A significant role of the macrophage accumulation induced by MCF in the protection of mice against Listeria monocytogenes in vivo

Restraint stress-induced elevation of endogenous glucocorticoid suppresses migration of granulocytes and macrophages to an inflammatory locus

It has been reported that restraint stress gives rise to various immunosuppressive events. In the present study, we focused our interest on an early stage of the host-defense system in which granulocytes, macrophages and natural killer (NK) cells are involved. We observed that an elevation of endogenous glucocorticoid levels in mice induced by 24 h-restraint stress (acute stress) did not significantly reduce the NK activity of the spleen cells but profoundly suppressed the migration of macrophages and granulocytes into peritoneal cavities of the mice at 24 h after an intraperitoneal injection of proteose peptone. The reduced number of the migrated granulocytes and macrophages corresponded to a down-regulated gene expression of such chemotactic factors as MCP-1/JE in the peritoneal exudate cells of the stress-loaded mice. The stress-loaded mice recovered from such a suppressive state upon treatment with the glucocorticoid antagonist, RU-486, or upon adrenalectomy, suggesting that the elevated level of endogenous glucocorticoid is responsible for these suppressive effects of acute stress.

Augmentation of host resistance to Listeria monocytogenes infection by a traditional Chinese medicine, ren-shen-yang-rong-tang (Japanese name: ninjin-youei-to)

Ren-shen-yang-rong-tang (Japanese name: Ninjin-youei-to, NIN), a traditional Chinese medicine, is a drug made of spray-dried powder of hot water extract obtained from twelve species of medical plants. An intraperitoneal (ip) injection with NIN 2 days before intravenous (iv) infection with Listeria monocytogenes (L. monocytogenes) accelerated elimination of viable bacteria in the spleen in the early stage of infection (from day 1) and protected mice from the lethal infection. It was suggested that the protective effect of NIN was mediated by the activation of nonimmune macrophages playing a principle role in resistance in the early stage of infection. Two days after ip injection with NIN just before infection, significantly increment in the number of monocytes in the peripheral blood was observed, though macrophage number in the spleen and their intracellular killing activity were unchanged. At 12 hours after infection with L. monocytogenes, a significantly enhanced increase of splenic macrophage number was observed in NIN-treated mice, compared to controls. After ip injection of NIN, interleukin-1 (IL-1), IL-6 and granulocyte macrophage-colony stimulating factor (GM-CSF) became detectable in the serum or peritoneal cavity. These results suggested that NIN stimulated macrophage-precursor cells in the bone marrow via the production of IL-1, IL-6, GM-CSF by macrophages, accelerated the supply of peripheral macrophages, and such macrophages accumulated into the site of infection in the very early stage of infection. Similar protective effects of NIN were observed by oral administration for 7 days till 1 day before iv infection with L. monocytogenes.

Effect of a traditional Chinese medicine, bu-zhong-yi-qi-tang (Japanese name: Hochu-ekki-to) on the protection against Listeria monocytogenes infection in mice

Effects of Bu-Zhong-Yi-Qi-Tang (Japanese name: Hochu-ekki-to) on the resistance against Listeria monocytogenes were observed in ICR mice orally administered this medicine daily for 10 days. Survival rates were increased by the pretreatment in mice inoculated i.v. with bacteria 1 day after the last administration and in mice inoculated i.p. 4 days after the last administration. After an i.v. inoculation of L. monocytogenes, the numbers of bacteria in the spleen and liver increased gradually to kill mice by day 5 in untreated group but the bacterial numbers increased slightly by day 3 and decreased from day 3 to day 8 in Hochu-ekki-to pretreated group. After an i.p. inoculation, the number of bacteria in the peritoneal cavity decreased very rapidly within 6h in Hochu-ekki-to treated group compared to that in untreated group. After the administration, number of polymorphonuclear cells increased in the peripheral blood, peritoneal cavity and spleen. In treated mice, macrophages increased in number in the peritoneal cavity and the spleen but decreased in the peripheral blood. Peritoneal macrophages from treated mice showed an enhanced activity to kill L. monocytogenes in vitro within 60 min after ingestion of bacteria. Hochu-ekki-to may augment the host defense against L. monocytogenes through the activation of macrophage series during an early phase of infection.

Dissociated development of T cells mediating delayed-type hypersensitivity and protective T cells against Listeria monocytogenes and their functional difference in lymphokine production

CD4+ T cells mediating both delayed-type hypersensitivity (DTH) and acquired cellular resistance (ACR) were generated in mice after immunization with viable Listeria monocytogenes. In contrast, CD4+ T cells from mice immunized with killed L. monocytogenes in complete Freund's adjuvant were capable of mediating only DTH but not ACR. To determine the functional difference between T cells mediating DTH and T cells mediating ACR, we examined two different populations of T cells for profiles of lymphokine production after stimulation with a specific antigen in vitro. The production of interleukin-2 (IL-2) and IL-3 but not IL-4 was observed in both T cells mediating only DTH and those mediating DTH and ACR. In this respect, both types of T cells could be categorized into the TH1 population, and they produced macrophage chemotactic factor equally well. However, the production of gamma interferon (IFN-gamma) was observed only in T cells capable of mediating both DTH and ACR. This result was confirmed not only by an enzyme immunoassay specific for murine IFN-gamma but also by Northern (RNA) analysis for the detection of IFN-gamma mRNA. These results suggested that the TH1 population may be subdivided further into two distinct subsets and that the ineffectiveness of the killed bacterial vaccine may be partly explained by the dissociated development of T cell function.

Pathogenesis of lymphoid lesions in murine experimental listeriosis

Adult female Swiss albino mice were infected intraperitoneally or subcutaneously with Listeria monocytogenes Serovar 4b or 1/2a and killed at intervals. Thymus, spleen, Peyer's patches and a variety of lymph nodes, including the jejunal (mesenteric), mediastinal, lumbar, mandibular and superficial inguinal, were examined by histopathology and by immunocytochemistry for detection of L. monocytogenes antigen. Similar results were obtained with both Serovars and by both routes of inoculation used. In the spleen, L. monocytogenes was detected, by immunoperoxidase staining, as soon as 4 h after inoculation, inside phagocytic cells located predominantly in the marginal zone of the white pulp. This was followed by inflammation, necrosis and depletion of lymphoid cells, which extended in extreme cases to the whole organ. Inflammatory lesions diminished progressively at 5 to 6 days after inoculation. In animals dying of the infection, a severe necrotizing splenitis was present. Depletion of lymphoid cells and inflammatory changes were widespread in the lymph nodes and to a lesser extent in the Peyer's patches. An extensive necrotizing lymphadenitis was the prominent lesion in severely affected nodes. Inflammatory lesions and detection of L. monocytogenes antigen started around the venules of high endothelium. A thymus depletion, not associated with the multiplication of bacteria in the organ, was also a constant feature of the infection. This study suggests that L. monocytogenes (1) is transported to the spleen and to the lymph nodes by phagocytes, entering the organs by the marginal sinus in the spleen and by the venules of high endothelium in the lymph nodes; (2) multiplies in these cells as well as in neutrophilic granulocytes (the latter rapidly migrate to the affected zones); and (3) induce a splenitis and lymphadenitis, involving predominantly T cell-dependent areas, with a necrotizing component in severe cases. From our observations it is concluded that infection of the lymphoid system is a major feature in the pathogenesis of murine listeriosis.

Macrophage chemotactic factor partially purified from granulomatous inflammation

Pathophysiological roles of macrophage chemotactic factor (MCF) in granulomatous inflammation were investigated. MCF was extracted in 10 mM phosphate-buffered saline, pH 7.4, from experimentally produced epithelioid cell granulomas in the liver and skin of mice. MCF activity reached a peak in the lesions prior to the time when granulomatous inflammation became maximal. MCF was then purified from 10-week-old hepatic granulomas and 2-week-old skin lesions by gel filtration, ion exchange column chromatography, and HPLC gel filtration. MCF from either liver or skin had a molecular weight about 650 kDa. MCF from hepatic granulomas was coupled to Affi-Gel beads and transplanted subcutaneously into naive mice. In vivo macrophage chemotaxis was observed around the beads and the cells formed a sheet, but organization of macrophages into granulomas did not occur with the MCF-active fractions. Macrophage chemotaxis alone is insufficient to elicit granulomatous inflammation.

Difference in the induction of macrophage interleukin-1 production between viable and killed cells of Listeria monocytogenes

T-cell-mediated immunity to Listeria monocytogenes in mice, as determined by delayed-type hypersensitivity and acquired resistance, was induced by immunization with viable bacteria but not with killed bacteria, even when killed cells were injected in a high dose or repeatedly. T cells obtained from mice immunized with viable L. monocytogenes were readily stimulated with killed-bacterial antigens, resulting in T-cell proliferation in vitro and expression of a delayed footpad reaction in vivo. After immunization with killed-bacterial vaccine, T-cell responsiveness to interleukin 2 (IL-2) never developed but a lower level of responsiveness to IL-1 appeared later than with T cells from mice immunized with viable bacteria. When IL-1 production by macrophages was examined in vitro, viable L. monocytogenes stimulated a high level of IL-1 release while killed bacteria did not. Avirulent strains which were ineffective in the induction of T-cell mediated immunity were incapable of inducing IL-1 production as well. The impaired ability of killed bacteria to stimulate IL-1 production was confirmed by the level of IL-1 mRNA expression. These results suggested that the ineffectiveness of killed L. monocytogenes vaccine is not due to loss or lack of antigenic epitopes but may be ascribed to insufficient induction of IL-1 production in the initial stage of the immune response in vivo.

Sequential appearance of gamma/delta- and alpha/beta-bearing T cells in the peritoneal cavity during an i.p. infection with Listeria monocytogenes

To search for a potential role of T cell antigen receptor (TcR) gamma/delta-bearing cells in host-defense against Listeria monocytogenes, we analyzed the sequential appearance of gamma/delta and alpha/beta T cell in the peritoneal exudate cells (PEC) during an i.p. infection with sublethal dose (2 X 10(3) of viable Listeria organisms in mice. The PEC on day 1 after the infection consisted of 48% macrophages and 50% lymphocytes, most of which were surface IgM+ (B) cells. The number of PEC increased to the maximal level by day 3. The PEC at this stage contained an appreciable number of CD3+ T cells in addition to a large number of macrophages. Of the CD3+ cells, the proportion of CD4- CD8- cells, most of which expressed no TcR alpha/beta, increased to the maximal level on day 3 after the infection. In correlation with an increased number of CD3+ CD4- CD8- TcR alpha/beta- cells, high level of TcR gamma/delta chain gene messages was detected in the nonadherent population of the PEC on this stage. On the other hand, the PEC on day 8 contained an increased number of CD4+ CD8- and CD4- CD8+ cells which expressed TcR alpha/beta chain on their surface. These results suggest that the gamma/delta T cells precede the alpha/beta T cells in appearance during listerial infection. The gamma/delta T cells may be involved at the first line of the host-defense against Listeria.

A low degree of requirement for Ia-positive macrophages and IL 2 in the induction phase of Listeria monocytogenes-specific T cells in vitro

We have analyzed the priming process of Listeria-specific T cells using an in vitro primary culture system. Listeria-specific T cells mediating delayed footpad reaction (DFR) and acquired cellular resistance (ACR) upon passive local transfer into naive recipients were generated from non-immune mouse spleen cells when stimulated with viable Listeria monocytogenes primarily in vitro. The effectors were detected on the third day of culture, and culturing for 5 days was sufficient for the generation of effectors mediating the peak level of DFR and ACR. The requirement of T cell subsets, Ia antigen and interleukin 2 (IL 2) for inducing effectors was studied. Presence of macrophages (M phi) and their contact to T cells were required for priming of Listeria-specific T cells in vitro. The presence of Ia antigens on macrophages was absolutely required for priming, but this requirement was lower than that in secondary immune response of Listeria-specific T cells. Effectors could not be generated when L3T4+ cells were depleted, but effectors capable of conferring a full level of DFR and ACR were induced even after the depletion of Lyt2+ cells. Contribution of IL 2 to the generation of effectors during early phase of priming was not observed. IL 2 was not produced in the supernatant of the in vitro primary culture. Precursor cells of the effectors did not respond to exogenously added recombinant IL 2 (rIL 2). Some mechanisms operating in the induction phase of Listeria-specific T cells were clarified in this study.

Protective effect of a traditional Chinese medicine, xiao-chai-hu-tang (Japanese name: shosaiko-to), on Listeria monocytogenes infection in mice

Lethal effect of Listeria monocytogenes (L. monocytogenes) in mice was prevented by an intraperitoneal (ip) injection of a traditional Chinese herbal medicine, xiao-chai-hu-tang (Japanese name: shosaiko-to), 4 days before ip bacterial infection. The numbers of bacteria in the peritoneal cavity and liver were smaller in shosaiko-to-treated mice from one day after the infection. Macrophage accumulation in the peritoneal cavity after ip inoculation of L. monocytogenes was observed in both untreated and shosaiko-to-treated mice. Although rates of such increases were almost the same between both groups, the absolute number of macrophages was larger in shosaiko-to-treated than in untreated mice because of a higher level of the macrophage number at 4 days after ip injection of shosaiko-to. In untreated mice, bactericidal activity of peritoneal macrophages decreased from one day to 3 days after ip injection of killed L. monocytogenes. Such an activity was maintained at the same level from 1 to 3 days in shosaiko-to-treated mice. Augmented accumulation of macrophages and maintenance of their bactericidal activity may be main mechanisms of the augmented resistance in shosaiko-to-treated mice. Augmented resistance against bacterial growth in the thigh muscle in ip shosaiko-to-treated mice may be caused by such mechanisms. The effect of shosaiko-to observed at an early stage of infection may be T cell-independent, since such an effect was observed in athymic nude mice and delayed footpad reaction could not be detected at such a timing in euthymic normal mice.