An analysis of conditions allowing Corynebacterium parvum to cause either augmentation or inhibition of natural killer cell activity against tumor cells in mice

CD137-Deficient Mice Have Reduced NK/NKT Cell Numbers and Function, Are Resistant to Lipopolysaccharide-Induced Shock Syndromes, and Have Lower IL-4 Responses

CD137, a member of the TNF superfamily, is involved in T cell and NK cell activation and cytokine production. To establish its in vivo role in systems dependent on NK and NKT cells, we studied the response of CD137-/- mice to LPS-induced shock, tumor killing, and their IL-4-controlled Th2 responses. In both high and low dose shock models, all the CD137-deficient mice, but none of the wild-type BALB/c mice, survived. After injection of LPS/2-amino-2-deoxy-D-galactose (D-gal), CD137-/- mice had reduced serum cytokine levels and substantially impaired liver IFN-gamma and TNF-alpha mRNA levels. Phenotypic analysis of mononuclear cells revealed fewer NK and NKT cells in the CD137-/- mice. The knockout mice did not generate a rapid IL-4 response after systemic T cell activation, or effective Ag-specific Th2 responses. In addition, both in vitro and in vivo NK-specific cytolytic activities were reduced. These findings suggest that CD137-directed NK/NKT cells play an important role in the inflammatory response leading to the production of proinflammatory cytokines, LPS-induced septic shock, and tumor killing, as well as IL-4-dependent Th2 responses.

Heterogeneity in the ability of cytotoxic murine NK cell clones to enhance Ig secretion in vitro

We recently described a panel of cytotoxic murine NK cell clones that also enhanced Ig secretion by B cells activated in an in vitro model of T cell-independent type 2 (TI-2) responses. We employed dextran-conjugated anti-IgD (alphadelta-dex) as a model antigen. Here we study the mechanism of Ig induction by these clones. Addition of the various NK clones to sort-purified B cells stimulated with alphadelta-dex and IL-2 resulted in a markedly heterogeneous increase in Ig secretion, which varied from 3-fold, as mediated by clone PKO 56, to 15-fold, as induced by clone PKO 101. The other NK cells showed intermediate levels of Ig induction. Furthermore, while addition of as few as 0.04% of PKO 101 cells stimulated significant increases and 1% induced near maximum Ig production, a 3% addition of PKO 56 cells was required for significant enhancement of Ig secretion. Supernatant material collected from the NK clones mediated Ig production at levels that mirrored the induction by the corresponding cells. Cytokine analysis showed that while all members of the NK panel produced IFN-gamma only two secreted granulocyte macrophage colony stimulating factor and that the levels of Ig induction mediated by the NK clones correlated only with their levels of IFN-gamma secretion. Culture of B and NK cells in the presence of anti-IFN-gamma demonstrated that IFN-gamma was the critical cytokine in NK-induced Ig production. These findings establish heterogeneity in the ability of NK cells to increase Ig secretion in vitro and show that NK-produced IFN-gamma is an important factor in determining this heterogeneity.

Natural killer cells are a source of interferon gamma that drives differentiation of CD4+ T cell subsets and induces early resistance to Leishmania major in mice

Infection of mice with the protozoan Leishmania major provides an excellent model to define the factors involved in T helper (Th) subset development, since Th1 cells confer protection in resistant strains of mice, whereas Th2 cells are associated with the fatal outcome of susceptible mice. We previously found that interferon gamma (IFN-gamma) was required for Th1 cell development after infection of mice with L. major. In this report, we evaluate the contribution of natural killer (NK) cells to IFN-gamma levels early in L. major infection. NK cell activity was higher in resistant C3H/HeN mice than in susceptible BALB/c mice during the first week of infection, and removal of NK cells significantly decreased IFN-gamma levels and promoted interleukin 4 (IL-4) production in both the draining lymph nodes and spleen. IFN-gamma production by NK cells required the presence of CD4+ T cells or IL-2, but not CD8+ T cells. Enhanced disease, as measured by parasite numbers and lesion development, was observed in NK cell-depleted mice. Furthermore, a comparison of the NK cell response and the subsequent parasite burden in several inbred strains of mice demonstrated that NK cells mediate early resistance to L. major. Together, these data indicate that the stimulation of NK cells, through the production of IFN-gamma, plays an important role in initiating Th1 cell differentiation in leishmaniasis and in controlling early resistance to L. major.

Alteration in natural defense activity against NK-susceptible B16 melanoma cells after treatment with Corynebacterium parvum

We have investigated the effects of administration of C. parvum on host anti-metastatic activity against B16 melanoma H-2L, a natural killer (NK) sensitive clone with a low expression of H-2b. The anti-metastatic activity was estimated by monitoring the following two points. One was the survival ratio at an early stage after an intravenous (iv) inoculation of radiolabeled B16 H-2L cells, the other was the formation of pulmonary metastases after iv injection with the tumor cells. Administration of C. parvum showed a biphasic change in the NK activity of the spleen cells and the peritoneal exudate cells (PEC) in mice. At an early phase (2-3 days) after administration of C. parvum, the NK activity of the spleen cells and PEC was significantly augmented. On the other hand, at a later phase (14 days) after C. parvum administration, the NK activity was deeply depressed. In correlation with NK activity of the mice treated with C. parvum, the anti-metastatic activity of the hosts was augmented in the early phase, whereas a depressed level of anti-metastatic activity was observed in the late phase after administration of C. parvum. These results suggest that the modification of NK activity is a possible basis for modulation of anti-metastatic activity by C. parvum.

Antitumor activity of Streptococcus thermophilus against fibrosarcoma: role of T-cells

Antitumor activity induced by a heat-killed preparation of S. thermophilus against mouse fibrosarcoma was investigated. The treatment of Swiss mice with S. thermophilus prior to transplantation could not prevent tumors. However, animals cured by treatment with a S. thermophilus preparation failed to take up the tumor when rechallenged with fibrosarcoma. S. thermophilus did not induce antitumor activity in animals immunosuppressed by sublethal whole body gamma-irradiation (4 Gy) or hydrocortisone treatment prior to transplantation. Suppression of activity of macrophages by carrageenan had no effect on antitumor activity of the heat inactivated preparation of S. thermophilus. The intravenous administration of sera from cured animals was ineffective in curing the tumours. Spleen cells from cured animals could effectively transfer the antitumor activity to recipients transplanted with the tumor. This effect was abolished when the T-lymphocyte population in the inoculum was specifically depleted. The results thus suggest the involvement of T-lymphocytes in antitumor activity exhibited by S. thermophilus.

Characterization of Corynebacterium parvum-induced suppressor cells of mouse NK and ADCC activity

Treatment of mice with Corynebacterium parvum (Cp) resulted in a substantial decrease in natural killer activity in the spleen at 10 days. The decrease in cytotoxicity was associated with the presence of splenic nonadherent (NA) suppressor cells, capable of inhibiting natural as well as antibody-dependent cellular cytotoxicity (ADCC). The nonadherent suppressor cells appeared to be null cells, lacking detectable expression of Thy 1, L3T4 (CD4), Lyt 2 (CD8), or asialo-GM1 and could be physically separated from cells with NK activity by centrifugation on Percoll discontinuous density gradients. Our results indicate that Cp can negatively modulate cytolytic functions of NK cells by inhibiting the effector phase of cytotoxicity.

Host environment as a modulating factor of swine natural killer cell activity

The large granular lymphocyte (LGL) population includes such heterologous effector cells as the natural killer (NK), lymphokine activated killer (LAK), antibody dependent cellular cytotoxic (ADCC) and non-MHC restricted T cells. These LGL subpopulations have all been associated with NK activity. In some species, enhanced NK activity is correlated with exposure to viral, bacterial and parasitic agents. Consequently, the host environment could serve as a modulatory factor of NK activity in laboratory animals. During our investigation of tumor regression in melanoma swine, we observed marked differences in the NK activity of peripheral blood lymphocytes collected from two separate groups of Sinclair melanoma miniature swine maintained under different conditions. Group A pigs were vaccinated and extensively treated for endo- and ectoparasites while group B swine were not. In addition, chronic exposure to infectious and parasitic diseases have been documented in the group B swine. Peripheral blood NK activity was assessed by standard in vitro 4-h chromium release assays. The NK activity of group B swine was markedly exaggerated when compared to group A swine. Thus, the significance of NK activity may be distorted as a result of the modulating effect of pathogen exposure.

The immunosuppressive activities of two abortifacient proteins isolated from the seeds of bitter melon (Momordica charantia)

Two abortifacient proteins, alpha- and beta-momorcharin, have been purified from the seeds of the bitter melon (Momordica charantia). It was found that non-cytotoxic concentrations of these plant proteins can significantly inhibit the mitogenic responses of mouse splenocytes to concanavalin A, phytohaemagglutinin and lipopolysaccharide in a dose-dependent manner. In addition, the alloantigen-induced lymphoproliferation and the in vitro generation of a primary cytotoxic lymphocyte response were severely suppressed in the presence of these proteins. In contrast, the cytolytic activity of cytotoxic lymphocytes and natural killer cells was unimpaired by in vitro exposure to momorcharin. On the other hand, a clear decrease in the functional capacity of macrophages, such as the cytostatic and phagocytic activities, was observed under similar conditions. In vivo studies have shown that single injections of nontoxic microgram amounts of momorcharin into mice resulted in a significant depression of the delayed-type hypersensitivity response as well as the humoral antibody formation to sheep red blood cells. Similarly, the thioglycollate-induced in vivo migration of macrophages was also suppressed. Interestingly, the in vivo activation of natural killer cells was not appreciably affected. Our data suggests that the observed potent immunosuppressive effect of alpha- and beta-momorcharin is unlikely to be due to direct lymphocytotoxicity or due to a shift in the kinetic parameter of the immune response.

The cytolytic and regulatory role of natural killer cells in experimental neoplasia

NK cells are defined here as cells, other than macrophages and polymorphonuclear leucocytes, from non-immunized animals (or humans) which are cytotoxic for neoplastic and non-neoplastic targets in the absence of specific antibody. Though not requiring antibody, they may function as K cells in ADCC. This definition includes cells activated nonspecifically by such agents as IFN and IL-2. Murine NK cells may be subdivided into two types by differences in the kinetics of target-cell lysis. Those we label Type 1 correspond roughly to what others have called NKA, NKL or simply NK cells; those of Type 2 to NKB, NKS and NC cells. Type 1 cells express various antigens, including NK-1, Thy-1 (50%), Ly-1 (25%), Qa-3, Qa-4, Qa-5, Ly-5, Ly-6, Ly-10, Ly-11 and asialo-GM1, not expressed by Type 2 cells, whereas Mac-1 may be expressed by both types. At least some NK cells appear to be pre-thymic cells which, in the presence of a thymus, can differentiate into T cells. The level of NK activity is influenced by the age and genetic background of the mouse, the organ from which the cells are obtained, and a variety of experimental manipulations. Type 1 activity is increased by IFN and IL-2; Type 2 activity by IL-3. IFN appears to be concerned in the development of spontaneous NK activity in young mice. Many experiments have shown that NK cells may inhibit the growth of tumours which are sensitive to NK cells of the same type in vitro. Inhibitory cells which suppress NK activity may play an important regulatory role in vivo. There is still uncertainty about how NK cells recognize their targets. Possibilities discussed are: (1) specific interacting molecules; (2) more diffuse properties of target cell membranes; (3) absence of MHC-coded self-recognition markers. Certainly, the presence of a Class 1 MHC molecule is not necessary. NK killing appears to be mediated by cytotoxins released by NK cells. In vivo, NK cells contribute to limiting the development of transplanted and primary tumours, and metastasis from established tumours. NK cells seem well qualified to act as a first-line defence against neoplasia, and may kill cells not killed by T cells. Transfer of NK cells may be of value in the treatment of cancer.

Augmentation of NK activity and/or macrophage-mediated cytotoxicity in the liver by biological response modifiers including human recombinant interleukin 2

Administration of several biological response modifiers (BRMs) to mice strongly augmented natural killer (NK) activity of leukocytes isolated from the liver. This augmentation of NK activity was induced by two synthetic molecules (MVE-2 and poly ICLC), by two BRMs of bacterial origin (formalin-fixed Propionibacterium acnes: P. acnes and a streptococcal cell wall preparation designated OK-432), as well as a single injection of human recombinant interleukin-2 (hrIL 2). All of these BRMs augmented NK activity in the liver to a greater degree than in the spleen. In addition, adherent leukocytes (greater than 90% macrophages) isolated from the liver following P. acnes administration also exhibited augmented macrophage-mediated cytotoxicity. This cytotoxicity was characterized as macrophage mediated and distinguished from NK activity, on the basis of adherence purification, kinetics of cytotoxicity, and target cell selectivity. The results demonstrate that a variety of BRMs induce augmented natural immunity in the liver and suggest that such organ-associated immune responses may play an important role in the antimetastatic effects of BRMs.

Inhibition of mouse natural killer cytotoxicity by heparin

The effect of heparin on mouse natural killer (NK) cytotoxicity was investigated. Heparin greatly inhibited NK activity at a concentration of more than 10 units/ml. Inhibition of NK cytotoxicity was observed only when heparin was present in the reaction mixture of the cytotoxicity assay. The results of kinetic study of NK inhibition and target-effector binding assay proposed the possibility that heparin inhibits NK cytotoxicity after the binding of effector cells to target cells. Dextran sulfate, the heparin analog, which has potent negative charge also had an inhibitory effect on NK activity. Fractionation of heparin on Sephadex A-25 column revealed the parallelism of the negative charge and the inhibitory effect of heparin on NK cytotoxicity. These results demonstrated that polyanion could modulate NK cytotoxicity.

Induction of natural killer cell activity by inactivated Candida albicans in mice

Injection of merthiolate-inactivated yeast form cells of Candida albicans into the peritoneal cavities of mice induced the appearance of a cytolytic effector population against YAC-1 tumor cell lines. This induction was maximally manifested in 5- to 8-week-old animals 3 to 4 days after injection of 2 X 10(7)C. albicans cells, and the peritoneal lytic population exerted its optimum cytotoxic effect after 4 h of incubation. No significant natural cytotoxic activity was generated by C. albicans in the bone marrow or thymus, whereas there was a slight, transient, but significant depression of natural splenic cytotoxicity. Experiments performed to characterize the natural cytotoxic population elicited by the inactivated yeast showed that the effectors were nonadherent, nonphagocytic cells. Moreover, the anti-YAC-1 lytic activity was partially sensitive to anti-Thy1.2 serum and was completely abrogated by treatment of peritoneal nonadherent cells with monoclonal anti-asialo GM1 antibodies. Finally, the peritoneal population of cytotoxic cells induced by C. albicans was fully susceptible to Ly5.1 plus anti-immunoglobulin G2a and complement lysis. Although different cell populations could be induced by inactivated C. albicans, all of our data support the view that the anti-YAC-1 activity was entirely attributable to natural killer lymphocytes.

Intraperitoneal administration of interferon beta in ovarian cancer patients

Eight patients with advanced ovarian carcinomas resistant to conventional chemotherapy were injected with interferon (IFN) beta (3 X 10(6) U) intraperitoneally twice a week. Seven subjects had ascites. Side effects included abdominal pain, fever, and constipation, but no hematologic toxicity was observed. Growth of solid tumor lesions was unaffected by IFN beta, with the possible exception of one patient who had stable disease. IFN beta intraperitoneally inhibited completely the formation of ascites in four of seven patients with effusions. Natural killer (NK) cell activity was measured in peripheral blood and tumor-associated lymphocytes (PBL and TAL). Using stringent criteria that included repeated assessment of baseline activity, a clear cut increase in NK cytotoxicity of TAL was detected in two of six subjects from whom TAL could be purified. Augmentation of NK activity was restricted to the peritoneal compartment with no effect on PBL. Studies on biologic response modifiers encompassing an analysis of events taking place at sites directly involved by neoplasia may provide an opportunity for generating information on the in situ regulation of tumor-associated host defense mechanisms in humans.

Interferon inducibility in mice treated with Corynebacterium parvum

Mice were given single intraperitoneal (i.p.) injections of Corynebacterium parvum, followed, after different time intervals, by i.p. injections of the interferon inducers polyinosinic-polycytidylic acid (poly-I:poly-C), 10-carboxymethyl-9-acridanone (CMA) or herpes simplex virus. With all three inducers production of interferon in the peritoneal cavity was enhanced in C. parvum-pretreated mice. Production of circulating interferon in C. parvum-pretreated mice was enhanced with CMA and depressed with poly-I:poly-C as inducers. This modulation of the interferon response was prominent for at least 10 weeks after C. parvum injection and then gradually reverted. The increased local interferon production seemed to be caused by macrophages still activated several weeks after treatment with C. parvum.

The effect of treatment with Corynebacterium parvum on the development and growth of experimental hematogenic metastases of schwannoma in the rat

Single i.v. administration of Corynebacterium parvum 5 days before i.v. injection of 10(6) tissue cultured syngeneic schwannoma cells in Lewis rats resulted in extension of survival time (P less than 0.05). There was a significant decrease in metastatic tumor incidence for lung, heart, and kidney and decreased lung tumor growth with approximately 50% of the lung tumor burden of untreated controls (P less than 0.05). Rats treated similarly with C. parvum 10 days after tumor cell injection showed no enhanced survival; to the contrary, their survival was shortened. Moreover, tumor incidence in the post-treated group was not significantly different from the control but significantly increased in comparison to the pretreated group. Enhanced lung tumor growth resulted in a final tumor burden about twice that of untreated controls (P less than 0.05).

Stimulatory effect of Propionibacterium granulosum KP-45, glucan and pyran copolymer on the activity of natural killer (NK) cells in murine lungs

Propionibacterium granulosum KP-45, glucan and pyran copolymer stimulated the elimination of 75Selenomethionine-labelled 3LL tumor cells from murine lungs, as measured 4 hr after intravenous injection of these cells into 16- to 25-week-old B6DF1 mice. This effect was most pronounced 4 to 6 days following intravenous administration of the above biological response modifiers and disappeared 6 to 8 days later. Intraperitoneal injection of all three agents produced only insignificant stimulation results. Spontaneous clearance of 3LL cells from lungs of 8-week-old B6DF1 mice was significantly more effective than in animals over 16 weeks old. Cyclophosphamide suppressed the elimination of tumor cells from lungs in both young and older mice and neutralized the stimulatory effect of P. granulosum KP-45 and glucan. The results suggest that the effector cells responsible for the clearance of radiolabelled 3LL cells from lungs of B6DF1 mice are at least similar to natural killer (NK) lymphocytes.

Leukemia induction by methylnitrosourea (MNU) in selected mouse strains. Effects of MNU on hemopoietic stem cells, the immune system and natural killer cells

T cell leukemias were induced by a single dose of methylnitrosourea (MNU) in DBA/2, C57/Bl/6, NMRI, BDF1, and CBA mice. The latency period in the CBA strain was much longer than in the others. Studies on the pluripotent stem cells in the bone marrow and T cell reactions of thymus and spleen cells showed a toxicity of MNU for these parameters but no significant differences between the strains. The activity of the natural killer (NK) cells in the spleen and peritoneal exudate cells, studied also after additional stimulation by injection of Corynebacterium parvum, was influenced by MNU, but again no relation to leukemogenesis could be established. The first leukemic (transplantable) cells were found in the thymus. The presence of leukemic cells could be responsible for low NK cell activities found in BDF1 and DBA/2 mice late after MNU.

Modulation of natural killer activity in mice following infection with Listeria monocytogenes

Mice that received a sublethal, intraperitoneal dose of viable Listeria monocytogenes, virulent strain 10403, exhibited a systemic increase in natural killer (NK) activity. The kinetics of the response differed with respect to the various effector cell populations analyzed. Resident peritoneal cells and peripheral blood leukocytes demonstrated high NK activity on Days 3, 7, and 10. Peak spleen and bone marrow NK activity was observed on Day 3, returning to normal levels by Day 7. In contrast, peritoneal exudate cells, elicited with proteose peptone, expressed enhanced NK activity for 60 days following infection with viable Listeria. Augmented NK activity was detected with all cell types as early as 12 hr after infection. The intraperitoneal injection of nonviable antigenic preparations derived from L. monocytogenes, strain 10403, resulted in the enhancement of peritoneal and splenic NK activity. In contrast, mice that received an intraperitoneal injection of avirulent Listeria, strain 19113, failed to express enhanced levels of NK activity. The genetic trait of anti-listerial resistance which is associated with non-H-2 linked genes was of no importance with respect to enhanced NK activity. Listeria-resistant C57BL/6J and Listeria-susceptible DBA/2J mice both produced systemic augmentation of NK activity following infection. NK activity was not abrogated by macrophage depletion or by treatment with anti-Thy 1.2 serum plus complement. These results confirm the potent immunostimulatory capacity of virulent Listeria for NK activity and provide further insight into the kinetics of this response in various lymphoid compartments. The protracted augmentation of NK activity of elicited peritoneal exudate cells as compared to nonelicited peritoneal cells in Listeria-primed mice suggests that the influx of inflammatory cells may provide NK-enriched and/or accessory populations for immunopotentiation of NK activity in inflammatory sites.

Augmentation of mouse natural killer cell activity by Lactobacillus casei and its surface antigens

Lactobacillus casei YIT 9018 (LC 9018) augmented the natural killer (NK) cell activity of spleen cells from inbred BALB/c mice injected intravenously with LC 9018 or intraperitoneally with polyinosinate -polycytidylate. Augmentation of this activity by LC 9018 was also observed in male C3H/He, CBA/N, and C57BL/6 mice. The spleen cells exhibited no cytolytic activity against P815, a cell line insensitive to NK cells. The cytolytic activity of the spleen cells increased 2 days after the injection of 250 micrograms of LC 9018/mouse, peaked on day 3, and gradually declined thereafter. The increase caused by LC 9018 was also observed in normal and Meth A-bearing mice. In vitro treatment with anti-asialo GM1 antibody plus complement completely abrogated the LC 9018-augmented murine NK cell activity. The NK activity on the 3rd day after LC 9018 injection was reduced by in vitro treatment with anti-Thy 1.2 monoclonal antibody plus complement to half of that observed when treatment was with complement alone. This suggests that there were two populations of NK cells in the spleen cell suspension derived from LC 9018-treated mice. One population was asialo GM1-positive and Thy 1-negative, the other was asialo GM1-positive and Thy 1-positive.

Studies on natural killer cell activity and the influence of Corynebacterium parvum on murine T-cell leukemogenesis induced by butylnitrosourea

Butylnitrosourea (BNU) was used to induce thymic lymphomas in BDF1 mice. During and after the 12-week BNU exposure the spontaneous NK cell activity against YAC-1 cells and that arising 4 days after stimulation with Corynebacterium parvum (CP) were measured, as were the mitogen responses of splenic T and B cells. In addition to BNU, groups of mice received multiple injections of the interferon inducer CP during or after the BNU exposure period. The results show a slight impairment of the NK cell activity by BNU and also after the injections of CP depending heavily on the treatment protocol. After the multiple injections of CP, either into BNU-treated mice or into controls, no further stimulation by CP was possible. The mitogen responses, reduced after BNU, were further reduced after the additional treatment. Both effects can be explained by the known induction of suppressor cells by CP. Although these treatments had pronounced effects on the parameters tested in vitro there was no significant influence on the development of thymic lymphomas in vivo.

The seeding of a transplanted murine leukemia and its influence on hemopoietic stem cells and immune function of the host

A butylnitrosourea-induced murine T-cell leukemia, L40, was transplanted in BDF1 mice; 1 X 10(3) cells killed all recipients after conditioning with 400 rad, whereas 1 X 10(5) were needed with normal recipients. No leukemic cells could be detected by transplantation or cytogenetic analysis in the femur or the spleen at day 6 after L40 inoculation and, at day 11, leukemic cells were found in one out of two experiments, more if the host had been irradiated. Up to day 17, when leukemic cells were present, the CFU-S and CFU-C content of the femur was normal, but later a loss was observed with an increase in the enlarging spleen. Lymphocyte-stimulation assays with spleen cells gave normal results up to day 17, but later the 3H-thymidine uptake of stimulated T and B cells was reduced. The NK-cell activity with and without stimulation by Corynebacterium parvum in the spleen began to fall at day 17 and was absent later; this loss was also observed with peritoneal exudate cells. In vitro mixing experiments of L40 cells with normal spleen cells showed "cold target inhibition" by L40 cells in the NK-cell assay as well as interference with the lymphocyte stimulation.

Enhancement of natural killer cell activity and 2-5A synthetase in mice treated with polyadenylic.polyuridylic acid

Previous studies have demonstrated that splenic natural killer (NK) cell activity of mice can be efficiently enhanced by polyadenylic.polyuridylic acid [poly(A).poly(U)]. Moreover, inoculation of mice with the duplex leads to the production of interferon (IFN). The NK boosting effect in mice was analyzed in parallel with the assay of an enzyme marker for the production and action of IFN, pppA(2'p5'A)n synthetase (2-5A synthetase). Kinetic studies revealed that splenic mononuclear cells of C3H/He mice inoculated intravenously with 10 micrograms or more of poly(A).poly(U) showed significantly enhanced cytotoxic activity in an in vitro 51Cr-release assay using NK sensitive YAC-1 target cells. Intravenous, intraperitoneal, and intramuscular administration of the duplex into mice were equally effective in obtaining such NK boosting effect. Furthermore, repeated weekly injections of poly(A).poly(U) did not induce resistance against NK boosting in the organisms. The levels of 2-5A synthetase in the organs, particularly spleens, of mice inoculated similarly with poly(A).poly(U) were greatly increased with a dose-dependent pattern. Repeated injections of mice with the duplex at 4-day intervals resulted also in significantly enhanced levels of splenic 2-5A synthetase after each injection. Thus, as a whole, enhanced NK activity accompanied increased levels of 2-5A synthetase in mice treated with poly(A).poly(U).

Mode of protection of mice against herpes simplex virus type 2 infection by Propionibacterium

We compared various strains of Propionibacterium with regard to protection of young adult mice against lethal infection with herpes simplex virus type 2 (HSV-2). Propionibacterium acnes, P. granulosum, and P. avidum were protective, while P. acidi-propionici and P. lymphophilum were ineffective. The protective effect proved to be in the cell wall fraction. Attempts were made to elucidate possible mechanisms of the protection using both effective and ineffective strains. The results strongly suggest that induction of interferon rather than activation of macrophages and natural killer cells by Propionibacterium pretreatment plays a crucial role, directly or indirectly, in protection against infection by herpes simplex virus. Propionibacterium only moderately protected newborn mice against HSV-2 infection.

Suppression of natural killer activity in human blood and bone marrow cultures by bone marrow-adherent OKM1-positive cells

Maintenance and regulation of natural killer (NK) cell activity in human bone marrow cultures were studied using K562 leukemia cells as targets. Culture of bone marrow cells in medium supporting long-term generation of myeloid cells resulted in a rapid loss of NK activity in 1-3 days. In contrast, antibody-dependent cytotoxicity to an NK-resistant tumor was maintained for more than 7 weeks. Horse serum, a component of the myelopoietic culture medium, was found to diminish NK cytotoxicity of blood and bone marrow cultures whereas hydrocortisone supplement did not. In addition, an adherent cell is present in bone marrow which greatly inhibits NK activity. Nonadherent bone marrow cells exhibited higher cytotoxicity than unfractionated cells at all days of culture; adherent cells were not cytotoxic to K562. Purified adherent marrow cells inhibited the cytotoxic capacity of nonadherent blood or marrow mononuclear cells during coculture. Indomethacin, an inhibitor of protaglandin synthesis, augmented levels of NK activity in cultures of bone marrow cells, indicating that macrophages may be suppressing this effector function via prostaglandins. Further identification of the adherent suppressor cells came from experiments in which suppression was prevented by treatment of the adherent cells with monoclonal OKM1 antibody plus complement. This study shows that bone marrow-adherent OKM1-positive cells, presumably macrophages, negatively regulate NK activity, and it defines conditions for analysis of the generation and/or positive regulation of NK cells in human bone marrow.

Intrapleural administration of OK432 in cancer patients: activation of NK cells and reduction of suppressor cells

Twelve patients with carcinomatous pleural effusions were treated with single intrapleural (i.pl.) administration of OK432 on day 0 and the effects of i.pl. OK432 on natural killer (NK) cell activity were followed on day 7. Two patients showed no clinical evidence of therapeutic benefit from i.pl. OK432. In the other 10 patients, pleural effusions and/or tumor cells in the effusions had decreased or disappeared by day 7. NK cell activity was markedly low or absent in pleural effusions of untreated patients due to the presence of adherent effusion cells capable of suppressing the maintenance and interferon-induced augmentation of NK cell activity. I.pl. injection of OK432 resulted in enhancement of NK cell activity and abrogation of NK suppressor cell activity in the effusions. On the other hand, blood NK cell activity was not consistently altered by i.pl. OK432. In vitro treatment of effusion mononuclear cells from untreated patients with OK432, but not with interferon, augmented NK cell activity. In addition, adherent effusion cells of untreated patients lost their NK suppressor function following in vitro OK432 treatment. These results suggest that i.pl. administration of OK432 will result in augmentation of NK cell activity and reduction of NK suppressor cell activity in pleural effusions, which could be responsible for the antitumor activity of i.pl. OK432.

Augmentation of NK activity by Corynebacterium parvum fractions in vivo and in vitro

Biochemically modified whole cell preparations and derived fractions of Corynebacterium parvum (C. parvum) were evaluated for the ability to augment natural killer cell cytoxicity in vivo and in vitro in rats. Unfractionated C. parvum enhanced peritoneal cell (Pc) NK activity in a dose dependent fashion. This activity appeared to be enriched in insoluble light residue material obtained from hot phenol water extraction. Enhancement of Pc cytotoxicity was significantly greater at all time points tested in rats injected with light residue when compared to rats injected with comparable amounts (by dry weight) of unfractionated organisms. In addition, pyridine extractable material and HCl modified preparations were capable of boosting Pc NK activity following intraperitoneal (I.P.) injection. Periodate treatment abrogated C. parvum's ability to boost Pc cytotoxicity and insoluble residue material obtained from pyridine extraction was likewise devoid of NK-enhancing properties. Culture of rat spleen cells overnight with unfractionated C. parvum, light residue and pyridine residue materials enhanced NK cytotoxicity whereas HCl and periodate modified whole cell preparations as well as phenol and pyridine extractable material were incapable of boosting cytotoxicity in vitro. In vitro augmentation by culturing with light residue was dependent on the presence of adherent cells in rat spleen cell populations. Pyridine extracts boost cytotoxicity in vivo and have no effect in vitro while the opposite is true of pyridine residue material suggesting different mechanisms of NK augmentation by C. parvum between in vitro and in vivo systems.

Antitumor activity of living or killed Brucella: modification of the non-specific cytotoxic effector cells

At various times after injection of living or killed smooth (S) or rough (R) Brucella abortus mice received a graft of the semi-allogenic EL4 lymphoma and their survival was studied. In parallel, the NK activity of spleen and peritoneal cells, the level of serum interferon (IFN), and the cytotoxic activity of peritoneal macrophages were investigated. Protection against the lymphoma lasted longer after injection of R organisms than after S. The parallelism between the in vivo resistance to El4 lymphoma and the augmentation of NK and macrophage activity was satisfactory with R but not with S. IFN production did not seem to be correlated with R antitumor activity. The antitumor effect of Brucella cannot therefore be simply explained on the basis of modification of the non-specific cytotoxic effector mechanisms.

Natural killer cells in human solid tumors

Natural killer (NK) cells have been studied in human neoplastic diseases in an effort to assess the role of these cells in the control of human neoplasia and to monitor the effects of therapeutic regimens expected to affect this reactivity. NK activity measured against susceptible cell lines is usually somewhat depressed in patients bearing advanced solid tumors, but not at early disease stages. Lymphoid cells associated with solid tumor tissues or effusions have usually low NK cytotoxicity, with considerable differences among histologic types (e.g., nasopharyngeal carcinoma versus other tumors) or at different sites involved by the same tumor (e.g., peritoneal effusions versus solid lesions in ovarian carcinoma). The low levels of NK activity of tumor-associated lymphoid cells are primarily related to a low frequency in the relevant effector cells at the tumor site, although suppression of the in vitro maintenance of cytotoxicity by in situ macrophages and lymphocytes has been described in a few patients. Treatment with immunopharmacologic agents, interferons in particular, has been reported to augment NK activity in cancer patients, but it is unclear how blood NK activity relates to tissue levels of this reactivity. Limited evidence indicates that blood NK levels need not be representative of the activity of tumor associated lymphoid cells. Most studies on NK cells in human neoplasia have dealt with reactivity against susceptible tissue culture lines, but freshly isolated human tumors are generally relatively resistant to these effector cells, particularly when autologous lymphoid cells are used. The resistance of fresh human neoplastic cells to NK activity has not been studied extensively and, together with the poor localization at the tumor site of NK effectors, it represents a major difficulty in envisaging a role for these cells in the control of established human neoplasia.

Rat macrophages inhibit natural killer (NK) cell activity against adherent growing target cells

Peritoneal as well as peripheral blood, but not spleen macrophages inhibit natural killer (NK) cell activity directed against adherent growing target cells. Inhibition was observed with macrophages (Mø): spleen cell ratios as low as 0.01:1. It was independent from the activation status of Mø and was not MHC restricted. With respect to the mechanism, cell contact was essential. A cold target mechanism, reflected by some binding, but not killing, of NK cells by Mø was of minor influence. Spontaneously by Mø released soluble mediators could be excluded, nor was any soluble mediator released upon contact of Mø with spleen cells, but NK activity could be partly inhibited by supernatants from cocultures of Mø with adherent growing target cells.

Kinetics of immunosuppression of sporozoite-induced immunity by Mycobacterium bovis BCG

The data reported in this study demonstrate that the vaccination of NIH/Nmri mice with viable Mycobacterium bovis BCG organisms induces a state of immunosuppression that renders the recipient animals incapable of a protective immune response to the malaria sporozoite vaccine. The expression of this altered protective immune response is dependent upon the dosage of the two live vaccines, as well as upon the sequence of their administration. Data presented here show that the skin test responses (Arthus and delayed type) of BCG-vaccinated mice do not correlate with the suppression of sporozoite immunity. Evidence is also presented to support the hypothesis that the abrogated immune response to sporozoite vaccination induced by BCG is a result of a loss of immunological memory.

Appearance of a cell surface antigen associated with the activation of peritoneal macrophages in mice

A relatively large population of murine peritoneal exudate macrophages induced with viable BCG or heat-killed Corynebacterium parvum was stained by the antiserum prepared against purified gangliotetraosyl ceramide (asialo GM1), while only a small population of peritoneal resident macrophages or peritoneal exudate macrophages induced with proteose peptone was stained. The cytotoxicity assay of those macrophages with anti-asialo GM1 plus complement supported these results. Peritoneal macrophages induced with BCG or C. parvum showed strong cytotoxicity for EL4 cells in vitro, while resident or peptone-induced peritoneal macrophages showed no cytotoxicity. BCG- or C. parvum-induced peritoneal cells contained both NK cells and cytotoxic macrophages, and either in vivo or in vitro pretreatment of the cells with anti-asialo GM1 and complement abolished the activities of both types of cells. Peptone-induced peritoneal macrophages incubated with lymphokines (LK) or lipopolysaccharide (LPS) were cytotoxic for EL4 cells and contained an increased number of cells stained by anti-asialo GM1. The cytotoxicity of these in vitro activated macrophages was reduced by treatment with anti-asialo GM1 plus complement. When peptone-induced peritoneal macrophages were incubated with LK, the number of cells stained by anti-Ia antiserum increased, but the number did not increase when the macrophages were incubated with LPS. Pretreatment of peptone-induced macrophages with anti-asialo GM1 plus complement did not affect the ability of the macrophages to be activated by LK. These results taken together strongly suggest that the antigen(s) reactive with anti-asialo GM1 is expressed on the cell surface of cytotoxic peritoneal macrophages in mice.

Corynebacterium parvum prevents immunization to admixed irradiated tumor cells by a local process

Immunization of mice with 10(6) irradiated LSTRA murine leukemia cells (LX) induced weak immunity to subsequent tumor-cell challenge. Admixture of low doses (1.4-14 micrograms of C. parvum with the LX usually augmented the immunity. Higher doses (1,400-7,000 micrograms) of admixed C. parvum not only failed to augment immunity, but prevented immunization by the contained LX. We investigated the mechanism by which 1,400 micrograms of C. parvum mixed with 10(6) LX prevents immunization by the LX. The inhibitory effect was a function of the ratio of C. parvum to tumor cells. Injection of 1,400 micrograms C. parvum, alone or mixed with the LX, did not prevent immunization by LX given simultaneously at a separate site. Injection of C. parvum, alone or mixed with the LX, did not prevent immunization by LX injected simultaneously at a separate site sharing a common lymph-node drainage area. The high dose of C. parvum prolonged retention of radiolabelled LX at the injection site and decreased the rate of distribution of the LX to other organs, particularly the spleen. These results indicate that a high dose of C. parvum prevented immunization through a localized process at the injection site.

Analysis of low natural killer cell activity in 89Sr-treated mice

Treatment of mice with the long-lived bone-seeking radioisotope 89Sr results in the selective irradiation and destruction of the bone marrow. This is accompanied by a marked reduction in natural killer cell activity against YAC-1 lymphoma [NK(YAC-1)]. To test for the presence of cellular suppressors of NK(YAC-1) in 89Sr-treated mice, in vitro and in vivo cell mixture protocols were used. In vitro, we did not observe any specific inhibitory effect of spleen cells from 89Sr-treated mice on NK(YAC-1) activity of normal spleen cells. The NK(YAC-1) activity of 89Sr-treated mice, measured in vivo by their ability to clear radiolabeled YAC-1 cells from the lungs, was impaired. However, spleen cells from 89Sr-treated mice, when adoptively transferred with normal spleen cells, failed to inhibit the NK(YAC-1) activity of the latter in the lung clearance assay. Further, when normal spleen cells were injected into 89Sr-treated mice, the ability of the transferred cells to mediate in vivo activity was not suppressed in the 89Sr-treated host. These experiments support the suggestion that the low NK(YAC-1) activity in 89Sr-treated mice is not mediated by suppressor cells, but may be due to the destruction of the marrow microenvironment which is essential for the generation of functional NK(YAC-1) cells.

Cytotoxic cells induced after Chlamydia psittaci infection in mice

The ability of spleen cells from Chlamydia psittaci-infected mice to lyse C. psittaci-infected and uninfected target cell monolayers was studied. The cytotoxicity assay used was a terminal label method in which the number of adherent target cells surviving the interaction with effector cells was determined by measuring the uptake of [3H]uridine by such cells. It was observed that in the first few days postinfection (3 to 5), spleens contained cells that lysed infected and uninfected targets with equal efficiency. Subsequently, infected targets were killed primarily. The activity of effector spleen cells for infected targets continued, although at a reduced level, beyond 21 days postinfection. Intact effector cells were required since a disruption by sonication resulted in a loss of cytotoxicity. The enhanced killing observed with infected targets was also observed when target cells were sensitized with heat- or UV-inactivated C. psittaci. This study suggests that the induction of cytotoxic cells after C. psittaci infection may contribute to the ability of the host to control multiplication of the microorganism.

Analysis of natural killer activity and antibody-dependent cellular cytotoxicity in healthy volunteers and in patients with primary lung cancer and metastatic pulmonary tumors

To clarify the contribution of ADCC and NK activities to host immune response against cancer, the characteristics of cells mediating these activities were examined in the peripheral blood lymphocytes of normal volunteers, and the changes of these activities were also evaluated in patients with lung cancer and metastatic pulmonary tumors before and after chemotherapy. OAT cells derived from small cell carcinoma of the lung and K-562 cells derived from erythroleukemia were used as target cells of ADCC and/or NK assay. ADCC and NK activities were not changed according to age, sex, and blood type. Mild and marked personal difference were observed in ADCC and NK activity, respectively. These activities were also influenced by environment. ADCC and NK activities of normal adult volunteers were diversely correlated at the coefficient of gamma-0.426. NK activities were high against K-562 and CCRF-CEM cells, and low against BALL and OAT cells. NK activity against K-562 cells was strongly inhibited by K-562 or CCRF-CEM cells with high NK sensitivity, on the other hand, it was slightly inhibited by OAT and BALL cells with low NK sensitivity. NK activity against OAT cells was strongly inhibited by OAT, K-562 and CCRF-CEM cells, but not inhibited by BALL cells. The effector cells mediating NK activity were identified as non-adherent, E-receptor-positive, Fc-receptor-positive small lymphocytes. NK activity was not decreased before chemotherapy in patients with stage III primary lung cancer and metastatic pulmonary tumors. It was decreased only in patients of bad performance status, and it was significantly decreased in all patients after chemotherapy. ADCC also exhibited the tendency to decrease after chemotherapy in tumor-bearing patients. The recovery of NK-activity after chemotherapy well correlated with the effect of chemotherapy.

Role of natural killer cells in control of cancer metastasis

There is a close association between levels of natural killer (NK) cell activity and the ability of the host to eliminate circulating tumor cell emboli. Mice that exhibit low levels of NK-cell-mediated cytotoxicity (3-week-old syngeneic mice, 3-week-old allogeneic nude mice, cyclophosphamide- or beta-estradiol-treated mice, and beige mice) also exhibit enhanced survival of tumor cells in the vascular bed of the lung and increased incidence of pulmonary tumor metastasis. Conversely, hosts with high NK cell activity (adult nude mice and syngeneic mice treated with NK-cell-stimulating biological response modifiers (BRM) ) are very resistant to metastasis. Lymphoid adoptive transfer studies have shown that the effector cell responsible for the antimetastatic activity is the NK cell. In these studies, NK cells were highly effective in destroying circulating tumor cells before their extravasation into the organ parenchyma, whereas they exerted only a minimal inhibiting effect on already established micrometastases. The ability to activate NK cells selectively (without subsequently inducing suppressor macrophages) provides a valuable tool for the evaluation of the role of activated NK cells in therapy of tumor metastasis. The validity of this approach is supported by the finding that NK cells activated by BRM are effective in killing, both in vivo and in vitro, solid tumor cells that developed NK-cell-resistance as a result of adaptive growth in vivo or selection during the metastatic process. An understanding of the mechanisms that regulate NK cell activation or suppression as well as elucidation of the circulatory patterns and anatomical compartmentalization of activated NK cells will help achieve a sustained systemic and/or in situ activation of NK cells which may prove effective in the control of cancer metastasis.

Activation of natural killer (NK) cells in vivo with H-2 and non-H-2 alloantigens

Intraperitoneal inoculation of allogeneic lymphoid cells rapidly activates cytotoxic cells in the peritoneum which are nonadherent and express the NK-1, asialo-GM1, and Thy-1 antigens. Allogeneic spleen cells were very efficient at activating these natural killer (NK) cells, while allogeneic thymocytes were much less effective. Heat-killed allogeneic cells or sonicates also could augment NK activity.--Incompatbility at H-2K, H-2T-A, or H-2D readily evoked NK cell activity, while H-2S- and H-2I-E/C-associated a disparities did not. Non-H-2 differences also stimulated NK activity and augmentation was particularly evident in the Mls-disparate combinations. Thus, the same alloantigens which efficiently activate T cells also activate NK cells.

Protection of mice against mouse hepatitis virus by Corynebacterium parvum

C57BL/6 mice that are highly susceptible to infection with mouse hepatitis virus type 3 were protected against intraperitoneal viral infection by simultaneous intraperitoneal injection of Corynebacterium parvum. No protection was observed when C. parvum was given intravenously or when it was injected intraperitoneally 3 days before viral infection. Protective effects were, however, consistently found when C. parvum was given 2 h before or 2 h after viral infection. Activity was seen only against 10 50% lethal doses and not against 100 50% lethal doses. C. parvum also caused a significant decrease of virus type 3. These data suggest a direct effect of C. parvum on virus-susceptible cells. Injection of C. parvum in mice caused activation of natural killer (NK) cells and of interferon production. However, these two effects were equally demonstrable at high and low doses of C. parvum, whereas protection against mouse hepatitis virus type 3 was not demonstrable at low doses of C. parvum. Thus, antiviral protection may be dissociated from activation of NK cells and induction of interferon.

Hybrid resistance to EL-4 lymphoma cells. II. Association between loss of hybrid resistance and detection of suppressor cells after treatment of mice with 89Sr

(C57BL/6 X DBA/2)F1 hybrid (B6D2F1) mice resist the growth of parental-strain (B6) EL-4 lymphoma cells inoculated intraperitoneally; that is, B6D2F1 mice survive longer than B6 mice and do not develop ascites. As compared with B6 mice, B6D2F1 mice have higher levels of natural killer (NK) activity against 51Cr-labelled EL-4 cells in their lymphoid organs. B6D2F1 mice treated with 89Sr lose NK activity for certain lymphoma cell targets, e.g. YAC-1, but NK(EL-4) function is usually intact. However, 89Sr-treated mice had lost hybrid resistance to EL-4 cells in vivo, as determined by survival by irradiated or unirradiated EL-4 cells, Corynebacterium parvum, or polyinosinic:polycytidylic acid (pI:pC) in spleens of normal B6D2F1 mice, but NK(EL-4) activity was depressed within 3 days by such treatment in B6D2F1 mice previously injected with 89Sr. Suppressor cells for NK(EL-4) but not for NK(YAC-1) effectors were easily detected in spleens of 89Sr-treated mice "challenged' with C. parvum. Thus, agents capable of stimulating NK cell function in normal mice may lead to suppression of that activity in mice depleted of marrow-dependent cell function by 89Sr. Spleen cells of 89Sr-treated B6D2F1 mice were also unable to generate anti-EL-4 cytotoxic T lymphocytes in a cell-mediated lympholysis system; this defect appeared also to be mediated by suppressor cells. Lymphoid cells depleted by 89Sr-induced marrow aplasia may have two functions in host defences against tumours (especially lymphomas): they may lyse tumour cells directly and they may "down-regulate' suppressor cells capable of inhibiting other "natural' or "induced' immune functions.

Effect of route of Mycobacterium bovis BCG administration on induction of suppression of sporozoite immunity in rodent malaria

Intravenous immunization of mice with 16,000, 60Co--gamma-irradiated, attenuated sporozoites produced solid immunity to sporozoite-induced malaria when the mice were challenged 21 days after immunization. In contrast, mice injected by various routes with 10(7) viable units of Mycobacterium bovis (BCG) before immunization with irradiated sporozoites were not completely immune to challenge. The extent of reduced protection against viable sporozoites demonstrated with these animals was dependent upon the injection route mycobacteria. The intravenous administration of BCG induced the greatest degree of suppression, followed by the intraperitoneal and subcutaneous routes. BCG injected intramuscularly before sporozoite immunization did not suppress development of immunity. In contrast, mice injected with BCG after immunization with attenuated sporozoites exhibited a lesser degree of suppression. In these animals, only the intravenous injection of mycobacteria reduced immunity.

Suppression of activity of mouse natural killer (NK) cells by activated macrophages from mice treated with pyran copolymer

Treatment of young mice with pyran copolymer caused a substantial decrease in natural killer (NK) cell activity at 7 days. The decrease in cytotoxicity was associated with the presence of splenic suppressor cells, capable of inhibiting in vitro the NK activity of spleen cells from normal mice. The suppressor cells appeared to be macrophages, being plastic-adherent, phagocytic and radioresistant, and lacking demonstrable Thy 1.2 antigen. Sonicates or culture supernatants of adherent spleen cells from pyran-treated mice were also able to inhibit NK activity, suggesting that suppressor cells act by release of soluble factors.