The augmentative effect of a protein-bound polysaccharide (PSK) on tumoricidal activity of the soluble factor produced by a streptococcal preparation (OK-432)-activated macrophages

The enhancement of antitumor activities of the tumoricidal soluble factor (SF) from a streptococcal preparation (OK-432)-activated macrophages by the pretreatment with a protein-bound polysaccharide (PSK) was investigated in tumor-bearing mice.Two-step stimulations with OK-432 atin vivo priming andin vitro eliciting were required for the production of the tumoricidal SF by macrophages, and the tumoricidal activity of the SF apparently correlated with the uptake of OK-432 by macrophages at priming phase.Tumoricidal activity of the SF from OK-432-activated macrophages in proteose-peptone (P-P)-pretreated mice significantly decreased with the development of the tumor, whereas in PSK-pretreated mice did not. Pretreatment of tumor-bearing mice with PSK saved a decrease in the macrophages carrying Ia^k or asialo GM1 antigens and an increase in wheat germ agglutinin (WGA) receptors. Furthermore, the uptake of OK-432 by macrophages at priming phase was enhanced. The tumoricidal activity of the SF from OK-432-activated macrophages was augmented.Thus, PSK may restore the depressed functions of macrophages, and the combination therapy with PSK and OK-432 may be effective to enhance the production of tumoricidal SF in tumor-bearing mice.     

Conventional alpha beta T cells are sufficient for innate and adaptive immunity against enteric Listeria monocytogenes

We have begun to dissect the cellular requirements for generation of immunity against enteric infection by Listeria monocytogenes using a novel T(-) B(-) NK(-) mouse strain (mice double deficient for the common cytokine receptor gamma-chain (gamma(c)) and the recombinase-activating gene-2 (RAG2/gamma(c) mice). Initial experiments showed that C57BL/6 mice and alymphoid RAG2/gamma(c) mice had similar kinetics of bacterial accumulation in the spleen, liver, and brain early after intragastric L. monocytogenes infection (up to day 3), calling into question the physiologic role of gut-associated lymphoid cells during the passage of this enterobacterium into the host. However, in contrast to C57BL/6 mice, RAG2/gamma(c) mice rapidly succumbed to disseminated infection by day 7. Polyclonal lymph node CD4(+) and CD8(+) alphabeta T cells were able to confer RAG2/gamma(c) mice with long-lasting protection against enteric L. monocytogenes infection in the absence of gammadelta T, NK, and NK-T cells. Moreover, these alphabeta T-reconstituted RAG2/gamma(c) mice produced IFN-gamma at levels comparable to C57BL/6 mice in response to L. monocytogenes both in vitro and in vivo. Protection was IFN-gamma dependent, as RAG2/gamma(c) mice reconstituted with IFN-gamma-deficient alphabeta T cells were unable to control enteric L. monocytogenes infection. Furthermore, alphabeta T cell-reconstituted RAG2/gamma(c) mice were able to mount memory responses when challenged with lethal doses of L. monocytogenes. These data suggest that NK, NK-T, gammadelta T, and B cells are functionally redundant in the immunity against oral L. monocytogenes infection, and that in their absence alphabeta T cells are able to mediate the early IFN-gamma production required for both innate and adaptive immunity.     

Recombinant granulocyte-macrophage colony-stimulating factor restores deficient immune responses in mice with chronic Trypanosoma cruzi infections

Spleen cells from mice with chronic Trypanosoma cruzi infection generate a minimal plaque-forming response to SRBC in vitro. Addition of granulocyte-macrophage (GM)-CSF to cultures of spleen cells from chronically infected mice restored the plaque-forming cells (PFC) response to normal levels. Splenic adherent cells from chronically infected mice were deficient in their ability to reconstitute the PFC response of accessory cell-depleted normal spleen cells. Preincubation of splenic adherent cells from infected mice with GM-CSF restored their ability to reconstitute the PFC response of adherent cell depleted cultures. Ia Ag expression by splenic adherent cells from chronically infected mice was significantly lower compared to Ia Ag expression of cells from normal mice. Incubation of splenic adherent cells from chronically infected mice for 48 h with GM-CSF increased levels of Ia Ag expression to approximately those of uninfected mice. Peritoneal macrophages from infected mice produced IL-1 after incubation with GM-CSF at levels equivalent to those produced by similarly treated control macrophages. Spleen cells from chronically infected mice showed significant induction of IL-2 mRNA after GM-CSF treatment, and the addition of the anti-IL-2 mAb to GM-CSF supplemented cultures of spleen cells from infected mice blocked the restoration of the anti-SRBC PFC response. Thus, the ability of GM-CSF to restore the anti-PFC response to SRBC appears to involve the up-regulation of accessory cell function that includes increased Ia Ag expression and the induction of IL-1 production. These events also involve increased IL-2 production with resultant up-regulation of the response to SRBC by spleen cells from infected mice. Finally, it was shown that treatment of infected mice with rGM-CSF completely restored their depressed PFC production in vivo.     

Differences in interleukin-12 and -15 production by dendritic cells at the early stage of Listeria monocytogenes infection between BALB/c and C57 BL/6 mice

The mechanisms responsible for the resistance of C57BL/6 mice and for the susceptibility of BALB/c mice to infection with Listeria monocytogenes were studied by comparing early IL-12 and IL-15 production by dendritic cells (DC) after infection with L. monocytogenes. Splenic DC expressing CD11b(low) and CD11c(+) obtained from C57BL/6 mice at 3 and 6 h after L. monocytogenes infection expressed higher levels of IL-12 p40 mRNA and IL-12 p40 protein than did those from BALB/c mice. Concurrently, a larger amount of IFN-gamma was produced by the splenic T cells from C57BL/6 mice in response to immobilized anti-TCRalphabeta mAb than by those from BALB/c mice, while the splenic T cells from BALB/c mice produced a higher level of IL-4 upon TCR alphabeta stimulation than did those of C57BL/6 mice. IL-15 mRNA and intracellular IL-15 protein were detected more abundantly in the DC from C57BL/6 mice than in those from BALB/c mice on day 3 after infection. CD3(+) IL2Rbeta (+) cells in the spleen were increased in C57BL/6 mice but not in BALB/c mice at the early stage after infection. Furthermore, IL-12Rbeta2 gene expression was up-regulated in T cells from C57BL/6 mice but not in those from BALB/c mice at the early stage after listerial infection. These results suggest that the difference in early production of IL-12 and IL-15 by DC may at least partly underlie the difference in susceptibility to L. monocytogenes between C57BL/6 and BALB/c mice.     

Modulation of lymphoproliferation and oxidative burst by herpes-transformed tumors.

In this study, herpes simplex virus Type 2 (HSV-2)-transformed cells (H238) and conditioned medium (CM) from H238 cell cultures were studied with respect to their effects on lymphoproliferation and the chemiluminescent oxidative burst of phagocytic cells. The H238 cells expressed a nuclear antigen detectable by fluorescent antibody testing using pooled sera from tumor-bearing mice, but no HSV-1 or HSV-2 cell membrane antigens could be found using specific monoclonal antibodies. BALB/c mice subcutaneously injected with 1 X 10(6) H238 cells developed progressively growing fibrosarcomas and depressed T lymphocyte blastogenesis in response to phytohemagglutinin (PHA) by 6 weeks post-injection when compared to non-injected controls. In contrast, oxygen radical production was increased by nearly 28-fold in the tumor-bearing subjects at this time. Incubation of normal mouse spleen cells in 100 microliters to 500 microliters of CM/ml resulted in significant dose-dependent suppression of PHA-induced lymphoproliferation. This was seen when the total spleen cell population was used, as well as after removal of the adherent cells, thereby suggesting that the inhibitory effect was not due to activation of adherent suppressor cells by the CM. However, the oxidative burst of total and adherent spleen cells from normal mice was significantly enhanced by the presence of either the H238 cells or their CM. In contrast, oxygen radical production by J774A.1 cells (a BALB/c mouse macrophage cell line) was depressed by H238 cells. Our results show that H238 tumors can alter lymphocyte as well as phagocytic cell functions both in vivo and in vitro. These tumor-induced modulations may occur via secretion of soluble factors or direct cell-to-cell interactions and, thus, may influence the outcome of immunotherapy in the tumor-bearing host.     

Enhanced resistance to Gram-positive bacterium and increased susceptibility to bacterial endotoxin in mice sensitized with Propionibacterium acnes: involvement of Toll-like receptor

Mice sensitized with Propionibacterium acnes showed an enhanced resistance against infection with Listeria monocytogenes in contrast to the increased susceptibility to LPS-induced endotoxin shock. The enhanced protection to L. monocytogenes was mediated by activated innate immunity but not by generation of Listeria-specific acquired immunity. After infection with L. monocytogenes, the elimination of bacteria was observed earlier in accordance with a higher level of endogenous cytokine production in P. acnes-sensitized mice than in control mice. Peritoneal cells from P. acnes-sensitized mice produced a larger amount of IL-12p70 and nitric oxide after stimulation with heat-killed L. monocytogenes or peptidoglycan purified from Staphylococcus aureus. RT-PCR analysis showed that the expression of TLR2 but not TLR1, TLR4 nor TLR6 was induced by injection of P. acnes in peritoneal cells. These results indicated that P. acnes-sensitization could induce the activation of innate immunity against L. monocytogenes through increased recognition of bacterial components by TLR2.     

Effects of murine recombinant interleukin 1 alpha on the host response to bacterial infection

The effects of exogenously administered rIL-1 alpha on elimination of viable listeriae from the liver and spleen during the course of a primary Listeria monocytogenes infection was studied. Similar numbers of L. monocytogenes were recovered from rIL-1 alpha-treated and control mice at up to 24 h after infection; however, by 48 h after infection more than 1 log10 fewer viable L. monocytogenes were recovered from the spleens of rIL-1 alpha-treated mice than from Listeria-infected controls. The difference in bacterial burden between IL-1 alpha-treated and control mice increased with time; by 7 days after infection viable L. monocytogenes had been eliminated from most rIL-1 alpha-treated mice, whereas control mice still harbored 10(4) to 10(5) L. monocytogenes per spleen and liver. Histopathologic examination confirmed that rIL-1 alpha-treated mice suffered considerably less damage to the spleen, liver, lung, and brain than did control mice. To determine whether rIL-1 alpha-mediated protection indirectly by augmenting the release of other cytokines, we determined serum levels of colony-stimulating activity and IFN activity in rIL-1 alpha-treated and control Listeria-infected mice. Treatment with rIL-alpha elicited an early burst of serum colony-stimulating activity as compared with sera from Listeria-infected control mice. These data suggest that exogenous administration of rIL-1 initiates release of colony-stimulating activity, and perhaps other cytokines, that accelerate the protective response of the infected host. Prophylactic augmentation of antimicrobial resistance by administration of rIL-1 alpha may be worthy of further evaluation.     

Protection by dexamethasone from a lethal infection with Listeria monocytogenes in mice

Abstract The effects of dexamethasone (DEX) on a lethal infection with Listeria monocytogenes were studied in mice. Mice were completely protected against the lethal infection when treated with 3.3 mg per kg of DEX. The effect was observed only when DEX was injected before infection. The control mice died from day 3 to day 5 of infection, whereas DEX-treated mice could eliminate L. monocytogenes cells from the organs by day 11 of infection. High titres of endogenous tumour necrosis factor (TNF), interleukin-6 (IL-6) and gamma interferon (IFN-γ) were induced in the bloodstreams and organs of the drug-free mice. DEX suppressed IL-6 production, but augmented TNF and IFN-γ production within 24 h of infection, whereas production of all three endogenous cytokines was suppressed in the DEX-treated mice on day 3 of infection when the control mice began to die. These results suggest that DEX shows a protective effect on a lethal infection with L. monocytogenes in mice and that regulation of production of endogenous cytokines might be involved in the effect of DEX.     

Inhibitory role of neutrophils on influenza virus multiplication in the lungs of mice.

The protective role of neutrophils on intranasal infection of influenza virus was investigated in 3 strains of tumor-bearing mice with neutrophilic leukocytosis. In vitro multiplication of influenza virus was inhibited by neutrophils from both normal and tumor-bearing mice, and the inhibitory effect of neutrophils was augmented by an addition of fMLP to the culture. Pulmonary virus infectivities in the early phase after infection decreased in such ICR and BALB/c mice, and virus elimination in the late phase was accelerated in the ICR mice. However, no decrease in pulmonary virus infectivity was observed in tumor-bearing C57BL/6 mice. Intranasal administration of fMLP into normal and tumor-bearing C57BL/6 mice after infection significantly inhibited the virus propagation in the lungs. The decrease in neutrophil infiltration into the lung in tumor-bearing C57BL/6 mice was confirmed from histological observations of the lung and lung lavage after infection and from analysis of the neutrophil chemotactic activity induced by fMLP. This might be responsible for the high level of pulmonary virus titer in tumor-bearing C57BL/6 mice. Phagocytic activities of alveolar macrophages and productions of neutralizing antibody were suppressed in the 3 strains of tumor-bearing mice. These observations indicated that neutrophils could be significant effector cells as a host defense mechanism against influenza virus infection in vivo, and infiltration and functional activation of neutrophils could play a significant role in virus elimination from the infected site. Furthermore, the inhibition of virus propagation by neutrophils in vitro was almost completely abrogated by an addition of ZnSO4, suggesting that calprotectin could inhibit influenza virus multiplication.     

Prostaglandin-mediated suppression of delayed-type hypersensitivity to infected erythrocytes during Babesia microti infection in mice

The mechanism of suppression of delayed-type hypersensitivity (DTH) to intraerythrocytic Babesia microti which occurs during infection in mice was examined. The suppression was not specific for anti-parasite DTH; infected mice immunized and challenged with sheep red blood cells had a similar depression of anti-sheep red blood cell DTH. Sublethal or lethal irradiation did not significantly alter the suppression of the DTH response, and cyclophosphamide pretreatment of infected mice also had no effect on suppression. Multiple passive transfer experiments using serum or regional lymph node cells from immunized or infected and immunized (suppressed) donor animals failed to demonstrate any ability to transfer suppression of DTH. Adherent cells from the spleens or peritoneal exudates of suppressed mice, however, did significantly depress the ability of immunized mice to express a DTH response. The cells responsible for this suppression were Thy 1- and nonspecific esterase+. Treatment of suppressive cell populations with 10 micrograms/ml indomethacin for 24 hr in vitro abrogated their suppressive ability, and in vivo administration of indomethacin to suppressed mice also restored DTH to normal levels. By examining levels of prostaglandin E2 (PGE2) in supernates of cultured peritoneal exudate cells from immune or suppressed mice, it was shown that infected mice had peritoneal exudate cells which produced significantly more PGE2 than similar cells from immune mice. These data suggest that B. microti infection elicits synthesis of PGE2 by macrophage-like cells which results in suppression of DTH to parasite as well as heterologous antigens.     

Dependency of caspase-1 activation induced in macrophages by Listeria monocytogenes on cytolysin, listeriolysin O, after evasion from phagosome into the cytoplasm

Listeriolysin O (LLO), an hly-encoded cytolysin from Listeria monocytogenes, plays an essential role in the entry of this pathogen into the macrophage cytoplasm and is also a key factor in inducing the production of IFN-gamma during the innate immune stage of infection. In this study, we examined the involvement of LLO in macrophage production of the IFN-gamma-inducing cytokines IL-12 and IL-18. Significant levels of IL-12 and IL-18 were produced by macrophages upon infection with wild-type L. monocytogenes, whereas an LLO-deficient mutant (the L. monocytogenes Deltahly) lacked the ability to induce IL-18 production. Complementation of Deltahly with hly completely restored the ability. However, when Deltahly was complemented with ilo encoding ivanolysin O (ILO), a cytolysin highly homologous with LLO, such a restoration was not observed, although ILO-expressing L. monocytogenes invaded and multiplied in the macrophage cytoplasm similarly as LLO-expressing L. monocytogenes. Induction of IL-18 was diminished when pretreated with a caspase-1 inhibitor or in macrophages from caspase-1-deficient mice, suggesting the activation of caspase-1 as a key event resulting in IL-18 production. Activation of caspase-1 was induced in macrophages infected with LLO-expressing L. monocytogenes but not in those with Deltahly. A complete restoration of such an activity could not be observed even after complementation with the ILO gene. These results show that the LLO molecule is involved in the activation of caspase-1, which is essential for IL-18 production in infected macrophages, and suggest that some sequence unique to LLO is indispensable for some signaling event resulting in the caspase-1 activation induced by L. monocytogenes.     

T cell function during fatal and self-limiting malarial infections of mice.

Delayed-type hypersensitivity (DTH) to sheep erythrocytes (SRBC) was found to be depressed during fatal Plasmodium berghei and self-limiting P. yoelii infections of mice. By testing mice presensitized to SRBC before P. berghei infection, and by transfer of cells sensitized in uninfected mice into P. yoelii-infected recipients, the immunological lesion was found to be at the level of DTH expression, rather than at the level of T cell sensitization. That acute inflammatory responsiveness is impaired during malarial infection was confirmed by testing this response to local injection of LPS in P. yoelii-infected mice. The results suggested that depressed DTH responsiveness in malarious mice is not a valid indication of impaired T cell function.     

Manipulating the rate of memory CD8+ T cell generation after acute infection

Infection with Listeria monocytogenes elicits expansion in numbers of Ag-specific CD8+ T cells, which then undergo programmed contraction. The remaining cells undergo further phenotypic and functional changes with time, eventually attaining the qualities of memory CD8+ T cells. In this study, we show that L. monocytogenes-specific CD8+ T cell populations primed in antibiotic-pretreated mice undergo brief effector phase, but rapidly develop phenotypic (CD127(high), CD43(low)) and functional (granzyme B(low), IL-2-producing) characteristics of memory CD8+ T cells. These early memory CD8+ T cells were capable of substantial secondary expansion in response to booster challenge at day 7 postinfection, resulting in significantly elevated numbers of secondary effector and memory CD8+ T cells and enhanced protective immunity compared with control-infected mice. Although early expansion in numbers is similar after L. monocytogenes infection of antibiotic-pretreated and control mice, the absence of sustained proliferation coupled with decreased killer cell lectin-like receptor G-1 up-regulation on responding CD8+ T cells may explain the rapid effector to memory CD8+ T cell transition. In addition, antibiotic treatment 2 days post-L. monocytogenes challenge accelerated the generation of CD8+ T cells with memory phenotype and function, and this accelerated memory generation was reversed in the presence of CpG-induced inflammation. Together, these data show that the rate at which Ag-specific CD8+ T cell populations acquire memory characteristics after infection is not fixed, but rather can be manipulated by limiting inflammation that will in turn modulate the timing and extent to which CD8+ T cells proliferate and up-regulate killer cell lectin-like receptor G-1 expression.     

Listeria monocytogenes infection affects a subset of Ly49-expressing NK cells in the rat

NK cells are protective against certain bacterial and viral infections, and their production of IFN-γ is important for the early innate immune defence against L. monocytogenes. We have previously shown that depletion of NK cells in rats leads to increased bacterial burden upon L. monocytogenes infection, and that a subset of NK cells encompassing the majority of Ly49 receptors (Ly49s3+ NK cells) contributed to this effect. In this study, we have further investigated how the Ly49s3+ NK cell subset is affected by L. monocytogenes infection. We observed an increased percentage of Ly49s3+ NK cells in the spleen and a reduction in the bone marrow within the first 48 hrs of L. monocytogenes infection. Concomitantly, we observed increased expression levels of the inflammatory chemokine receptors CCR5 and CXCR3 by Ly49s3+ bone marrow NK cells, as compared to Ly49s3- NK cells, suggesting involvement of Ly49s3+ NK cells in the early phase of infection. However, NK cell production of IFN-γ was independent of Ly49 receptor expression. Furthermore, we observed increased expression levels of MHC class I molecules on both macrophages and NK cells during the first 48 hrs of infection, paralleled by a reduction in the surface expression of Ly49s3 on NK cells. In conclusion, L. monocytogenes infection modulates the tissue distribution of Ly49s3+ NK cells, and induces increased MHC class I expression and hence reduced surface expression of Ly49 receptors on NK cells. These changes indicate that L. monocytogenes infection may have multiple effects on NK cells in vivo, and suggests the involvement of Ly49-expressing NK cells in the immune responses towards L. monocytogenes.     

Augmentation of delayed-type hypersensitivity by vesicular stomatitis virus infection in mice

Effects of the infection with vesicular stomatitis virus (VSV) on delayed-type hypersensitivity (DTH) to heterologous erythrocytes were investigated in mice. Infection at the time of immunization resulted in production of high levels of DTH that were specific to the antigen used for immunization. The high level of DTH produced in VSV-infected mice could not be attributed to the nonspecific enhancement of the footpad swelling with the infection. Augmentation of DTH was observed in all strains of the mouse (CBA, BALB/c, C3H/He, and C57BL/6) used. The augmenting effect of VSV infection was not as apparent in adult thymectomized mice in which the level of VSV-replicating T cells was reduced. These results strongly suggest that DTH-mediating T cells are resistant to infection by VSV, and also that there are VSV-sensitive cells that may be engaged in the suppression of DTH. It seems improbable, however, that the cells sensitive to VSV infection represent the suppressor cells themselves, since the enhancing effect was not observed in mice in which the suppressor cells were induced by the administration of high doses of the antigen.     

Ly6G+ neutrophils are dispensable for defense against systemic Listeria monocytogenes infection

Listeria monocytogenes is a facultative intracellular bacterium that causes systemic infections in immunocompromised hosts. Early recruitment of myeloid cells, including inflammatory monocytes and neutrophils, to sites of L. monocytogenes infection is essential for the control of infection and host survival. Because previous experimental studies used depleting or blocking Abs that affected both inflammatory monocytes and neutrophils, the relative contributions of these cell populations to defense against L. monocytogenes infection remain incompletely defined. In this article, we used highly selective depletion strategies to either deplete inflammatory monocytes or neutrophils from L. monocytogenes-infected mice and demonstrate that neutrophils are dispensable for early and late control of infection. In contrast, inflammatory monocytes are essential for bacterial clearance during the innate and adaptive phases of the immune response to L. monocytogenes infection.     

Inducible costimulator protein controls the protective T cell response against Listeria monocytogenes

The inducible costimulator protein (ICOS) was recently identified as a costimulatory molecule for T cells. Here we analyze the role of ICOS for the acquired immune response of mice against the intracellular bacterium Listeria monocytogenes. During oral L. monocytogenes infection, low levels of ICOS expression were detected by extracellular and intracellular Ab staining of Listeria-specific CD4(+) and CD8(+) T cells. Blocking of ICOS signaling with a soluble ICOS-Ig fusion protein markedly impaired the Listeria-specific T cell responses. Compared with control mice, the ICOS-Ig treated mice generated significantly reduced numbers of Listeria-specific CD8(+) T cells in spleen and liver, as determined by tetramer and intracellular cytokine staining. In contrast, the specific CD8(+) T cell response in the intestinal mucosa did not appear to be impaired by the ICOS-Ig treatment. Analysis of the CD4(+) T cell response revealed that ICOS-Ig treatment also affected the specific CD4(+) T cell response. When restimulated with listerial Ag in vitro, reduced numbers of CD4(+) T cells from infected and ICOS-Ig-treated mice responded with IFN-gamma production. The impaired acquired immune response in ICOS-Ig treated mice was accompanied by their increased susceptibility to L. monocytogenes infection. ICOS-Ig treatment drastically enhanced bacterial titers, and a large fraction of mice succumbed to the otherwise sublethal dose of infection. Thus, ICOS costimulation is crucial for protective immunity against the intracellular bacterium L. monocytogenes.     

Effect of N-acetylchitohexaose against Candida albicans infection of tumor-bearing mice

A water-soluble oligosaccharide, N-acetylchitohexaose (NACOS-6), was able to enhance the protective effect against Candida albicans infection in mice during the early phase of tumor-bearing. A significant decrease in the number of C. albicans cells in the kidneys of NACOS-6-treated tumor-bearing mice was observed 8 days after the fungal infection, or 15 days after the tumor transplantation. The candidacidal activity of polymorphonuclear leukocytes from NACOS-6-treated tumor-bearing mice did not differ from that of NACOS-6-untreated tumor-bearing mice. On the other hand, the candidacidal activities of both macrophages and T lymphocytes increased following administration of NACOS-6 in the early phase of tumor-bearing. The culture supernatant of T lymphocytes from NACOS-6-treated tumor-bearing mice also potentiated the candidacidal activity of casein-induced macrophages. An enhancement of natural killer cell activity of splenic lymphocytes obtained from NACOS-6-treated tumor-bearing mice was also observed.     

Efficient natural defense mechanisms against Listeria monocytogenes in T and B cell-deficient allogeneic bone marrow radiation chimeras. Preactivated macrophages are the main effector cells in an early phase after bone marrow transfer

Radiation chimeras in the early phase after bone marrow transplantation are a good model to study the efficiency of the body's nonspecific defense system represented by macrophages (M phi), polymorphonuclear cells (PMN), and NK cells. These cell types are present in large numbers in spleen and liver at that time, whereas the specific immune system represented by T and B cells is functionally deficient. We previously reported enhanced activities in vitro of M phi (and PMN) from recipient animals in an early phase after allogeneic bone marrow transfer. We here demonstrate that these activities result in enhanced spontaneous resistance against Listeria monocytogenes in vivo: CFU of L. monocytogenes in spleen and liver 48 h after infection were about 1 or 2 to 4 log steps less than in untreated control mice of donor or host haplotype. This enhanced resistance decreased over the 4-mo period after marrow transfer. Preactivated M phi were identified as the most important effector cells. Isolated from spleen and peritoneal cavity, they performed enhanced killing of phagocytosed Listeria. Such preactivated M phi occurred in recipient animals after transfer of allogeneic but not of syngeneic bone marrow. The precise mechanism of M phi activation in the allogeneic radiation chimera in the complete absence of any detectable T cell function is not clear at present. However, these preactivated M phi display an important protective effect against L. monocytogenes: chimeras could eliminate Listeria without acquisition of positive delayed-type sensitivity when infected with 10(3) bacteria. An inoculum of 5 . 10(3) L. monocytogenes resulted either in prolonged survival compared with normal mice of the recipient haplotype or in definitive survival accompanied by a positive delayed-type sensitivity. We concluded that enhanced nonspecific immune functions can in part compensate for the defective specific immune system after bone marrow transfer.     

Invariant V alpha 14+ NKT cells participate in the early response to enteric Listeria monocytogenes infection

Invariant Valpha14(+) NKT cells are a specialized CD1-reactive T cell subset implicated in innate and adaptive immunity. We assessed whether Valpha14(+) NKT cells participated in the immune response against enteric Listeria monocytogenes infection in vivo. Using CD1d tetramers loaded with the synthetic lipid alpha-galactosylceramide (CD1d/alphaGC), we found that splenic and hepatic Valpha14(+) NKT cells in C57BL/6 mice were early producers of IFN-gamma (but not IL-4) after L. monocytogenes infection. Adoptive transfer of Valpha14(+) NKT cells derived from TCRalpha degrees Valpha14-Jalpha18 transgenic (TCRalpha degrees Valpha14Tg) mice into alymphoid Rag(null) gamma(c)(null) mice demonstrated that Valpha14(+) NKT cells were capable of providing early protection against enteric L. monocytogenes infection with systemic production of IFN-gamma and reduction of the bacterial burden in the liver and spleen. Rechallenge experiments demonstrated that previously immunized wild-type and Jalpha18null mice, but not TCRalpha(null) or TCRalpha(null) Valpha14Tg mice, were able to mount adaptive responses to L. monocytogenes. These data demonstrate that Valpha14(+) NKT cells are able to participate in the early response against enteric L. monocytogenes through amplification of IFN-gamma production, but are not essential for, nor capable of, mediating memory responses required to sterilize the host.