A materially-closed aquatic-ecosystem: a useful tool for determining changes of ecological processes in space

A materially-closed aquatic ecosystem (microcosm) was developed. The microcosm contained two families of green algae and blue-green alga as primary producers, protozoa, two species of rotifers and oligochaetes as consumers, and bacteria as decomposers. The microcosm could be readily replicated. It was confirmed the population densities of each organism were almost constant for 365 days without artificial operation except temperature and light. The population dynamics and the spatial patterns of the organisms were simulated by mathematical models. This hermetically-sealed microcosm could be a useful subject to investigate ecology under space environment.

Transgenic Japanese lawngrass (Zoysia japonica Steud.) plants regenerated from protoplasts

Transgenic Japanese lawngrass (Zoysia japonica Steud.) plants were generated by means of polyethylene glycol (PEG)-mediated direct gene transfer into protoplasts. The plasmid pBC1 was used to deliver the hygromycin phosphotransferase (hph) and β-glucuronidase (gus) genes into protoplasts. Selection with a high concentration (400 mg/l) of hygromycin yielded a number of resistant calli and about 400 plants were generated. Polymerase chain reaction (PCR) and Southern hybridization analyses revealed that all of then plants tested contained introduced genes. The gus gene regulated by the maize alcohol dehydrogenase-1 (Adh 1) promoter was expressed in the leaves and roots of transgenic Japanese lawngrass plants.

Effects of administration of monoclonal antibodies (anti-CD4 or anti-CD8) on the development of autoimmune diseases in (NZW x BXSB)F1 mice

(NZW x BXSB)F1 (W/BF1) mice spontaneously develop autoimmune diseases, characterized by lymphadenopathy, lupus nephritis, and immune thrombocytopenia associated with various autoantibodies such as anti-DNA, anti-platelet and anti-cardiolipin antibodies (Abs). In the present study, we investigate the effects of administration of monoclonal Abs (anti-CD4 or anti-CD8 mAb) on the development of autoimmune diseases in W/BF1 mice. MAb was administered from the age of 7 weeks. Prolongation of survival rate and reduction of severity of autoimmune diseases were observed after treatment with anti-CD4 mAb. However, anti-CD8 mAb treatment accelerated the diseases. Serum levels of IFN-gamma and IL-10 in old W/BF1 mice were significantly high, whereas IL-4 levels were low in comparison with those of young W/BF1 mice; the expression of mRNA of IFN-gamma, IL-4 or IL-10 in CD4+ T cells of old W/BF1 mice was parallel to the serum levels of each cytokine. These observations suggest that CD4+ cells are involved in the development of autoimmune diseases in W/BF1 mice, and that CD8+ cells have a suppressive effect on the development of autoimmune diseases in W/BF1 mice.

Preventive effects of various ginseng saponins on the development of copulatory disorder induced by prolonged individual housing in male mice

Recently, we found that virtually all male mice failed to display copulatory behavior following prolonged individual housing. The present study was conducted to investigate whether or not ginseng saponin components prevent the development of this copulatory disorder. ICR male mice were housed individually for 5 weeks after weaning, followed by a 10-min encounter with an estrous female mouse. The following constituents of red ginseng powder were administered intraperitoneally once per day throughout the individual housing period: crude ginseng saponins and pure ginsenoside Rb1, Rb2, Rg1, and Ro. Three elements of copulatory behavior (mounting, intromission and penis licking) were determined. Following prolonged individual housing only one mouse in the vehicle-treated group displayed mounting. Chronic treatment with crude ginseng saponins (25, 50 and 100 mg/kg) significantly lessened the severity of copulatory disorder in a dose-dependent manner. Ginsenoside Rg1 (2.5, 5 and 10 mg/kg) also resulted in a significantly higher incidence of copulatory behavior as compared to the individually housed vehicle-treated group, whereas ginsenoside Rb1, Rb2 and Ro were ineffective. This evidence indicates that ginsenoside Rg1 is one of the ingredients of red ginseng root that acts on male copulatory behavior.

Intrathymically injected hemopoietic stem cells can differentiate into all lineage cells in the thymus: differences between c-kit+ cells and c-kit < low cells

To investigate whether hemopoietic stem cells (HSCs) can differentiate into all lineage cells even in the thymus, we injected two types of HSCs (c-kit+ and c-kit < low cells) obtained from C57BL/6 Ly5.1 mice directly into the thymus of 7.5 Gy-irradiated C57BL/6 Ly5.2 mice. When c-kit < low cells (low density/lineage-/CD71-/major histocompatibility complex class I high/Sca-1+/Thy-1low/ c-kit < low) were injected, donor-derived (Ly5.1) cells were detected on day 8 after intrathymic (i.t.) injection, and the number reached a maximum on day 24 after injection. Granulocytes and macrophages were also detected on day 8 after injection. However, B220+ B cells were observed on day 13. Eighteen days after i.t. injection, the injected lobes showed red color due to the synchronous development of erythroid cells. Histological studies revealed the development not only of erythroid lineage cells but also of megakaryocytes in the thymus. In contrast, when c-kit+ cells were injected, a significant number of donor-derived cells were detected on day 5 after i.t. injection (three days earlier than in the case of c-kit < low cell injection). The differentiation into erythroid lineage cells was also observed six days earlier than when c-kit < low HSCs were injected. These findings suggest that c-kit < low HSCs are more primitive than c-kit+ HSCs, although both can differentiate into all lineage cells after i.t. injection.

Requirement of major histocompatibility complex-compatible microenvironment for spleen colony formation (CFU-S on day 12 but not on day 8)

To clarify major histocompatibility complex (MHC) restriction between hematopoietic stem cells (HSCs) and microenvironments, T cell-depleted bone marrow cells (BMCs) were transplanted into MHC-compatible and MHC-incompatible recipients. A significantly larger number of spleen colony-forming units (CFU-S) on day 12 were noted in MHC-compatible recipients, while only a small number were observed in MHC-incompatible recipients. There was, however, no significant difference in CFU-S counts on day 8 between the two groups. A large number of CFU-S counts on day 12 were also observed in F1 hybrid recipients, as seen in syngeneic recipients. The decrease in CFU-S counts on day 12 in MHC-incompatible recipients was also observed even after in vivo abrogation of T and NK cells. The difference in CFU-S counts on day 12 became more prominent when HSC-enriched cells were transferred. These results suggest that an MHC restriction exists between pluripotent HSCs (P-HSCs) and spleen microenvironments. Furthermore, experiments using B10. A recombinant strains revealed that H-2D and S loci play a crucial role in the MHC restriction. The experiments of serial transplantation suggest that the differentiation and proliferation of P-HSCs are inhibited in MHC-incompatible microenvironments. It is therefore likely that the MHC-compatible microenvironment is essential to the differentiation and proliferation of P-HSCs.

Induction of donor-specific T cell anergy by portal venous injection of allogeneic cells

The mechanisms behind tolerance induction by portal venous (pv) injection of allogeneic cells are investigated. When a hematopoietic stem cell (HSC)-enriched population of BALB/c bone marrow was pv injected into C57BL/6 mice, the response of the T cells in the B6 mice to BALB/c alloantigens in mixed lymphocyte reaction (MLR) decreased until day 4 after the injection. Neither clonal deletion of V beta 11+ T cell nor donor-specific suppressor activity was observed. When recipient T cells were separated into CD4+ and CD8+ cells, only the CD8+ cell population showed donor-specific tolerance. The donor cells were trapped and retained in the host liver. MHC class I antigens were highly expressed on the trapped cells whereas class II antigens or B7 costimulatory molecules were not. The tolerance to BALB/c alloantigens in MLR was obtained also by the pv injection of Meth A, a BALB/c-derived sarcoma cell line. However, tolerance was not induced by the pv injection of B7-transfected Meth A cells. In addition to MLR, tolerance was also observed in DTH responses, and this was also due to the unresponsiveness of CD8+ cells to the donor alloantigens. However, the BALB/c-specific DTH responses were not suppressed after the pv injection of B7-transfected Meth A cells. These results strongly suggest that the tolerance induced by pv injection of allogeneic cells is due to clonal anergy generated by the absence of costimulatory signals in the interaction between donor-specific CD8+ T cells and donor hematopoietic cells trapped in the host liver.

Cord blood IgE against milk and egg antigens

The aim of the present study was to reevaluate the prenatal production of specific IgE for eggs and milk and, in those cases, to determine whether there is a relation to the amount of maternal egg and milk intake. Total and specific IgEs from 160 cord blood-samples were determined by immunoassays using a paramagnetic particle solid phase and an enzyme-mediated chemiluminescent reaction for signal detection. The levels of cord blood IgE for total, egg, and milk were 0.63 +/- (SD) 1.10 IU/ml, 0.020 +/- 0.055, and 0.036 +/- 0.053 IU/ml, respectively. IgE levels specific to egg and milk over 0.03 IU/ml were observed in 33 and 70 out of 160 cases, respectively. To address whether the maternal intake of eggs and milk affects the level of cord blood IgEs, all mothers except 9 were interviewed, and the amount of eggs and milk taken during pregnancy was recorded. No correlation was seen between egg and milk intakes and cord blood IgE levels. Our data demonstrate a high incidence of the prenatal production of specific IgE for eggs and milk which is independent of maternal egg and milk intakes.

Low frequency of autoantibodies against Ki-67 antigen in Japanese patients with systemic autoimmune diseases

The Ki-67 antigen, which is recognized by the monoclonal antibody Ki-67, is a marker of cell proliferation. During cDNA cloning using sera from a patient with systemic lupus erythematosus, we obtained a positive clone encoding part of Ki-67. We determined the frequency of autoantibodies against Ki-67 in patients with systemic autoimmune diseases. Serum samples from 252 patients with rheumatic diseases were examined by immunoblotting with HeLa nuclear extract and the recombinant N-terminus of the Ki-67 antigen. Autoantibodies against Ki-67 antigen were detected in two out of 76 patients with systemic lupus erythematosus and one out of 90 patients with scleroderma. While, in a previous report, anti-Ki-67 antibodies were frequently targeted by a certain strain of autoimmune mice, our results indicated that Ki-67 was a minor target of autoantibodies among Japanese patients with systemic autoimmune diseases.

An animal model of copulatory disorder induced by social stress in male mice: effects of apomorphine and L-dopa

We investigated the possible role of dopamine receptors in the mediation of copulatory disorder induced by defeat experience in male mice, using L-dopa and apomorphine. To generate the copulatory disorder, male mice were attacked 20 times daily for 5 consecutive days, as intruders in confrontation with an aggressive resident. Following the repeated exposure to defeat, virtually all intruder males failed to display copulatory behavior towards estrous females. Acute injection of apomorphine (25, 50, 75 micrograms/kg, s.c.) significantly increased both the incidence and the frequency of copulatory elements (mounting and intromission) in a dose-dependent manner. The combination of L-dopa with carbidopa, a dopa decarboxylase inhibitor, also increased significantly copulatory behavior, revealing an inverted U-shaped dose-effect curve. In both cases, locomotion and digging frequencies were significantly decreased. This evidence suggests that dopaminergic mechanisms are involved in the mediation of social stress-induced copulatory disorder.

Expression cloning and intracellular localization of a human ZF5 homologue

We isolated a cDNA encoding a human homologue of ZF5 (hZF5), which has five Kruppel-like C2H2 type zinc fingers at carboxyl terminus and the BTB/POZ (poxvirus and zinc finger) at the amino terminus, using autoimmune sera from a patient with overlap syndrome (dermatomyositis and scleroderma). Sequencing of the entire cDNA revealed an open reading frame (ORF) of 1349 bp with a deduced protein sequence of 449 amino acid residues and a calculated molecular weight of 51.3 kDa. The deduced amino acid sequence of hZF5 is highly homologous to mouse ZF5 (99.3% identity). Immunofluorescence studies revealed that HA-tagged hZF5 transiently expressed in COS-7 cells showed the nuclear dot pattern in the BTB/POZ domain-dependent manner.

Major histocompatibility complex restriction between hematopoietic stem cells and stromal cells in vivo

Graft failure is a mortal complication in allogeneic bone marrow transplantation (BMT); T cells and natural killer cells are responsible for graft rejection. However, we have recently demonstrated that the recruitment of donor-derived stromal cells prevents graft failure in allogeneic BMT. This finding prompted us to examine whether a major histocompatibility complex (MHC) restriction exists between hematopoietic stem cells (HSCs) and stromal cells. We transplanted bone marrow cells (BMCs) and bones obtained from various mouse strains and analyzed the cells that accumulated in the engrafted bones. Statistically significant cell accumulation was found in the engrafted bone, which had the same H-2 phenotype as that of the BMCs, whereas only few cells were detected in the engrafted bones of the third-party H-2 phenotypes during the 4 to 6 weeks after BMT. Moreover, the BMCs obtained from the MHC-compatible bone showed significant numbers of both colony-forming units in culture (CFU-C) and spleen colony-forming units (CFU-S). These findings strongly suggest that an MHC restriction exists between HSCs and stromal cells.

Mini ecosystem in space--preliminary experiment on board STS-77

An enclosed ecosystem which is stable on Earth will behave differently when brought into space. Micro-gravity and radiation will affect the dynamics of material circulation or the activities of small creatures of the ecosystem. One series of space experiments aiming to address such issues was planned in the United States (It is termed as ABS--Autonomous Biological System) and Japanese group has been involved with cooperating with the analysis of the flight samples. Before the ecosystem will be on board Russian Space Station "Mir" later 1996 for 3 months, a preliminary flight was carried out in May 1996 on Space Shuttle (STS-77) for 10 days flight. It was the first of such experiments to fly one whole ecosystem in space.

Hyponatremia with consciousness disturbance caused by omeprazole administration. A case report and literature review

A 68-year-old man developed severe consciousness disturbance after daily administration of 20 mg omeprazole for four days for the treatment of bleeding gastric ulcer. Systemic investigation revealed severe hyponatremia (111 meq/liter). Consciousness did not become clear until his sodium intake was increased to 480 meq/day, and his serum sodium concentrations reached 130 meq/liter. After the discontinuation of omeprazole, his serum sodium levels returned to the normal range with only minimum supplementation of sodium in the form of dietary sodium chloride intake of 10 g/day. Although the mechanism of hyponatremia induced by omeprazole is not clear, an excessive loss of urinary sodium appears to be more likely than water retention with an increase in fluid intake. The literature was also reviewed.

Plant regeneration from protoplasts of Japanese lawngrass

Embryogenic callus of Japanese lawngrass (Zoysia japonica Steud.) was induced from sterile mature seeds on LS medium with 5 mg / l of 2,4-D. Embryogenic callus selected visually under microscope was proliferated in liquid N6 medium with amino acids (N6-AA medium). Protoplasts were isolated from suspension cells by the treatment of enzyme mixture containing pectolyase Y-23 and cultured in K8p medium with 2 mg / l of 2,4-D at the density of 10(6) / ml. Plants were regenerated by transferring the protoplasts derived callus to MS medium and incubating at 28 °C under light for two months. Plantlets were successfully transplanted in the soil.

Interleukin-12 induces cytotoxic NK1+ alpha beta T cells in the lungs of euthymic and athymic mice

We recently reported that interleukin-12 (IL-12) stimulated hepatic NK1.1 Ag+ alpha beta T cells with intermediate T-cell receptor (TCR; NK1+ TCRint cells) and enhanced their NK1 expression (NK1high TCRint), and that these cells acquire strong major histocompatibility complex (MHC) unrestricted cytotoxicity in C57BL/6 mice, both +/+ and nu/nu. In the present study, we find that although murine lung normally has few NK1+ TCRint cells, NK1high TCRint cells are induced in+/+ and nu/nu mice after systemic administration of IL-12; these cells exhibit strong MHC unrestricted cytotoxicity against NK-sensitive and -resistant targets. A small number of NK1high TCRint cells was also found in peripheral blood after increased amounts of IL-12 were administered. Cytotoxicity tests in vitro revealed that the cytotoxic activity of the lung mononuclear cells (MNC) of C57BL/6 mice induced by IL-12 was abrogated by the depletion of either NK1+ or CD3+ cells, but not of CD8+ cells, as reportedly was the case of hepatic MNC, suggesting that NK1high TCRint cells are an antimetastatic population not only in the liver but also in the lung of mice. IL-12 injection into mice markedly elevates serum interferon-gamma (IFN-gamma) levels. However, although IL-12-induced cytotoxicity of NK1high TCRint cells was significantly reduced by anti-IFN-gamma antibody injection (which decreased serum IFN-gamma to an undetectable level), the appearance of NK1high TCRint cells in the lung and liver was not so affected. These results suggest that IFN-gamma is an important mediator of the cytotoxicity of NK1high TCRint cells but is not an essential factor for induction of these cells. We also added data showing that IL-12 has a broad antimetastatic effect against various liver and lung metastatic tumours intravenously injected into several strains of mice, including NK-deficient bg/bg mice. It can be considered that, in addition to NK cells, CD8+ cytotoxic T cells and gamma delta T cells, NK1+ TCRint cells can be categorized as one of the cytotoxic effector populations. These novel type cells distinct from regular T cells may play an important role in monitoring intra- and perivascular areas.

Liver NK1.1+ CD4+ alpha beta T cells activated by IL-12 as a major effector in inhibition of experimental tumor metastasis

We demonstrate herein evidence that IL-12-activated alpha beta T cells with intermediate TCR (NK1+ TCRint cells) in the liver inhibit metastases in the lung as well as in the liver metastases of i-v. injected tumors. IL-12 administration enhanced NK1 expression of NK1+ TCRint cells (NK1high) and increased CD4 weakly positive (CD4low) TCRint cells, while both CD4+ TCRint cells and double-negative TCRint cells were proportionally diminished. Accordingly, the major parts of NK1high TCRint cells are CD4low cells, and most of these cells are V beta 8+ cells. The cytotoxic assays of IL-12-stimulated hepatic mononuclear cells after treatment with respective Abs and complement in vitro and after sorting revealed that CD4low NK1high TCRint cells are cytotoxic effectors. When IL-12-stimulated hepatic mononuclear cells (but not splenocytes) were transferred into tumor-preinjected mice, EL-4 cell metastases in the liver as well as 3LL cell metastases in the lung were inhibited. The antimetastasis of hepatic mononuclear cells transfer was abrogated by the depletion of NK1+ cells, CD3+ cells, or CD4+ cells but not CD8+ cells before transfer. Moreover, transfer of these cells of nude mice into tumor-preinjected mice also inhibited metastases in both organs. Although NK1+ TCRint cells are nearly absent in the hepatic vein blood, a significant proportion of NK1high TCRint cells appeared by IL-12 administration. These results demonstrate that IL-12-stimulated liver NK1high TCRint cells, including extrathymic ones, are major effectors against tumor metastasis and suggest that the cells migrate and inhibit lung metastases.

Liver NK1.1+ CD4+ alpha beta T cells activated by IL-12 as a major effector in inhibition of experimental tumor metastasis

We demonstrate herein evidence that IL-12-activated alpha beta T cells with intermediate TCR (NK1+ TCRint cells) in the liver inhibit metastases in the lung as well as in the liver metastases of i-v. injected tumors. IL-12 administration enhanced NK1 expression of NK1+ TCRint cells (NK1high) and increased CD4 weakly positive (CD4low) TCRint cells, while both CD4+ TCRint cells and double-negative TCRint cells were proportionally diminished. Accordingly, the major parts of NK1high TCRint cells are CD4low cells, and most of these cells are V beta 8+ cells. The cytotoxic assays of IL-12-stimulated hepatic mononuclear cells after treatment with respective Abs and complement in vitro and after sorting revealed that CD4low NK1high TCRint cells are cytotoxic effectors. When IL-12-stimulated hepatic mononuclear cells (but not splenocytes) were transferred into tumor-preinjected mice, EL-4 cell metastases in the liver as well as 3LL cell metastases in the lung were inhibited. The antimetastasis of hepatic mononuclear cells transfer was abrogated by the depletion of NK1+ cells, CD3+ cells, or CD4+ cells but not CD8+ cells before transfer. Moreover, transfer of these cells of nude mice into tumor-preinjected mice also inhibited metastases in both organs. Although NK1+ TCRint cells are nearly absent in the hepatic vein blood, a significant proportion of NK1high TCRint cells appeared by IL-12 administration. These results demonstrate that IL-12-stimulated liver NK1high TCRint cells, including extrathymic ones, are major effectors against tumor metastasis and suggest that the cells migrate and inhibit lung metastases.

Isolation and partial structure of a unique lipophilic peptide, VAP peptide, from the heads of male silkworm moths

A new lipophilic peptide was isolated from the MeOH-CH2Cl2 extract of adult heads of the male silkworm, Bombyx mori, by monitoring the diapause egg-inducing activity. Partial amino acid sequencing (1-55) revealed this peptide to be a unique type having a high content of lipophilic amino acids, Val, Ala, and Pro, and many repeating sequences. The compound was thus named VAP peptide.

Distribution of neuronal cytoplasmic inclusions in multiple system atrophy

Neuronal cytoplasmic inclusions (NCIs) were demonstrated by means of silver staining (Gallyas staining) in the central nervous systems of 18 deceased patients with multiple system atrophy (MSA) - 6 with olivopontocerebellar atrophy (OPCA), 6 with striatonigral degeneration (SND) and 6 with Shy-Drager syndrome (SDS). We observed NCIs in the cerebral cortex, putamen, pons, medulla oblongata and spinal cord, and especially in the putamen and pons of all cases with MSA. No NCIs were observed in the cerebellum and midbrain. The findings were common to all 3 subtypes of MSA. NCIs were not present in patients with other neurodegenerative disorders and non-neurological disorders. Our findings indicate that NCIs represent a special neuronal alteration characteristic of MSA and support the theory that OPCA, SND and SDS represent manifestations of a single condition i.e. MSA.

Rapidly growing histologically benign meningiomas: cell kinetic and deoxyribonucleic acid ploidy features: report of three cases

We present three cases of histologically benign meningiomas with a rapid and known time course to the development of symptoms. Tumor doubling time calculated from sequential computed tomographic scans and computer-assisted image analysis of proliferating cell nuclear antigen reactivity suggested rapid growth. Feulgen staining indicated deoxyribonucleic acid aneuploidy. Tests for progesterone and estrogen receptor immunoreactivity were negative. These cases are noteworthy for their uncharacteristically rapid growth in the absence of histological evidence of atypia.

Abnormalities of B cells and dendritic cells in SAMP1 mice

The age-related changes in the function of antigen-presenting cells (APC) were examined using a substrain of senescence-accelerated mouse (SAMP1). In the primary mixed lymphocyte reaction (MLR), dendritic cells (DC) from aged SAMP1 mice showed less stimulatory activity than those of age-matched BALB/c or young SAMP1 mice. In the secondary MLR, the stimulatory activity of B cells was found to be lower in aged SAMP1 mice but not in age-matched BALB/c or young SAMP1 mice. In addition, these age-related decreases in the stimulatory activity of APC were found to be related to changes in the surface density of major histocompatibility complex class II and intercellular adhesion molecule-1 (ICAM-1) (but not B7-1 or B7-2 molecule) on APC (DC and B cells).

Cytotoxic NK1.1 Ag+ alpha beta T cells with intermediate TCR induced in the liver of mice by IL-12

Systemic administration of IL-12 greatly reduced the hepatic metastases of i.v.-injected liver metastatic EL4 tumor cells in C57BL/6 +/+ and nu/nu mice. Cytotoxic assay in vitro revealed that administration of IL-12 greatly enhanced cytotoxicity of hepatic mononuclear cells (MNC) against various NK- sensitive and -resistant tumor targets, including EL4 cells, whereas only slight or moderate augmentation of the cytotoxicity was observed in splenocytes in normal and nude mice. After IL-12 administration, hepatic MNC increased in number and showed vigorous proliferation in vitro. Hepatic MNC of control C57BL/6 +/+ mice contain alpha beta T cells with intermediate TCR (TCRint) as well as alpha beta T cells with bright TCR, whereas hepatic MNC of nu/nu mice have only TCRint cells. These TCRint cells are found to be NK1.1 Ag+ (NK1+ TCRint). Systemic administration of IL-12 into normal and nude mice markedly augments the NK1 expression of NK1+ TCRint cells (NK1high TCRint), which is comparable to or brighter than that of NK cells in the liver, whereas alpha beta T cells with bright TCR or gamma delta T cells in the liver are NK1-. Depletion of either NK1.1+ or CD3+ cells, but not CD8+ cells, of hepatic MNC from IL-12-treated normal mice by respective Abs and C in vitro abrogate their cytotoxicity. These results revealed that TCRint cells are potent cytotoxic effector cells and suggest that NK1high TCRint cells are the main antimetastatic population in the liver, and that TCRint cells are functionally different from regular T cells with bright TCR.

Cytotoxic NK1.1 Ag+ alpha beta T cells with intermediate TCR induced in the liver of mice by IL-12

Systemic administration of IL-12 greatly reduced the hepatic metastases of i.v.-injected liver metastatic EL4 tumor cells in C57BL/6 +/+ and nu/nu mice. Cytotoxic assay in vitro revealed that administration of IL-12 greatly enhanced cytotoxicity of hepatic mononuclear cells (MNC) against various NK- sensitive and -resistant tumor targets, including EL4 cells, whereas only slight or moderate augmentation of the cytotoxicity was observed in splenocytes in normal and nude mice. After IL-12 administration, hepatic MNC increased in number and showed vigorous proliferation in vitro. Hepatic MNC of control C57BL/6 +/+ mice contain alpha beta T cells with intermediate TCR (TCRint) as well as alpha beta T cells with bright TCR, whereas hepatic MNC of nu/nu mice have only TCRint cells. These TCRint cells are found to be NK1.1 Ag+ (NK1+ TCRint). Systemic administration of IL-12 into normal and nude mice markedly augments the NK1 expression of NK1+ TCRint cells (NK1high TCRint), which is comparable to or brighter than that of NK cells in the liver, whereas alpha beta T cells with bright TCR or gamma delta T cells in the liver are NK1-. Depletion of either NK1.1+ or CD3+ cells, but not CD8+ cells, of hepatic MNC from IL-12-treated normal mice by respective Abs and C in vitro abrogate their cytotoxicity. These results revealed that TCRint cells are potent cytotoxic effector cells and suggest that NK1high TCRint cells are the main antimetastatic population in the liver, and that TCRint cells are functionally different from regular T cells with bright TCR.