Activity Of Spleen Cells Research Articles

In VitroAugmentation of Natural Killer Activity and Interferon-γ Production in Murine Spleen Cells withAgaricus blazeiFruiting Body Fractions

Aqueous extracts of the Agaricus blazei fruiting body prepared at different temperatures were fractionated by ethanol precipitation with various ethanol concentrations. The original aqueous extracts of A. blazei failed to stimulate natural killer (NK) cell activity in murine spleen cells in vitro, but the strongest effect was observed in a 30% ethanol-soluble-50% ethanol-insoluble fraction prepared from the extract at 40 degrees C (fraction A-50). Fraction A-50 also showed the strongest augmenting effect on interferon (IFN)-gamma production. This augmentation of NK activity and IFN-gamma production by fraction A-50 was completely abrogated by a heat treatment.

経皮的磁気刺激の印加がマウス腫ようおよび免疫機能に与える影響

We investigated the effects of repetitive magnetic stimulation on tumor development processes and immune functions. A circular coil (inner diameter = 15 mm, outer diameter = 75 mm) was used in experiments. The stimulus conditions were as follows: peak magnetic field = 0.25 T (at the center of the coil), frequency = 25 pulses/sec, 1000 pulses/sample/day. Magnetically induced eddy currents in mice = 0.25 T: 0.79−1.54 A/m2. B16-BL6 melanoma model mice were exposed to the magnetic stimulation for 16 days from the day after the injection of cancer cells. Tumor growth study revealed a significant decrease in the tumor weight of the stimulated group (56% vs. a sham group, 41% vs. a controls). B16-BL6 cells were also exposed to the magnetic stimulation (1000 pulses/sample). However, magnetically induced eddy currents had no effect on B16-BL6 cell viabilities. Contrary to the cell viability study, proliferation activities of mice spleen cells were up-regulated by the magnetic stimulation. TNF-α production was also activated in the stimulated mice. These results indicate that the immune functions were up-regulated by the magnetic stimulation, resulting in decreased tumor weight in the tumor model mice. And they also show the potential for therapeutic use of magnetic stimulation in cancer treatment.

Balance of proliferation and cell death between thyrocytes and myofibroblasts regulates thyroid fibrosis in granulomatous experimental autoimmune thyroiditis (G-EAT)

Severe granulomatous experimental autoimmune thyroiditis (G-EAT), which progresses to fibrosis, is induced in DBA/1 mice by adoptive transfer of mouse thyroglobulin-primed and -activated spleen cells. There is extensive destruction of thyrocytes and inflammatory cell infiltration including T cells, macrophages, neutrophils, and myofibroblasts (myofbs). Suppression of transforming growth factor-beta (TGF-beta) and deficiency of interferon-gamma (IFN-gamma) inhibit fibrosis, and inflammation eventually resolves. Thyrocyte destruction in wild-type (WT) mice was a result of apoptosis, as many deoxynucleotide triphosphate nick-end labeling + apoptotic thyrocytes were present in these thyroids. The balance of apoptosis and proliferation between thyrocytes and myofbs may be important factors determining the outcome of inflammation to fibrosis versus resolution. Apoptosis and proliferation in thyrocytes versus myofbs were evaluated by dual-staining of cell-proliferating marker (Ki-67) or in situ cell death and cytokeratin or alpha-smooth muscle actin and were analyzed by confocal microscopy. Apoptotic and antiapoptotic molecules in G-EAT thyroids were detected by immunostaining. In WT thyroids, which develop fibrosis, only a few myofbs were apoptotic, and many myofbs were Ki-67+, Fas-associated death domain protein-like interleukin-1beta-converting enzyme-like inhibitory protein (FLIP)+, and Bcl-XL+. In contrast, proliferation was predominant on thyrocytes of IFN-gamma-/- mice or anti-TGF-beta-treated WT mice. These results indicate that apoptosis of inflammatory cells and regeneration of thyrocytes in IFN-gamma-/- mice and anti-TGF-beta-treated WT mice may limit development of fibrosis, whereas excessive proliferation of myofbs and loss of thyrocytes in WT mice may contribute to fibrosis.

Immune response induced by New World Leishmania species in C57BL/6 mice

In the present study, C57BL/6 mice were inoculated with metacyclic Leishmania amazonensis or L. braziliensis promastigotes. While these animals were capable of controlling the infection by L. braziliensis, they developed chronic lesions with elevated numbers of parasites when infected by L. amazonensis. The differences in parasite control were associated with a decreased production of IFN-gamma and TNF by lymph node cells from L. amazonensis-infected mice. Furthermore, these animals presented decreased spleen cell proliferation and activation of germinal centers. In addition, we compared the ability of these parasites to hydrolyze extracellular ATP and AMP. While the ATPase activity of both parasite species was similar, L. amazonensis promastigotes presented higher AMP hydrolytic activity. This increased activity may lead to an increased production of adenosine, which has been shown to present anti-inflammatory activity and may thus be involved in the establishment of the immunosuppression observed in mice infected by L. amazonensis.

Characterization of a human REL-estrogen receptor fusion protein with a reverse conditional transforming activity in chicken spleen cells.

Overexpression of the human REL transcription factor can malignantly transform chicken spleen cells in vitro. In this report, we have created and characterized a cDNA encoding a chimeric protein (RELDelta424-490-ER) in which sequences of a highly transforming REL mutant (RELDelta424-490) are fused to the ligand-binding domain of the human estrogen receptor (ER). Surprisingly, RELDelta424-490-ER is constitutively nuclear in A293 cells, and RELDelta424-490-ER activates transcription in the absence, but not in the presence, of estrogen in kappaB-site reporter gene assays. Furthermore, RELDelta424-490-ER transforms chicken spleen cells in the absence of estrogen, but the addition of estrogen blocks the ability of RELDelta424-490-ER-transformed cells to form colonies in soft agar, even though estrogen induces increased nuclear translocation of RELDelta424-490-ER in these cells. ERalpha can also inhibit REL-dependent transactivation in trans in an estrogen-dependent manner, and ERalpha can interact with REL in vitro. Thus, the RELDelta424-490-ER fusion protein shows an unusual, reverse hormone regulation, in that its most prominent biological activities (transformation and transactivation) are inhibited by estrogen, probably due to an estrogen-induced interaction between the ER sequences and sequences in the Rel homology domain. Nevertheless, these results indicate that the continual activity of REL is required to sustain the transformed state of chicken spleen cells in culture, suggesting that direct and specific inhibitors of REL may have therapeutic efficacy in certain human lymphoid cancers.

Antitumor effects of the partially purified polysaccharides from Antrodia camphorata and the mechanism of its action

Antrodia camphorata is a popular folk medicine that has attracted great attention due to its fame for antitumor activity against cancer. However, there is little information available about its action. In the present study, we purified a unique polysaccharide component from A. camphorata mycelia ( AC-PS) and found that it has pronounced anti-tumor effects on both in vitro and in vivo model. Our results showed that AC-PS alone did not show any direct cytotoxic effect to human leukemic U937 cells, even at high concentration (200 μg/ml). However, it could inhibit the proliferation of U937 cells via activation of mononuclear cells (MNCs). Treatment of U937 cells with AC-PS-stimulated-MNC-CM could significantly inhibit its proliferation with 55.3% growth inhibition rate. The in vitro antitumor activity was substantiated by the in vivo therapeutical study of AC-PS in sarcoma 180-bearing mice. Intraperitoneal and oral administration of AC-PS, 100 and 200 mg/kg significantly suppressed the tumor growth with the inhibition rate of 69.1% and 58.8%, respectively. In vivo studies also showed that several immunoparameters, such as the spontaneous proliferation of spleen cells, after AC-PS administration, were two-fold higher than in control mice. Furthermore, the cytolytic activity of spleen cells also increased from 9.8 ± 1.1% in control mice to 34.2 ± 5.5% and 48.2 ± 2.5%, after oral and intraperitoneal treatment, respectively. Besides, the mice serum interleukin-12 levels increased significantly by AC-PS treatment. Considering all these results, it is suggested that AC-PS elicit its anti-tumor effect by promoting a Th1-dominant state and killer activities.

Co-expression of interleukin-2 to increase the efficacy of DNA vaccine-mediated protection in coxsackievirus B3-infected mice

DNA immunizations with the major structural protein VP1 of coxsackievirus B3 (CVB3) have been previously found to protect mice from a lethal challenge with CVB3. The function of this vaccination procedure is mainly based on accelerated antibody induction with an early cytokine expression and increased virus-specific cytotoxic activity of spleen cells causing decreased myocyte destruction and reduced viral replication. Here, we report that the co-expression of the immune-stimulatory interleukin-2 (IL-2) can increase the efficacy of the inoculated DNA vaccine depending on the route of administration and the mouse strain used.

Intranasal delivery of chitosan–DNA vaccine generates mucosal SIgA and anti-CVB3 protection

Coxsackievirus B3 infections are common causes of acute and chronic myocarditis with no effective prophylactic treatment available. We describe here a prophylactic strategy using chitosan–DNA intranasal immunization to induce CVB3 specific immune responses. Intranasal administration with chitosan–DNA complex prepared by votexing DNA with chitosan, a natural mucus absorption enhancer, resulted in transgenic DNA expression in mouse nasopharynx. Mice immunized with chitosan–DNA (pcDNA3-VP1) encoding VP1, major structural protein of CVB3, produced much higher levels of serum IgG and mucosal secretory IgA compared to mice treated with pcDNA3-VP1 or pcDNA3. Increased virus-specific cytotoxic activity of spleen cells derived from chitosan–DNA vaccinated mice was also determined. Chitosan-pcDNA3-VP1 intranasal immunization resulted in 42.9% protection of mice against lethal CVB3 challenge and a significant reduction of viral load after acute CVB3 infection. Meanwhile no myonecrosis or infiltrating immune cells indicating ongoing myocarditis was detected in hearts of surviving mice treated with chitosan–DNA. Together, Our data show that intranasal delivery of chitosan–DNA vaccine successfully induced mucosal SIgA secretion and might be a promising vaccine candidate to protect against CVB3 infection.

Antitumor effects of fusions composed of dendritic cells and fibroblasts transfected with genomic DNA from tumor cells.

Based on several previous studies indicating that transfection of genomic DNA can stably alter the character of the cells that take up the exogenous DNA, we investigated antitumor immunity conferred by fusions of syngeneic dendritic cells (DCs) and allogeneic fibroblasts (NIH3T3) transfected with genomic DNA from B16 tumor cells. Fusion cells (FCs) composed of dendritic and genetically engineered NIH3T3 cells were prepared with polyethylene glycol, and fusion efficiency was 30.3%. Prior immunization with FCs prevented tumor formation upon challenge with B16 tumor cells. Efficacy was reduced when studies were performed in mice depleted of NK cells. Vaccination with FCs containing DCs and fibroblasts transfected with denatured DNA did not inhibit tumor growth. Cytotoxic T cell (CTL) activity of spleen cells from immunized mice against both Yac-1 and tumor cells was also stimulated by administration of FCs compared with the activity observed for cells obtained from naïve mice. These data demonstrate the therapeutic efficacy of fusion cell-based vaccine therapy using syngeneic DCs and allogeneic fibroblasts transfected with tumor-derived genomic DNA.

Effects of extracts from Brazilian sun-mushroom ( Agaricus blazei) on the NK activity and lymphoproliferative responsiveness of Ehrlich tumor-bearing mice

Agaricus blazei Murrill, is an edible and medicinal mushroom which is popularly consumed due to its antitumoral properties. The immunomodulatory effects of methanol (METH), dichloromethane (DM) and n-hexane (HEX) extracts of this mushroom were evaluated in Ehrlich tumor-bearing mice. Subcutaneous inoculation of Ehrlich tumor cells inhibited the natural killer (NK) activity of spleen cells (specific lysis=6.18±2.56%) compared with normal mice (17.59±7.77%). Treatment of tumor-bearing mice with the extracts for 10 days restored the natural killer activity against Yac-1 target cells and the best results were observed by treatment with the HEX extract (21.48±5.26%). Treatment of the animals with the HEX extract for 10 days was also able to stimulate the mitogen-induced lymphoproliferative activity of spleen cells. Thirty days after the treatment, all groups presented low proliferative activity. Specific antibody production was observed to be higher in the groups treated with the DM or METH extract 30 days after the treatment. Analysis of the 3 extracts by gas chromatography mass spectrum (GCMS) and magnetic nuclear resonance (MNR) showed that the HEX extract contains mainly sugar and fatty acids and that the METH extract also contains sugar and possibly amino acids.

Potentiation of cytotoxic activity in naïve and tumor-bearing mice by oral administration of hot-water extracts from Agaricus brazei fruiting bodies.

When hot-water extracts of mushroom Agaricus brazei MURRILL fruiting bodies (Agaricus extracts) were administered orally into Meth A-bearing mice, tumor growth was significantly inhibited compared with controls given water orally. Treatment with Agaricus extracts for five successive days significantly increased natural killer activity of spleen cells in naïve BALB/c mice. In Meth A-bearing BALB/c mice, Agaricus extracts enhanced the induction of antigen-specific cytotoxic T lymphocytes and interferon gamma production, indicating that Agaricus extracts potentiate cytotoxic activity in innate and adaptive immunity.

Trypanosoma cruzi induces strong IL-12 and IL-18 gene expression in vivo: correlation with interferon-gamma (IFN-gamma) production.

IFN-gamma, produced after infection with Trypanosoma cruzi, has been shown to be crucial in the determination of resistance or susceptibility. We have performed a detailed study on the expression of IFN-gamma and of the IFN-gamma-inducing cytokines IL-12 and IFN-gamma-inducing factor (IGIF)/IL-18 with regard to time course and tissue localization. IFN-gamma was present in high amounts in the serum and in the supernatants of unseparated spleen cells and isolated CD4+ and CD8+ T cells from the spleens of infected mice which were stimulated ex vivo with T. cruzi. Using the in situ hybridization technique we demonstrate that IL-12 p40 messages were expressed in the spleen and increased during infection, correlating with the expression of IFN-gamma transcripts. Furthermore, we show for the first time that the mRNA for the cytokine IL-18 was induced by a parasitic infection and that this expression increased during infection with T. cruzi. Interestingly, the message for IL-18 was produced earlier during infection and already had declined until day 38, when IFN-gamma and IL-12 p40 transcripts were optimally expressed. Surprisingly, the changes in IL-12 and IL-18 mRNA production were clearly seen only by in situ hybridization, but less clearly by quantitative reverse-transcriptase polymerase chain reaction (RT-PCR). This is possibly due to the extensive activation and proliferation of spleen cells observed during infection leading to a dilution of these specific mRNAs.

Structural characterization of the inhibitory DNA motif for the type A (D)-CpG-induced cytokine secretion and NK-cell lytic activity in mouse spleen cells.

Oligodeoxynucleotides (ODN) with the CpG motif have been shown to be potent stimulators of innate immunity. A theoretical concern is that uncontrolled stimulation of the innate immune system through the TLR-9 receptor could induce, or worsen, some autoimmune diseases such as adjuvant arthritis or systemic lupus erythematosus. Safe therapeutic use of such ODN could be enhanced if one could regulate some of their stimulatory activities. We have designed a group of synthetic ODNs, which were able to inhibit the induction of NK lytic activity, IL-12p40 and IFN-gamma cytokine secretion by type A (D)-CpG-ODNs. Inhibition occurred in both DNA-sequence and dose-dependent fashion. Fifty percent inhibition was achieved with ~10-nM concentration of the most potent inhibitory ODNs. Delayed addition of these ODNs for up to 2 h was still able to profoundly affect CpG-induced IL-12p40 production at 18 h. Inhibitory DNA motif consists of two nucleotide triplets, a proximal pyrimidine-rich CCT sequence and a more distal GGG triplet. Optimal distance between these blocks is between three to five nucleotides. The linker sequence between the CCT and GGG blocks can additionally modify the activity of inhibitory ODNs, in both a positive and in negative way. When the order of CCT and GGG blocks is reversed, inhibition is completely lost. These findings suggest that CpG regulation of innate immunity can itself be regulated by particular motifs, which could be of therapeutic benefit in autoimmune diseases.

Mice intranasally immunized with a recombinant 16-kilodalton antigen from roundworm Ascaris parasites are protected against larval migration of Ascaris suum.

Protective immunity to the pig roundworm, Ascaris suum, has been demonstrated by immunization of pigs with antigens derived from the parasite's larval stages. We identified a protective antigen commonly expressed in the human and pig Ascaris infections as a 16-kDa protein (As16), which has no similarity at the amino acid level to mammalian proteins but has some similarity to those of the filarial parasites and Caenorhabditis elegans gene product. Localization analysis revealed that the native As16 was highly expressed in the adult worm intestine, hypodermis, and cuticles. In addition, As16 was detected in the parasite excretory and secretory products. Mice intranasally vaccinated with Escherichia coli-expressed recombinant As16 (rAs16), coupled with cholera toxin B subunit, generated a significant increase in the level of rAs16-specific immunoglobulin G (IgG) and IgE in serum. Mucosal IgA levels were also increased. The recombinant protein evoked a mixed (both Th1 and Th2) type of immune response characterized by elevated levels of gamma interferon and interleukin-10 in the culture supernatants of activated spleen cells. An increased level of IgG1 and IgG2a in serum was also observed. The vaccinated mice showed a reduction by 58% in the recovery of challenged larvae compared to a nonvaccinated control. These results suggest the possibility of developing a mucosal vaccine for human and pig ascariasis.

Immunostimulatory effects of plasmid DNA and synthetic oligodeoxynucleotides.

Nucleic acid immunization is a new vaccination technology. DNA vaccines do not only carry the genetic information for the antigen of interest but also deliver an adjuvant effect due to the presence of immunostimulatory sequences within the plasmid backbone. It is generally assumed that the adjuvant properties of plasmid DNA are equal to those described for oligodeoxynucleotides (ODN) containing immunostimulatory CpG motifs. To challenge this hypothesis we have carried out a series of experiments comparing the ability of single- and double-stranded ODN containing CpG motifs to induce the activation of mouse spleen cells. Moreover, we compared the immunostimulatory properties of plasmids that were modified by the addition of two to four CpG motifs. Our results establish that plasmid DNA express their adjuvanticity as either double or single strands, and no differences were observed between modified and unmodified plasmids. On the other hand, the strongest stimulatory ODN sequences lost their adjuvant properties when administered as double-strand DNA. Furthermore, the profile of cytokines induced on spleen cells by plasmid DNA and ODN is different. Strikingly, plasmid DNA induces a moderate synthesis of IL-6 and a strong synthesis of IFN-gamma, whereas stimulation with ODN showed an inverse profile with a higher increase in the synthesis of IL-6 but a moderate increase in IFN-gamma. Finally, in vivo studies were consistent with the results obtained in vitro. Mice immunized with modified or unmodified plasmids encoding the glycoprotein D of HSV showed similar levels of cellular and humoral immune responses.

High antigen dose and activated dendritic cells enable Th cells to escape regulatory T cell-mediated suppression in vitro.

CD4+CD25+ regulatory T cells (Tregs) are critical for peripheral tolerance and prevention of autoimmunity. In vitro coculture studies have revealed that increased costimulation breaks Treg-mediated suppression in response to anti-CD3 or antigen. However, it was unclear whether loss of suppression arose from inactivation of Tregs or whether increased stimulation caused Th cells to escape suppression. We have investigated conditions that allow or override Treg-mediated suppression using DO11.10 TCR-transgenic T cells and chicken ovalbumin peptide 323-339-pulsed antigen-presenting cells. Treg suppression of Th proliferation is broken with potent stimulation, using activated spleen cells and high antigen dose, but is intact at low antigen dose. Costimulation with CD80 and CD86 expressed on activated dendritic cells was essential for Th cell escape from suppression at a high antigen dose. Potently stimulated Tregs were functional since they reduced levels of IL-2, IFN-gamma, IL-4 and Th CD25 expression in cocultures. Furthermore, Tregs responding to high antigen dose and activated splenocytes retained the ability to suppress proliferation, but only of Th cells responding to a sub-optimal dose of independent antigen. Together, our results demonstrate that under conditions of strong antigen-specific stimulation, Tregs remain functional, but Th cells escape Treg-mediated suppression.

An overview of the role of iron in T cell activation

AbstractIron, an essential growth trace element, is required for proliferation of all living cells, including T lymphocytes. Many, though not all, immune responses require lymphocyte proliferation. Iron deficiency, a worldwide public health problem for children and for women of childbearing age, is associated with impaired lymphocyte proliferative responses to mitogens and cell‐mediated immunity. However, the mechanisms have not been fully elucidated. Our data on certain early key events in the T cell activation pathways, obtained from iron‐deficient murine splenic T lymphocytes, show reductions in hydrolysis of cell membrane phosphatidyl inositol 4,5 bisphosphate, protein kinase C activation, and interleukin‐2 secretion. Although the expression of CD3 molecule (a component of the T cell‐receptor/CD3 complex, required for T cell activation) is not decreased by iron deficiency in splenocytes and thymocytes, the expression of the co‐stimulatory molecule, CD28, is. Iron‐deficiency increases the percentage of CD3+/CD28− thymocytes but decreases that of CD3−/CD28+ cells. Iron deficiency and iron chelation by deferoxamine decrease CD28 fluorescence intensity but tends to increase that of CD3. Progression of activated spleen cells through the cell cycle (Go/G1, S, G2/M phases) is also altered by iron deficiency independently of differences in the percentages of CD3+ T cells between groups, probably through impaired transition of G1 to S phase. Data suggest that the role of iron in T cell proliferation is not limited to the regulation of ribonucleotide reductase activity, but also involves other steps in the T cell activation pathways. J. Trace Elem. Exp. Med. 16:219–225, 2003. © 2003 Wiley‐Liss, Inc.

Polychlorinated Biphenyl-Induced Apoptosis of Murine Spleen Cells Is Aryl Hydrocarbon Receptor Independent but Caspases Dependent

Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants and many of their toxic effects, including their immunotoxicities, are mediated by the activation of aryl hydrocarbon receptor (AhR). We previously reported that Aroclor 1254, one of the most widely used PCB mixtures, increased DNA fragmentation in mouse spleen cells, suggesting that apoptosis was correlated with the immunotoxicity of PCB (Yoo et al., Toxicol. Lett. 91, 83–89, 1997). In the present study we investigated the mechanism by which PCB induces apoptosis and the involvement of AhR in the PCB-mediated apoptosis of mouse spleen cells. Aroclor 1254 induced DNA fragmentation without AhR activation, and the apoptosis was unaffected by α-naphtoflavone, a well-known antagonist of AhR. Moreover, the PCB congeners (PCB 47, 52, 128, and 153), which have little affinity for AhR, induced DNA fragmentation, whereas congeners (PCB 77, 126, and 169) that have high affinity for AhR did not induce fragmentation. The di-ortho form of PCB (PCB 153) and Aroclor 1254 induced DNA fragmentation in the spleen cells of both AhR knockout mice and Ah low-response mice, whereas the non-ortho form of PCB (PCB 126) did not induce DNA fragmentation. In the light of these findings, it is evident that AhR is not involved in PCB-mediated apoptosis. PCB 153 significantly increased caspase-3 activity in both spleen cells and human leukemia cells, and z-VAD-fmk, a general inhibitor of caspases, prevented PCB-induced DNA fragmentation. Based on our findings, the most likely mechanism that can account for this biological effect involves the induction of caspase-dependent apoptotic cell death.

ABSENCE OF SEASONAL EFFECT ON THE IMMUNOMODULATORY ACTION OF BRAZILIAN PROPOLIS ON NATURAL KILLER ACTIVITY

Propolis, a beehive product widely used in folk medicine as an antiinflammatory agent, has been attracting researchers' attention to scientifically elucidate its biological properties and therapeutic activities. The aim of this paper was to study the possible effect of propolis on natural killer activity, since propolis immunomodulatory action has been suggested, especially on non-specific immunity. Propolis was produced by africanized honeybees (Apis mellifera L.), collected throughout a whole year, and pooled by season. Hydroalcoholic solutions of propolis were prepared with each pool and administered to rats by gavage over three days. Natural killer activity of non-adherent spleen cells was evaluated by the 51Cr-release cytotoxicity assay against Yac-1 target cells. Our results indicated that the natural killer activity was increased in spleen cells from propolis-treated animals. There were no significant differences related to the seasonal effect on the immunomodulatory action of propolis.

Biological Activities of Lactobacillus casei through the Regula-tion of the Host Immune Function

Lactobacillus casei Shirota (LcS), a strain of lactic acid bacteria, has been investigated for biological activity over many years. Recently it was revealed that LcS has potent antitumor and antimetastatic effects in rodents: An intrapleural injection of LcS effectively inhibits tumor growth in the thoracic cavity in mice, resulting in prolonged survival and an improved quality of life (QOL). These activities were dependent on the stimulation of the production of several cytokines such as interferon-y, interleukin-12, and tumor necrosis factor-a. It was suggested that LcS induces a Th1 response rather than a Th2 response. As a result of this action, the inhibition of ovalbumin-specific immunoglobulin E production in the LcS-treated group was evident, compared with the response in the control group. Also, an oral administration of LcS significantly delayed the onset of carcinogenesis in mice treated with 3-methylcholanthrene and restored T cell responses such as concanavalin A-induced T cell proliferation and interleukin-2 production. Moreover, it was demonstrated that an oral administration of LcS enhanced the natural killer cell activity of spleen cells. These observations indicate that LcS affects innate immunity and augments the natural resistance of the host. Taken together, the results suggest that LcS has the potential to ameliorate or prevent a variety of diseases through a modulation of the host's immune system, specifically cellular immune responses.