenopathy in such mice were suppressed. These mice showed normal phenotypic features and normal responses to Con A. These results suggest that SNMC is effective in some MAIDS mice in preventing the progression of disease. When lymphocytes isolated from the liver, spleen and lymph nodes of diseased mice were culturedin vitro, they showed a spontaneous proliferation. Interestingly, such proliferation was inhibited by addition of liver lymphocytes, but not splenic lymphocytes, obtained from normal or SNMC-treated mice. Since liver lymphocytes contains intermediate CD3 cells with autoreactivity, they may possibly suppress the progression of disease.

Unconventional NK1.1– intermediate TCR cells as major T lymphocytes expanding in chronic graft‐versus‐host disease

Chronic graft‐versus‐host disease (GVHD) accompanying autoimmune disease was induced in (C57BL/6×DBA/2) F1 mice (H‐2b/d) by an injection of splenic T cells of parental DBA/2 origin (H‐2d). In parallel with the onset of proteinuria, an expansion of lymphocytes was induced in the liver and kidney, showing a peak at 2 weeks after the onset of disease. The majority of lymphocytes were of recipient origin (H‐2b/d). The main lymphocyte subset among T cells at the pre‐onset stage and after the onset of disease was CD8+ NK1.1– CD3int cells (of extrathymic, hepatic origin) in both the liver and kidney. NK1.1– CD3int cells confer primarily neither NK‐like nor NKT‐like cytotoxicity. No induction of these types of cytotoxicity was observed in these mice with the expansion of NK1.1– CD3int cells. This raised the possibility that granulocytes induced in the liver and kidney might be associated with tissue damage. The present results suggest that, similarly to the case of autoimmune‐prone mice with genetic background (e.g. MRL‐lpr/lpr mice and BXSB mice), NK1.1– CD3int cells of extrathymic, hepatic origin might be crucial lymphocytes involved in the induction of the autoimmune‐like disease in mice with chronic GVHD, in conjunction with Bcells (e.g. B‐1 cells).

Mechanisms underlying the activation of cytotoxic function mediated by hepatic lymphocytes following the administration of glycyrrhizin.

Stronger neo-minophagen C (SNMC), a glycyrrhizin (GL) preparation, has been used for the treatment of chronic viral hepatitis. It has been reported that a single administration of SNMC induced the activation of hepatic lymphocytes in number and function in animal studies. However, it is still unknown how SNMC augments the cytotoxic function and why such augmentation of cytotoxicity occurs in the liver and other organs. In this study, SNMC was daily injected into mice (2 mg GL/day/mouse) for 2 weeks. A significant augmentation of cytotoxicity mediated by NK cells, NKT cells and TNFalpha was demonstrated mainly in the liver. The presence of TNFalpha-mediated cytotoxicity in the liver was demonstrated for the first time. In contrast to CD8+ cytotoxic T cells (CD8+ CTL), all these cytotoxicities were preexistent in lymphocytes without the immunization of a specific antigen or alloantigens. NK cytotoxicity was mediated by a perforin system, while NKT cytotoxicity was mediated by a Fas ligand system. The present results suggest that the entire cytotoxic function mediated by hepatic lymphocytes was simultaneously augmented by SNMC.