Increased production of cytotoxic macrophage progenitors by Lactobacillus casei in mice

Probiotic Lactobacillus-induced improvement in murine chronic inflammatory bowel disease is associated with the down-regulation of pro-inflammatory cytokines in lamina propria mononuclear cells

IL-6/STAT-3 signals play key roles in inflammatory bowel disease (IBD). It is known that Lactobacillus casei strain Shirota (LcS) improves inflammatory disorders. This study aimed to elucidate the effect of LcS on murine chronic IBD and to clarify the mechanism. We focused the inhibitory effect of LcS on the production of IL-6 in lipopolysaccharide (LPS)-stimulated large intestinal lamina propria mononuclear cells (LI-LPMC) isolated from mice with chronic colitis and in RAW264.7 cells in vitro. We also determined in vivo the effect of LcS on murine chronic IBD models induced with dextran sodium sulphate and SAMP1/Yit mice. Finally, we examined the cellular determinants of LcS for the down-regulation of IL-6 secretion by LI-LPMC, RAW264.7 cells and peripheral blood mononuclear cells (PBMC) derived from patients with ulcerative colitis (UC). LcS, but not other strains of Lactobacillus, inhibited the production of IL-6 in LPS-stimulated LI-LPMC and RAW264.7 cells, down-regulating the nuclear translocation of NF-kappaB. The LcS-diet-improved murine chronic colitis is associated with the reduction of IL-6 synthesis by LI-LPMC. LcS also improved chronic ileitis in SAMP1/Yit mice. The release of IL-6 in vitro in LPS-stimulated LI-LPMC, RAW 264.7 cells and UC-PBMC was inhibited by a polysaccharide-peptidoglycan complex (PSPG) derived from LcS. This probiotic-induced improvement in murine chronic inflammatory bowel disease is associated with the down-regulation of pro-inflammatory cytokines such as IL-6 and IFN-gamma production in LPMC. Therefore, LcS may be a useful probiotic for the treatment of human inflammatory bowel disease.

Strain-dependent induction of cytokine profiles in the gut by orally administered Lactobacillus strains

Different Lactobacillus strains are frequently used in consumer food products. In addition, recombinant lactobacilli which contain novel expression vectors can now be used in immunotherapeutic applications such as oral vaccination strategies and in T cell tolerance induction approaches for autoimmune disease. Both for food and clinical applications of lactobacilli, proper selection of wild type strains is crucial. For that purpose, eight different common Lactobacillus strains were analysed with respect to mucosal induction of pro- and anti-inflammatory cytokines, IgA-producing plasma cells in the gut, as well as systemic antibody responses against a parenterally administered antigen. Immunohistochemical analysis of cytokine-producing cells in the gut villi showed no significant induction of the cytokines IL-1alpha, IFN-gamma, IL-4 or IL-10 after oral administration of wild type Lactobacillus strains. In contrast, oral administration of L. reuteri and L. brevis induced expression of the proinflammatory/Th1 cytokines TNF-alpha, IL-2 and/or IL-1beta. Oral administration of these two strains and L. fermentum also significantly enhanced the IgG response against parenterally administered haptenated chicken gamma globulin (TNP-CGG). The five other strains did not show this adjuvanticity. L. reuteri induced relatively high levels of IgG2a compared to L. murines, a nonadjuving Lactobacillus strain. These findings imply that different Lactobacillus strains induce distinct mucosal cytokine profiles and possess differential intrinsic adjuvanticity. This suggests that rational Lactobacillus strain selection provides a strategy to influence cytokine expression and thereby influence immune responses.

Prevention of B220+ T cell expansion and prolongation of lifespan induced by Lactobacillus casei in MRL/lpr mice

We examined the therapeutic effect of heat-killed Lactobacillus casei (LC) on MRL/lpr mice. Ingestion of a diet containing 0.05% (w/w) LC from the weaning period prolonged the lifespan and tended to reduce the proportion of B220+ T cells in the spleen and mesenteric lymph nodes (MLN) of MRL/lpr mice. When LC was intraperitoneally injected once a week after the age of 8 weeks, I-A- macrophages accumulated in the spleen as well as the peritoneum and macrophage progenitors increased in the bone marrow. Moreover, the amount of IL-6 mRNA in peritoneal macrophages was reduced by LC injection. Splenocytes from LC-injected MRL/lpr mice exhibited lower proliferative responses to mitogens than those from control MRL/lpr mice and the increase in number of B220+ T cells in the spleen and MLN was prevented by LC injection. However, LC injection affected neither expression of interferon-gamma (IFN-gamma) and IL-4 mRNAs nor proliferative capacities of splenic T cells. Our findings demonstrate that LC injection accelerates macrophage recruitment and prevents the expansion of B220+ T cells without affecting the functions of T cells in MRL/lpr mice. These immunological modulations induced by LC may lead to prolongation of the lifespan of MRL/lpr mice.

Prevention of indigenous infection of mice with Escherichia coli by nonspecific immunostimulation

We have previously reported that the lethal toxicity of 5-fluorouracil (5-FU) in specific-pathogen-free mice is due to an intestinal infection with indigenous Escherichia coli induced by the drug (K. Nomoto, T. Yokokura, Y. Yoshikai, M. Mitsuyama, and K. Nomoto, Can J. Microbiol. 37:244-247, 1991). In the present study we demonstrate that nonspecific immunostimulation is effective in the protection of mice from the lethal indigenous infection induced by 5-FU. Intravenous or subcutaneous injection of a preparation of heat-killed Lactobacillus casei YIT 9018, a potent nonspecific immunostimulant, into BALB/c mice reduced the lethal toxicity of 5-FU at doses ranging from 338 to 800 mg/kg of body weight if YIT 9018 was injected 7 to 40 days before administration of 5-FU. Systemic infection with E. coli developed in all of the 5-FU-treated control mice 7 days or more after administration of 5-FU in large doses and was accompanied by overgrowth of the bacteria in the intestinal tract. Pretreatment of mice with YIT 9018 resulted in a decreased occurrence of systemic infection with E. coli to levels of 0 to 20% and no significant changes in the population levels of E. coli in the intestinal tract during the 14 days after administration of 5-FU. The levels of leukopenia in the spleen and peripheral blood were lower, and recovery of granulocyte-macrophage precursor cells in the spleen and femur began earlier in the treated animals than in the 5-FU-treated controls. Intravenous transfusion of syngeneic normal bone marrow cells or spleen cells into the mice at an early period after administration of 5-FU diminished markedly the occurrence of the lethal indigenous infection, suggestion that an earlier recovery from chemotherapy-induced myelosuppression is important in the mechanisms of protection of the host from the infection.

Possible mechanism of the preventive effect of BCG against diabetes mellitus in NOD mouse. II. Suppression of pathogenesis by macrophage transfer from BCG-vaccinated mice

Our previous reports showed that a single injection of live BCG, one of the biological response modifiers, prevents insulitis and overt diabetes in NOD mice and that the suppression could be due to the generation of some type of suppressor cells in the BCG-treated mice. Furthermore, a more recent study has revealed that macrophages suppressive against a variety of lymphocyte functions can be induced by BCG, which suggests that these macrophages are involved in the suppression of the pathogenesis. To obtain valid evidence for this speculation, the effects of transfer of macrophage and T-cell fractions on the pathogenesis were examined in the present study. Transfer of macrophage-enriched spleen cell fraction harvested from the BCG-treated females to young females abolished the occurrence of spontaneous diabetes up to the age of 25 to 30 weeks. Also, macrophage transfer prevented the progress of insulitis. In contrast, transfer of a T-cell-enriched fraction did not suppress insulitis and overt diabetes. From these results, it could be concluded that the suppression of the autoimmune pathogenesis of diabetes by BCG is due to the generation of suppressor macrophages.

Modulation of alloreactivity by Mac-1+, -2+, and -3+ macrophages from normal and tumor-bearing hosts: flow cytofluorometrically separated macrophages

Macrophages (M phi) are multifunctional cells that regulate humoral and cellular immune responses. Our studies of tumor-induced M phi-mediated dysfunction used M phi subsets which were defined by their Mac-1, Mac-2, and Mac-3 surface markers. To measure the accessory activity of M phi for T cell alloreactivity, thioglycollate-elicited peritoneal M phi from normal and tumor-bearing hosts (TBH) were labeled with anti-Mac-1, -2, or -3 antibodies and separated by flow cytofluorometry. The separated Mac-1+, -2+, and -3+ M phi were called sorted M phi, while unseparated M phi were designated unsorted M phi. Both M phi types were added to mixed lymphocyte reaction (MLR) cultures at concentrations ranging from a low of 2% M phi to a high of 20% M phi. The low concentration of unsorted normal host M phi caused a 31% suppression of alloreactivity. Suppression reached 68% when high concentrations of unsorted normal host M phi were added to the MLR cultures. Unsorted TBH M phi reduced alloreactivity by 64% and 86% at low and high concentrations, respectively. When separated into subpopulations, normal host Mac-1+ M phi reduced alloreactivity by 48% and 81% when added at low and high concentrations, respectively. TBH Mac-1+ reduced alloreactivity by 31% and 59% at low and high concentrations, respectively. There were no differences in the suppression caused by normal or TBH Mac-2+ M phi, and by normal or TBH Mac-3+ M phi. Indomethacin treatment did not effect the suppression caused by Mac-1+ M phi, suggesting that proataglandin E2 was not involved. Indomethacin treatment did reduce suppression mediated by Mac-2+, -3+, and unsorted M phi. Mac-2+ M phi dramatically enhanced alloreactivity at low concentrations with normal host Mac-2+ M phi providing greater enhancement of alloreactivity than TBH Mac-2+ M phi. The division of M phi into subpopulations on the basis of Mac antigens suggested that Mac-1+ and -3+ M phi played a major role in immunosuppression in the normal host, while Mac-3+ M phi were more active in TBH immunosuppression. Because no one population of sorted TBH M phi was more suppressive than sorted normal host M phi, we suggest that tumor-induced immunosuppression may involve a network of suppressor M phi.

Normal and tumor-bearing host splenic macrophage responses to lipopolysaccharide

Lipopolysaccharide (LPS) was used to assess the responses of normal and tumor-bearing host (TBH) macrophages (M phi) to activation signals. M phi were incubated with LPS for either 3 hr or 24 hr and then assayed for phenotypic, functional, or cell-cycle changes. A 3-hr LPS treatment had no significant effect on M phi phenotype. In contrast, the 24-hr LPS treatment caused a significant decrease in the percentage of normal host Mac+ and Ia+ M phi. In the TBH, a 24-hr LPS treatment caused an increase in the percentage of Mac-1+ and -2+ M phi and a decrease in the percentage of Mac-3+ and Ia+ M phi. When normal host M phi were plated for 24 hr (control), there was an increase in Mac-1+ and -2+ M phi and a decrease in Ia+ M phi. The 24-hr TBH control showed a decrease in Mac-1+ and Ia+ M phi. To assess functional changes, LPS-treated normal and TBH M phi were added to the allogeneic mixed lymphocyte reaction (MLR) or the autologous MLR (AMLR). There were no significant differences in M phi accessory activity after a 3-hr LPS treatment. A 24-hr LPS treatment of normal host M phi also had no effect. A 24-hr LPS treatment of TBH M phi led to a significant decrease in allogeneic T-cell reactivity, and even the 24-hr TBH control showed significant suppression of T-cell responsiveness. In the AMLR, a measure of autoreactive T-cell responsiveness, a 3-hr LPS treatment had no affect on normal host M phi but led to increased accessory ability in TBH M phi. TBH M phi, however, were still less than 50% as responsive as normal host M phi even after LPS treatment. The 24-hr LPS treatment caused a significant decrease in normal or TBH M phi accessory activity. A 24-hr plating of normal host M phi decreased their accessory ability. In addition to the phenotypic and functional changes after LPS treatment, M phi cell-cycle kinetics were also investigated. The percentages of normal host M phi in G0/G1 were not changed significantly after a 3-hr LPS treatment. In contrast, M phi plated for 24 hr with or without LPS had a decreased percentage of cells in G0/G1. Normal host M phi showed little change in total RNA levels after a 3-hr treatment but had increased RNA levels after a 24-hr treatment.(ABSTRACT TRUNCATED AT 400 WORDS)

Two-color flow cytometric analysis of the expression of MAC and MHC class II antigens on macrophages during tumor growth

Tumor-bearing host (TBH) macrophages (M phi) exhibit immune dysfunction that is concomitant with phenotypic changes. We examined M phi subpopulations by changes in the expression of surface antigens Mac-1, -2, -3, and Ia on normal and TBH peritoneal and splenic M phi. M phi were double-labeled and analyzed by flow cytometry to observe multiple expression of surface antigens. Tumor growth alters the multiple expression of these M phi markers. Peritoneal and splenic M phi had different Mac+ and Mac+Ia+ population percentages. In TBH, peritoneal M phi had decreased percentages of Mac-1+2+, Mac-1+3+, Mac-2+3+, and Mac+Ia+ M phi. This decrease correlated with functional changes in TBH M phi. In contrast, there was an increase in Mac-2-Ia- TBH peritoneal M phi. Previously undiscovered Mac-1+2-3- and Mac-1-2-3+ populations were found. In contrast to peritoneal M phi, there was an increase in the percentage of Mac-1+2+, Mac-1+3+, and Mac-2+3+ splenic TBH M phi but, like peritoneal M phi, there was a decrease in the percentage of Mac+Ia+ M phi. Also, TBH splenic M phi showed a smaller but more uniform antigen density than normal host splenic M phi. Tumor growth modulated phenotypic alterations in peritoneal and splenic M phi subpopulations. Combined with earlier functional studies of M phi subpopulations, these data suggested a relationship between changes in M phi phenotype and tumor-induced dysfunction of M phi-modulated immune activity.