Cytotoxic Activity Of Spleen Cells Research Articles

Combined therapy with methotrexate nanoconjugate and dendritic cells with downregulated IL-10R expression modulates the tumor microenvironment and enhances the systemic anti-tumor immune response in MC38 murine colon carcinoma.

Understanding the negative impact of the tumor microenvironment on the creation of an effective immune response has contributed to the development of new therapeutic anti-cancer strategies. One such solution is combined therapy consisting of chemotherapeutic administration followed by dendritic cell (DC)-based vaccines. The use of cytostatic leads to the elimination of cancer cells, but can also modulate the tumor milieu. Moreover, great efforts are being made to increase the therapeutic outcome of immunotherapy, e.g. by enhancing the ability of DCs to generate an efficient immune response, even in the presence of immunosuppressive cytokines such as IL-10. The study aimed to determine the effectiveness of combined therapy with chemotherapeutic with immunomodulatory potential - HES-MTX nanoconjugate (composed of methotrexate (MTX) and hydroxyethyl starch (HES)) and DCs with downregulated expression of IL-10 receptor stimulated with tumor antigens (DC/shIL-10R/TAg) applied in MC38 murine colon carcinoma model. With the use of lentiviral vectors the DCs with decreased expression of IL-10R were obtained and characterized. During in vivo studies MC38-tumor bearing mice received MTX or HES-MTX nanoconjugate as a sole treatment or combined with DC-based immunotherapy containing unmodified DCs or DCs transduced with shRNA against IL-10R (or control shRNA sequence). Tumor volume was monitored during the experiment. One week after the last injection of DC-based vaccines, tumor nodules and spleens were dissected for ex vivo analysis. The changes in the local and systemic anti-tumor immune response were estimated with the use of flow cytometry and ELISA methods. In vitro studies showed that the downregulation of IL-10R expression in DCs enhances their ability to activate the specific anti-tumor immune response. The use of HES-MTX nanoconjugate and DC/shIL-10R/TAg in the therapy of MC38-tumor bearing mice resulted in the greatest tumor growth inhibition. At the local anti-tumor immune response level a decrease in the infiltration of cells with suppressor activity and an increase in the influx of effector cells into MC38 tumor tissue was observed. These changes were crucial to enhance the effective specific immune response at the systemic level, which was revealed in the greatest cytotoxic activity of spleen cells against MC38 cells.

Effects of Activation of Maternal Immune System at Early Stages of Pregnancy on Antitumor Immunity of the Progeny

The effects of maternal immune system on the formation and functioning of the fetus is an important problem. Single stimulation of immune system of female C57Bl/6 mice with concanavalin A at the early stages of pregnancy before the formation of fetal immune organs was followed by impairment of antitumor immunity in the progeny by the time of puberty. These changes manifested in the increased survival rate of B16 melanoma, high rate of death of tumor-bearing animals, and low cytotoxic activity of spleen cells on L-929 fibrosarcoma cells.

Antitumor effect of murine dendritic and tumor cells transduced with IL-2 gene

Interleukin (IL-) 2 acts on a number of types of immune cells promoting their effector functions. To replace systemic administration of recombinant form of this cytokine, various genetically modified cells have been used indifferent preclinical models for tumor growth inhibition. In this study, dendritic or tumor cells transduced with retroviral vector carrying IL-2 gene (JAWS II/IL-2, X63/IL-2, MC38/IL-2 cells) alone or combined with tumor antigen-stimulated dendritic cells (JAWS II/TAg) were exploited to treat colon carcinoma MC38-bearing mice. After the peritumoral injection of vaccine cells, the tumor growth delay and the increase in the number of tumor infiltrating CD4⁺ and CD8⁺ T lymphocytes were noted. A considerable increase in CD4⁺ cell influx into tumor tissue was observed when JAWS II/IL-2 cells or JAWS II/TAg with syngeneic MC38/IL-2 cells were applied. The increase in intensity of CD8⁺ cell infiltration was associated with immune reaction triggered by the same combination of applied cells or JAWS II/TAg with allogeneic X63/IL-2 cells. The effect observed in vivo was accompanied by MC38/0 cell specific cytotoxic activity of spleen cells in vitro. Thus, the application of vaccines, including IL-2-secreting cells of various origins, was able to induce different antitumor responses polarized by exogenous IL-2 and the encountered tumor antigen.

Generation of protective immune responses against coxsackievirus B3 challenge by DNA prime–protein boost vaccination

Coxsackievirus B3 (CVB3) causes viral myocarditis and can ultimately result in dilated cardiomyopathy. However, there is no vaccine available for clinical use. In this study, we assessed the protection provided by three immunization strategies against CVB3 infection. Vaccination was performed with a DNA vaccine expressing the cloned capsid gene VP1 or a vaccine developed from purified VP1 protein. Third, a strategy of vaccination was attempted with the DNA vaccine followed by two boosts with the recombinant protein vaccine (DNA prime–protein boost vaccine). Followed immunization, mice were challenged with CVB3 infection. Improved induction of CVB3-specific antibodies and neutralizing antibodies were found in mice immunized by the DNA prime–protein boost regimen. Furthermore, virus-specific cytotoxic activity of spleen cells derived from DNA prime–protein boost vaccinated mice was elicited. In addition, the DNA prime–protein boost vaccine resulted in protection of 75% of mice from lethal CVB3 challenge and a significant reduction of viral load in sera of immunized mice after acute CVB3 infection. There was a significant reduction in myonecrosis and infiltrating myocardial immune cells indicating reduced severity of myocarditis in surviving mice. These findings demonstrated that a DNA prime–protein boost immunization strategy, but not a DNA vaccine or protein vaccine alone, was effective in eliciting both humoral and cell-mediated immune responses against CVB3 infection in mice and might be a promising vaccine candidate.

Antitumoral efficacy by systemic delivery of heparin conjugated polyethylenimine-plasmid interleukin-15 complexes in murine models of lung metastasis

Gene therapy shows promising application in cancer therapy, but the lack of an ideal gene delivery system is still a tough challenge for cancer gene therapy. Previously, we prepared a novel cationic nanogel, heparin-polyethylenimine (HPEI), which had potential application in gene delivery. In the present study, we constructed a plasmid with high expression efficiency of interleukin-15 (IL15) and investigated the effects HPEI-plasmid IL15 (HPEI-pIL15) complexes on the distribution level of the lung. We then evaluated the anticancer effect of HPEI-pIL15 complexes on lung metastases of B16-F10 melanoma and CT26 colon carcinoma. These results demonstrated that intravenous injection of the HPEI-pIL15 complex exhibited the highest plasmid distribution level in the lung compared with that of PEI2K-pIL15 and PEI25K-pIL15, and mice treated with HPEI-pIL15 had a lower tumor metastasis index compared with other treatment groups. Moreover, the number of natural killer cells, which were intermingled among the tumor cells, and the level of tumor necrosis factor-α and interferon-γ in the serum also increased in the pIL15-treated mice. Furthermore, the cytotoxic activity of spleen cells also increased significantly in the HPEI-pIL15 group. In addition, induction of apoptosis and inhibition of cell proliferation in lung tumor foci in the HPEI-pIL15 group was observed. Taken together, treating lung metastasis cancer with the HPEI nanogels delivered by plasmid IL15 might be a new and interesting cancer gene therapy protocol.

Preclinical efficacy data of MGN1601, a tumor vaccine comprising 4-fold gene-modified and irradiated allogeneic tumor cells in combination with a DNA-based immunomodulator for the treatment of metastatic renal carcinoma.

e15067 Background: MGN1601 is a cell-based tumor vaccine for the treatment of mRCC. MGN1601 consists of two active pharmaceutical ingredients. One consists of allogeneic, human tumor cells, derived from RCC tissue, and transfected in-vitro with four different MIDGE vectors for transient expression of human IL-7, GM-CSF, CD80 and CD154. The other ingredient is the DNA-based immunomodulator dSLIM-30L1, mainly a TLR-9 agonist. Methods: Murine tumor models were used to evaluate the efficacy of a murine homologue of MGN1601 (mMGN1601). mMGN1601 was set up from Renca cells and transfected with 4 different MIDGE vectors for transient expression of mouse IL-7, GM-CSF, CD80 and CD154. For tumor inoculation in syngenic BALB/c mice Renca cells were used. For efficacy of the vaccine in a prophylactic setting, mice were vaccinated with mMGN1601 and thereafter challenged with Renca cells. In therapeutic settings Balb/c mice first received naïve Renca cells and were subsequently vaccinated four times with different test items, either the complete mMGN1601 or one out of three lacking different components. To address the mode of action, modulations of the immune system were monitored in NMRI mice (allogeneic setting). Results: Prophylactic setting: None of the vaccinated mice showed tumor growth, whereas all of the tumor-bearing mice of the control group died due to the tumor growth. Efficacy evaluation in the therapeutic setting revealed, that the complete tumor vaccine clearly achieved the most pronounced effects in tumor reduction, showing a survival of 92%, compared to 25% survival in the control group. The incomplete derivatives led to less pronounced therapeutic efficacy. The immunomodulatory effects of mMGN1601 in allogeneic NMRI mice generated a more than 3-fold increase of the cytotoxic activity of spleen cells, an augmented T-cell proliferation (> 6-fold) and an increase of CD4+, CD8+ and CD86+ cells at the site of vaccination (up to 20-fold). Conclusions: The murine homologue of MGN1601 showed excellent antitumor efficacy and significant pharmacological effects in murine models. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration MOLOGEN AG MOLOGEN AG MOLOGEN AG

Soybean protein fraction digested with neutral protease preparation, “Peptidase R”, produced by Rhizopus oryzae, stimulates innate cellular immune system in mouse

A soybean protein fraction was prepared from defatted soybean seed flour and digested with 29 kinds of commercially available protease originating from preparations of animals, plants, and microorganisms. Some digests, in particular, Ro-digest prepared using a Rhizopus oryzae neutral protease preparation (Peptidase R), displayed strong mitogenic activity toward C3H/HeN mouse spleen cells. The number of spleen CD11b +, CD49b +, interleukin (IL)-12 +CD11b +, and interferon (IFN)-γ +CD49b + cells significantly increased when cultured with Ro-digest. Similarly, the number of spleen IFN-γ +CD4 + cells significantly increased in the presence of Ro-digest while that of spleen IL-4 +CD4 + cells was largely unchanged. Additionally, 5-week-old male C3H/HeN mice were given diets consisting of ovalbumin (OVA) alone (control diet) or a mixture of OVA and Ro-digest (Ro-digest-added diet) as a protein source for 5 weeks, and the immune properties of the mice were investigated. The number of IL-12 +CD11b + cells was greater in spleens from mice given the Ro-digest-added diet than in those given the control diet. The cytotoxic activity of spleen cells toward the human erythroleukemia cell line, K562, was significantly higher in mice given the Ro-digest-added diet than in those given the control diet. Furthermore, in a microarray analysis of mRNAs extracted from mice Peyer's patch cells, gene expression related to innate immune responses was increased in mice given the Ro-digest-added diet. These results indicate that the Ro-digest might stimulate cellular immune systems, in particular, an innate immunity in mice.

Characterization of a Cellular Immunostimulating Peptide from a Soybean Protein Fraction Digested with Peptidase R

An immunostimulating glutamine-rich peptide was purified from a soybean protein fraction digested with Peptidase R produced by Rhizopus oryzae (Ro-digest) by a combination of SP-Sepharose column chromatography and reversed-phase high-performance liquid chromatography. The purified peptide was supposed to be located at or near the glutamine-rich region 202 to 222 of the glycinin G4 subunit. The peptide significantly increased the number of CD8(+), CD11b(+), and CD49b(+) cells in C3H/HeN mouse spleen cell cultures, while 2 chemically synthesized glutamine-rich peptides corresponding to residues 202 to 213 (QQQQQQKSHGGR) and residues 214 to 225 (KQGQHQQEEEEE) of the glycinin G4 subunit increased the number of interleukin (IL)-12(+)CD11b(+) cells. The peptide 202-213 also significantly increased the number of CD49b(+), IL-2(+)CD4(+), and interferon-gamma(+)CD4(+) cells and stimulated the cytotoxic activity of spleen cells toward the human erythroleukemia cell line K562. These results indicate that the glutamine-rich region of the soybean glycinin G4 subunit stimulates the cellular immune system in mouse spleen cell cultures.

Successful cancer vaccine therapy for carcinoembryonic antigen (CEA)‐expressing colon cancer using genetically modified dendritic cells that express CEA and T helper‐type 1 cytokines in CEA transgenic mice

This study was designed to determine whether the vaccination of genetically modified dendritic cells (DCs) simultaneously expressing carcinoembryonic antigen (CEA), granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin 12 (IL-12) can overcome the peripheral T-cell tolerance to CEA and thereby elicit a therapeutic response in CEA transgenic mice. CEA transgenic mice were immunized once by subcutaneous injection with DCs adenovirally transduced with CEA and T helper-type 1 cytokine genes. The cytotoxic activity of spleen cells against CEA-expressing tumors, MC38-CEA, in the mice immunized with DCs expressing CEA (DC-AxCACEA) was higher than that in those immunized with DCs-AxCALacZ (p < 0.0001), and was augmented by the cotransduction with the GM-CSF/IL-12 gene (p < 0.05). The vaccination with DC-AxCACEA/GM-CSF/IL-12 could elicit a more potent therapeutic immunity than the vaccination with DC-AxCACEA in subcutaneous tumor models (p < 0.0001), and 4 of 5 mice showed a complete eradication of the subcutaneous tumors in these vaccination groups. Even in a large tumor model, this vaccination therapy completely eliminated the subcutaneous tumors in all mice. This antitumor activity mostly vanished with the depletion of CD8(+) T cells and NK cells in vivo and was completely abrogated with the depletion of CD4(+) T cells. A histopathological examination showed no evidence of an autoimmune reaction. No other adverse effects were observed. This vaccination strategy resulted in the generation of highly efficient therapeutic immune responses against MC38-CEA in the absence of autoimmune responses and demonstrated no adverse effects, and may therefore be useful for future clinical applications as a cancer vaccine therapy.

Oral ingestion of cow's milk immunoglobulin G stimulates some cellular immune systems and suppresses humoral immune responses in mouse

Four-week-old male C3H/HeN mice were bred with diets consisting of ovalbumin alone (OVA, control diet) or mixtures of OVA and cow's milk immunoglobulin G (IgG-added diets) as a protein source for 4 or 5 weeks, and both the cellular and humoral immune properties of the mice were investigated. The number of interleukin (IL)-12 +CD11b + cells in spleens and the formation of superoxide by peritoneal macrophages were higher in mice given the IgG-added diet than in those given the control diet. The number of natural killer cells in Peyer's patches or spleens and the cytotoxic activity of spleen cells toward an erythroleukemia cell line, K562, were also higher in mice given the IgG-added diet. In contrast, the numbers of interferon-γ +CD4 + and IL-4 +CD4 + cells in Peyer's patches or spleens and the levels of total or OVA-specific intestinal IgA and serum IgG were significantly lower in mice given the IgG-added diet than in those given the control diet. In addition, the number of cells expressing CD19 in spleens was significantly higher in mice given the IgG-added diet. These results indicate that oral ingestion of cow's milk IgG may stimulate some innate cellular immune systems, while suppressing humoral adaptive immune responses in the mouse.

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 interleukin-2 gene-modified fibroblasts in an orthotopic colon cancer model.

We transduced the interleukin‐2 (IL‐2) gene into murine fibroblasts BALBCL7 or murine colon cancer CT26 using a retroviral vector. BALBCL7 transduced with IL‐2 gene secreted 748 pg/ml of IL‐2, whereas IL‐2 gene‐modified CT26 secreted 1,167 pg/ml of IL‐2 (48 h incubation, 1×106/ml). Then, we inoculated gene‐modified BALBCL7 and/or CT26 cells into BALB/c female mice, and observed the tumor growth. The tumor growth was inhibited in mice inoculated with parental CT26 plus IL‐2 gene‐modified BALBCL7, compared with that in mice given parental CT26 alone (P < 0.01). Moreover, we investigated the cytotoxic activity of spleen cells derived from mice treated with gene‐modified cells, and performed phenotypic analysis of the effector cells. The killer cells derived from mice inoculated with IL‐2 gene‐modified BALBCL7 plus parental CT26 showed higher cytotoxic activity than those from mice inoculated with CT26 alone. The cytotoxic activity was almost completely blocked by anti‐CD8 antibody (Ab), and partially blocked by anti‐asialo GM1 Ab. Next, we inoculated CT26 tumor tissue into murine cecum orthotopically, and treated the animals with gene‐modified BALBCL7 plus parental CT26. The tumor size in the cecum was significantly decreased, compared with parental CT26 alone (P < 0.01).

Genetic immunotherapy by intrapleural, intraperitoneal and subcutaneous injection of IL-2 gene-modified Lewis lung carcinoma cells.

The induction and augmentation of tumor non-specific immunity and of tumor-specific immunity by intrapleural, intraperitoneal and subcutaneous injection of interleukin-2 (IL-2) gene-modified Lewis lung carcinoma (LLC) cells (LLC-IL2) was tested in C57BL/6 mice. Intrapleural injection of LLC cells induced lung tumors with a malignant effusion, intraperitoneal injection induced peritoneal tumors with ascites and subcutaneous injection induced subcutaneous tumors. Intrapleural injection of irradiated LLC-IL2 cured pre-existing lung LLC tumors and extended the survival of the mice but did not affect survival of mice with pre-existing peritoneal tumors nor did it affect the growth of s.c. tumors. Intraperitoneal injection of irradiated LLC-IL2 cured pre-existing LLC peritoneal tumors and extended the survival of the mice but did not affect survival of mice bearing lung tumors nor did it affect the growth of s.c. tumors. Subcutaneous injection of irradiated LLC-IL2 did not affect the growth of preexisting s.c. tumors and also did not improve survival of mice bearing the lung or peritoneal tumors. Injection with irradiated LLC-IL2 by all routes, i.e., intrapleural, intraperitoneal and s.c., protected against subsequent re-challenge with LLC. Eight days after the initial immunization (early stage of immunization), non-adherent mononuclear cells in the peritoneal cavity of the mice treated with intraperitoneal injection of irradiated LLC-IL2 displayed enhanced cytotoxicity against LLC, B16-F10 and P815 cells, while the cytotoxic activity of spleen cells in the same mice did not change. The efficiency of induction of tumor-specific immunity was the strongest after intraperitoneal immunization and weakest after s.c. immunization. In vitro analysis using the spleen cells of mice immunized with irradiated LLC-IL2 suggested that CD8+ T cells play a key role in tumor-specific immunity.

The cytotoxic T lymphocyte response in reticuloendotheliosis virus-infected chickens is mediated by αβand not by γδ T cells

We induced a virus-specific cytotoxic T lymphocyte (CTL) response in B2 chickens by i.v. inoculation with 100 TCID 50 of the reticuloendotheliosis virus (REV). Chickens were sacrificed 7 days after the infection and cytotoxic activity of the spleen cells against various target cells was assayed in a 4 h 51Cr-release assay at an effector to target ratio of 100:1. In addition, T cell receptor (TCR) αβand TCR γδ cells were negatively selected from the REV-immune spleen cells and used as effector cells against REV-infected B2 target cells. (On average 40 % of spleen T cells express TCR γδ in the chicken.) By inhibition of the cytotoxic activity of the immune spleen cells against REV-infected syngeneic target cells with monoclonal antibodies specific for chicken CD3 and CD8 molecules, the effector cells could be identified as CD8 + T cells. The cytotoxic activity was MHC-restricted, as only syngeneic but not allogeneic REV-infected target cells were lysed by REV-immune spleen cells, and virus-specific, as no cytotoxic activity could be found using uninfected syngeneic target cells. When assaying the activity of the negatively selected, > 98 % pure αβ and γδ T cells, it was found that αβ T cells exerted virus-specific CTL activity ranging from 26 to 62 % specific 51Cr-release, while γβ T cells showed only 2–4 % 51Cr-release. These data indicate that REV-specific CTL response is mediated by αβ T cells and that γδ T cells are not involved in virus-specific CTL activity in the spleen of REV-infected chickens.

B30-MDP, a synthetic muramyl dipeptide derivative for tumour vaccination to enhance antitumour immunity and antimetastatic effect in mice

The effect of a muramyl dipeptide derivative (B30-MDP) on the augmentation of antitumour immunity against highly metastatic L5178Y-ML25 mouse lymphoma cells was examined in CDF1 (Balb/c × DBA/2) mice. Mice immunized with a mixture of X-irradiated tumour cells (103) and B30-MDP (100 μg) on 7 days prior to challenge by viable tumour cells displayed a significant decrease in metastasis towards the target organs, liver and spleen, compared with that of untreated mice. Immunization of mice with the mixture on day 5 or 7 after tumour challenge, when the level of glutamic-pyruvic transaminase (GPT) and glutamic-oxaloacetic transaminase (GOT) in sera of mice inoculated with viable tumour cells was observed to be normal, caused less metastasis than immunization with X-irradiated tumour cells alone. Sensitization with X-irradiated tumour cells admixed with B30-MDP induced almost two times higher cytotoxicity of spleen cells against L5178Y-ML25 lymphoma cells than sensitization with X-irradiated tumour cells without B30-MDP. In contrast, cytotoxic activity of spleen cells against another target, L1210 lymphoma cells derived from BDF1 mice, was not observed by immunization with X-irradiated L5178Y-ML25 cells with or without B30-MDP. Specific lysis by splenic cells of the immunized mice against L5178Y-ML25 cells decreased to the normal level when T cells were deleted from the immunized spleen cells by the treatment of rabbit anti-mouse Thy1.2 antibody and rabbit complement. These results indicate that B30-MDP is able to augment a specific tumour immunity due to the enhancement of cytotoxicity mediated by T lymphocytes, and is useful as an immunopotentiating agent for active immunization of inactivated tumour cells.

Effect of LTB4 on the inhibition of natural cytotoxic activity by PGE2

NK activity is regulated by arachidonic acid metabolites. More precisely PGE2 and LTB4 decreases and increases respectively non-MHC-restricted cytotoxicity in humans. We have observed similar data in mice since NK activity was inhibited by PGE2 (10 −6 to 10 −8 M) and enhanced by LTB4 (10 −8 to 10 −12 M). On the other hand when PGE2 and LTB4 were combined during the same assay the lysis percentage was smaller than the one which was induced by PGE2 alone. Because PGE2 increases intracellular cyclic AMP and that LTB4 augments cyclic GMP we used a cAMP inducer (forskolin) and a cGMP analogue (8 Br-cGMP) instead of eicosanoids and we observed similar data (i.e., a decrease of natural killing) as when PGE2 was combined with LTB4. When splenocytes are cultured for 1–4 days alone, cytotoxic activity decreases unless they are cultured in the presence of indomethacin. Cytotoxic activity of spleen cells cultured in the presence of PGE2 or LTB4 is respectively decreased or increased. However, splenocytes that were cultured alone for at least 24 hr were no longer sensitive to inhibition by PGE2 but were still PGE2-sensitive when cultured in the presence of LTB4.

Effect of Toxoplasma lysate antigen (TLA) on feline cytotoxicity against FeLV positive lymphoma cells.

The cytotoxic activities of feline spleen cells treated with Toxoplasma lysate antigen (TLA) were assayed against feline leukemia virus (FeLV)-producing lymphoma. FL74 cells, and xenogeneic target lymphoma, mouse YAC-1 cells. The TLA treatments were performed in vivo alone, in vitro alone, and in vivo plus in vitro, respectively. In vivo plus in vitro treatments with TLA induced a marked augmentation in cytotoxic activity of spleen cells to FL74 cells. The treatment with TLA in vivo alone showed an enhancement of cytotoxic activity but in vitro alone did not. The cytotoxic effects of TLA-treated spleen cells obtained from the cats which had been previously immunized with live FL74 cells were similar to those of spleen cells from non-immunized cats treated with TLA. However, no increase of cytotoxicity was shown in the response to mouse YAC-1 cells regardless of TLA treatments. These results indicated that the in vivo TLA treatment augmented the cytotoxicity of feline spleen cells against FeLV-producing lymphoma cell.

Decrease of transplantability by the immunopotentiators, OK-432 and interleukin-2: Experiments on a human hepatoma cell line in nude mice

The relationship between nonspecific cytotoxic activity of spleen cells and the resistance against the graft challenge of a human hepatoma cell line (HCC-M) was investigated in nude mice. Two administrations of an immunopotentiator, OK- 432 or human interleukin- 2, prior to the subcutaneous inoculation of HCC-M cells, which was performed 24 h after the last administration, significantly inhibited the tumor development in terms of rate of tumor take and tumor size. This effect was abrogated by simultaneous administration of an anti-asialo GM 1 (ASGM 1) antiserum. There was a significant inverse correlation between tumor volume and spleen cell cytotoxicity which was determined at the time of HCC-M cell inoculation against a YAC- 1 or HCC-M target. Spleen cell cytotoxicity enhanced by these immunopotentiators could not completely be abolished by in vitro treatment with ASGM 1 and complement. This result suggests that effector cells of the enhanced cytotoxicity consist of heterogeneous cells including both ASGM 1+ natural killer cells and other nonselective cytotoxic cells. These results suggest that nonspecific cytotoxic cells play crucial roles in the resistance against tumor cell challenge and that the total level of cytotoxic activity of these cells at the time of tumor cell challenge is a key factor which determines tumor development.

Effect of diuciphon on natural cytotoxic activity of spleen cells of old mice

Effect of diuciphon on natural cytotoxic activity of spleen cells of old mice