Role of humoral factors in the regulation of hemopoiesis in stress]

The change of 11-1, IL-3, CSA concentrations in adherent and nonadherent bone marrow cells condition medium at stress were investigated. The activation of bone marrow hemopoiesis was registered at mice after immobilization stress. The number of CFU-GM increased on 1, 4 and 5 day after stress. Maximum of CSA in adherent and nonadherent cells conditioned medium was observed on day 4, 6 or 2, 5 respectively. The increasing of 11-3 activity in culture of nonadherent bone marrow cells was registered from day 1 and mount to maximum at 4-5 days. The increasing of 11-1 level in culture of adherent bone marrow cells was found at 1 and 4 days.     

Plasmodium yoelii: the thymus-dependent lymphocyte in mice immunodepressed by malaria

Euthymic mice, athymic nude mice, and mice treated with antithymocyte serum were infected with Plasmodium yoelii and immunized 10 days postinfection with pneumococcal polysaccharide (SSSIII). As a control, uninfected mice were also immunized with SSSIII. Splenic plaque-forming cells as well as serum antibody titers to SSSIII were measured 5 days after immunization. In infected euthymic mice, both plaque-forming cells (PFC) and serum antibody were severely depressed. In contrast, plaque-forming cells and serum antibody were approximately normal in infected nude mice and in infected mice treated with antithymocyte serum. Splenic adherent cells from infected euthymic mice failed to function as accessory cells in the in vitro antibody response to a second antigen, the sheep erythrocyte. Moreover, they lacked suppressor activity when cultured with spleen cells from uninfected mice. In contrast, adherent spleen cells from infected mice treated with antithymocyte serum displayed accessory cell function.     

Adherent cells (macrophages?) in tumor-bearing mice suppress MLC responses

The spleens of mice bearing transplanted methylcholanthrene (MCA)-induced fibrosarcomas (MCA-1425 and MCA-1460) were shown to contain cells capable of suppressing the generation of cytolytic T lymphocytes (CTL) in mixed leukocyte cultures (MLC). The suppressive activity was first detected 21 days after tumor transplantation. No suppression was seen with lymph node cells taken at the same time as the spleen cells. The cells responsible for the suppressive activity were adherent to nylon wool and plastic dishes and they were not lysed by anti-T-cell serum plus complement. The suppressor cells were phagocytic and were resistant to irradiation (3000 rads) in vitro. Spleen cells from tumor-bearing nude mice were as suppressive as were spleen cells from tumor-bearing conventional mice. We conclude from these findings that T cells were not involved either as inducers or as effectors of the suppression observed, although the responsible adherent cells may have exerted their effect by interacting with a T-suppressor cell population in the MLC mixtures. While spleen cells of tumor-bearing mice were suppressive when added at any time during the first 4 days of a 5-day MLC, they showed no effect on the cytotoxicity of fully differentiated CTL. Indomethacin reversed suppression, suggesting that prostaglandins may have been involved.     

Enhancing effect of IFN-gamma on helper T cell activity and IL 2 production

A single injection of young murine immune interferon (IFN-gamma) in young (3 mo) or old (14 to 24 mo) mice 3 days before carrier-priming significantly enhances helper T cell activity of their spleen cells. Maximal enhancement is attained when IFN-gamma is injected once immediately before priming or for 4 consecutive days from the time of priming. Helper activity for anti-TNP antibody response was titrated in vitro by adding graded numbers of spleen cells from HRBC-primed mice of a given age to cultures containing a constant number of spleen cells from 3-mo-old normal mice and TNP-HRBC. When T cell-enriched spleen cells from HRBC-primed young or old mice, uninjected or injected with IFN-gamma, were separated by nylon wool filtration into passed (Thi) and adherent (Th2) cells, the helper activity of both T cell subpopulations was found to be enhanced by IFN-gamma injection. Helper activity of purified Th1 and Th2 cells was also increased by their in vitro preincubation with IFN-gamma. Furthermore, interleukin 2 (IL 2) production by mitogen-activated spleen cells from young and old mice is enhanced by addition of IFN-gamma to cultures. These data altogether indicate that IFN-gamma plays an important role in immunoregulation of helper T cell activity.     

Functional maturation of murine B lymphocyte precursors. I. Selection of adherent cell-dependent precursors from bone marrow and fetal liver

A cell culture assay is described which is suitable to explore interactions between cells of the bone marrow (BM) microenvironment on one side and B lymphocyte progenitors on the other. First, a heterogeneous adherent BM (aBM) cell population was established on Cytodex 1 microcarriers. Then, adherent cell and surface IgM+(sIgM+) cell-depleted BM precursors or adherent cell-depleted day 12 fetal liver cells were added. The generation of B cells in these cultures was monitored by staining with fluorochrome-labeled anti-mu-chain antibody and by lipopolysaccharide (LPS) induction of protein A plaque-forming cells at limiting dilution. In the absence of aBM cells, some B cells arose after 24 hr from BM precursors but not from day 12 fetal liver cells. With aBM cells, BM precursors gave rise to a distinct second wave of B cells starting after 5 days of culture. When fetal liver cells were cultured on aBM cells, B cells appeared after a delay of 4 to 5 days. By using Ig allotype-congenic mouse strains (C.AL 20, BALB/c) and an allotype-specific plaque assay, we established that mature B cells originate from the putative progenitors and not from the aBM cell population. In an attempt to eliminate the aBM cell-independent progenitor subset, mice were pretreated with 5-fluorouracil 5 days before BM cells were collected. The remaining cells still contained B cells, but the frequency of c mu+ sIgM- pre-B cells was less than 10(-5). Remaining B cells were removed by anti-mu panning. In cultures of this precursor cell population, LPS-responsive B cells appeared after a delay of about 1 wk, and their generation was totally aBM cell-dependent and was maintained for more than 2 wk.     

Induction of interferon production in mouse spleen cell cultures by corynebacterium parvum.

Spleen cells of CS7BL/6 mice produced considerable amounts of interferon (IF) in vitro when tested 5 to 20 days after injection of killed Corynebacterium parvum. Interferon was also produced when C. parvum was added in vitro to spleen cell cultures of previously untreated mice. High levels were detected after 1 day of culture with some increment during subsequent days. In a number of experiments IF was also produced in untreated control cultures but only after prolonged cultivation and not after 1 day. The highest levels of IF were usually obtained when spleen cells of C. parvum-treated mice were challenged with additional C. parvum in vitro. The IF induced by C. parvum shared certain physicochemical properties with a tested immune IF and was not neutralized by an antiserum raised against a type I IF. Spleen cells of nu/nu mice and spleen cells treated by anti-θ serum plus complement did not differ from their respective controls, indicating that production of IF did not require mature T lymphocytes. Removal of B lymphocytes by nylon wool columns abolished the capacity of spleen cells to produce IF. When spleen cells were freed of adherent cells by the use of plastic surfaces, they no longer produced IF. Peritoneal exudate macrophages (PEC), which by themselves did not produce IF, in small numbers reconstituted nonadherent spleen cells. Nylon column-treated spleen cells, however, could not be restored by PEC. It is concluded that IF upon challenge with C. parvum is produced by B lymphocytes and requires the help of macrophages.     

Immunomodulating activity of meningococcal antigens

A preparation of meningococcal antigens (MA) extracted in CaCl2, and containing mostly outer membrane proteins, was strongly mitogenic for murine B lymphocytes. Given to mice in vitro, MA markedly impaired subsequent in vivo T-cell responses of splenocytes. Suppression of normal T splenocytes in vitro occurred with both adherent (Ad) and nonadherent (NA) splenocytes from MA-sensitized mice. B cells were much less affected by the suppression induced by MA, and only Ad cells could convey in vitro the low level impairment of B-cell proliferation. Strong T-cell suppression associated with a B-cell mitogen is also produced by bacillus Calmette-Guérin (BCG) and Corynebacterium parvum. The possible role of these phenomena in meningococcal disease is discussed.     

Suppressor cells as an agent of immune facilitation. II. Adoptive transfer of passively induced enhancement of allografted tumors

CBA mice injected intravenously with CBA anti-A/J spleen cell antiserum, and challenged subcutaneously 24 hr later with A/J-derived sarcoma 1 (Sa 1) develop progressive tumors. “Normal” CBA mice (i.e., injected with normal CBA serum or noninjected) reject the allograft within 20 days. Spleen cells taken from mice 20–35 days after the injection of antiserum and Sa 1 challenge can specifically transfer the ability to enhance tumor growth when injected into 200 rad irradiated recipients. Spleen cells taken 8 days after antiserum and Sa 1 challenge cannot transfer suppression. The induction of suppressor cells requires both antiserum treatment and Sa 1 challenge. Serum from suppressed mice, and from control mice that are rejecting their tumors, can also transfer suppression but only when taken 20–35 days after treatment. The suppressor cells function most effectively when transferred at the time of tumor challenge, however, they also inhibit the rejection of Sa 1 when mixed with nylon-wool purified sensitized T cells. Suppressor cells are both nylon-wool nonadherent and adherent. Further purification of the column-enriched cells using antiimmunoglobulin or anti-Thy 1.2, plus complement, suggests that both T and B cells can suppress. The mixed lymphocyte response (MLR) of spleen cells from mice challenged only with Sa 1 is inhibited 8 days after challenge. A secondary response is obtained at 20–27 days. In contrast, the MLR from antiserum and Sa 1-treated mice 8 days after challenge resembles a secondary response. By 20–27 days mice with progressive tumors have only a primary-like response. In the present experimental situation, mitomycin-treated spleen cells from antiserum and Sa 1-treated mice cannot significantly inhibit the MLR of normal cells.     

Decrease in tumorigenic activity of murine hepatoma cells after treatment with antioxidants and melatonin

We studied the effect of antioxidants such as N-acetylcysteine (NAC, 10 mM) and alpha-lipoic acid (ALA, 1.25 mM) and of the hormone melatonin (1 microM) on the ability of murine hepatoma cells MH22a to develop tumors in syngenic mice (C3HA) after subsutaneous injection. Tumor formation and development slowed down and mouse mortality decreased when the injected cells were pretreated by NAC, ALA or melatonin during 20 h. Melatonin had the most marked effect. Tumors appeared in 100 % cases after 10 days in control mice when untreated cells had been injected; injection of cells pretreated by NAC or ALA resulted in tumor formation only in 40 and 53 % of mice, respectively. When cells were pretreated with melatonin the tumors appeared only in 18-20 days after injection. Until the end of the observation (36 days) 67 % of control mice died, but when the cells were pretreated by NAC or ALA mouse death-rate was 20 and 53 %, respectively. In the case of melatonin we did not observed any dead mice at all. We showed that treatment by antioxidants delayed (NAC) or completely inhibited (ALA) cell cycle of hepatoma cells. Cell cycle was restored after removal of the antioxidants. Melatonin did not change cell cycle phase distribution. We conclude that there is no direct correlation between loss of tumorigenic properties and changing of proliferative activity of hepatoma cells. Different mechanisms of antioxidants and melatonin action resulting in transient tumor phenotype normalization are discussed.     

Anti-tumor cytostatic mechanism and delayed-type hypersensitivity against a syngeneic murine tumor. Comparison between neonatally thymectomized mice and congenitally athymic nude mice

We studied the anti-tumor mechanism against a syngeneic tumor using a BALB/c-MA tumor system by cytolysis and cytostasis assays in vitro comparing mice neonatally thymectomized at 1 day or 7 days after birth (NTx-1, NTx-7), sham-operated (sham) mice, and congenitally athymic nude BALB/c mice. NTx-1 mice showed more rapid tumor growth and a slightly lower degree of strong cytostatic activity in peritoneal exudate cells (PEC) than NTx-7 or sham mice. Nude mice showed more rapid MA growth than NTx-1 mice and no cytostatic activity in PEC. After immunization with mitomycin C-treated MA (MMC-MA), NTx-1 mice acquired an immunoprophylactic capacity against MA and showed cytostatic activity and delayed footpad reaction (DFR) to MA, however, nude mice showed no acquisition of such an immunity, or cytostatic activity, or DFR to MA. These differences between NTx-1 and nude mice could be well-explained by less capacity of nude mice to produce a macrophage-activating factor, which activates macrophages to exert cytostasis and DFR. However, NTx-1 mice could not reject MA by immunization with MMC-MA in CFA (MMC-MA/CFA), although such immunized sham mice could eliminate MA completely. Both PEC and spleen cells from Sham mice immunized with MMC-MA/CFA showed cytostatic activity, whereas NTx-1 mice showed cytostatic activity of the same level in PEC and less in spleen cells compared to Sham mice. Cytolytic activity was never detected throughout this study in a BALB/c-MA system. These data suggest that cytostasis plays an important role in antitumor immunity against a syngeneic MA tumor and that two types of cytostasis is included from the standpoint of thymus-dependency of ontogenic development, relatively low and high.     

Prostaglandin synthesis in spleen cell cultures of mice injected with Corynebacterium parvum.

Spleen cells of C57BL/6 mice produced high amounts of PGE in vitro when tested 5 to 10 days after injection of heat-killed C. parvum organisms. Little or no PGE was produced by spleen cells from untreated mice or from mice injected with a strain of coryneform bacteria that does not stimulate the lymphoreticular system of mice. Significant release of PGE from spleen cells of C. parvum injected mice could be detected as early as 30 min after initiating the cultures and maximal levels were usually seen after 48 hr. Treatment by indomethacin completely abolished this PGE production. Removal of the adherent population from the spleen cell suspension resulted in markedly decreased levels of PGE, but PGE release of the remaining population was never completely abolished. These data suggest that the cells responsible for most of the PGE synthesis in this system were adherent cells, presumably macrophages. The levels of PGE produced in spleen cells of C. parvum-treated mice were further increased by in vitro addition of C. parvum. This effect could also be observed after addition of zymosan particles indicating that it was not an immunologically specific effect. The reported data suggest that prostaglandins may represent important mediator molecules of the described immunostimulatory and immunosuppressive effects of C. parvum.     

Antibody formation in mouse bone marrow. IX. Peripheral lymphoid organs are involved in the initiation of bone marrow antibody formation.

Mouse bone marrow is barely capable of plaque-forming cell (PFC) activity during the primary response to sheep red blood cells (SRBC). However, during secondary-type responses, it becomes the major organ, containing IgM, IgG, and IgA PFC. In the present paper, the influence of splenectomy (Sx) upon the secondary bone marrow PFC response to SRBC was investigated. When previously primed mice were splenectomized just before the second intravenous (iv) injection of SRBC, the effect of Sx upon the height of the bone marrow PFC response was dependent on the booster dose. Sx just before a booster of 10⁶ SRBC iv almost completely prevented bone marrow PFC activity, whereas an iv booster dose of 4 × 10⁸ SRBC evoked a normal IgM, IgG, and IgA PFC response in Sx mice. Apparently low doses of iv administered antigen require the spleen in order to evoke antibody formation in the bone marrow. Experiments with parabiotic mice, consisting of Sx and sham-Sx mice, showed that this facilitating influence of the spleen upon bone marrow antibody formation occurs via the blood stream. In a subsequent study, it was investigated whether the spleen is required throughout the bone marrow PFC response or only during the few days of the initiation phase. Therefore, mice were splenectomized at different intervals after a booster injection of 10⁶ SRBC iv. It appeared that Sx 2 days after the booster injection could still prevent the normal bone marrow PFC activity, whereas Sx at Day 4 could no longer do so. Apparently, after an iv booster injection, the spleen is only required for initiation of the bone marrow PFC response and not for the maintenance of this PFC activity thereafter.     

Suppressive effects of monocytic cells and transforming growth factor-beta on natural killer cell differentiation in autoimmune viable motheaten mutant mice.

Viable motheaten (mev) mice are homozygous for a recessive single gene mutation at chromosome 6. These mice develop numerous inflammatory and arthritic syndromes and exhibit abnormal B cell functions as well as lower T and NK cell activity. In this study, the differentiation of NK cells in mev mice was examined to elucidate the underlying basis for decreased NK activity. Although NK cells appear to be present in mev mice, their activity was demonstrable only when the spleen cells were enriched by nylon wool passage. Similarly bone marrow cells from these mice could be shown to contain precursors of NK cells when they were passed over nylon wool and transplanted into irradiated recipients. The adherent cells from both the spleen and bone marrow of mev mice suppressed the differentiation of NK cells from normal splenic populations. These suppressive adherent cells were F4/80(+), AsGm-1(+), Qa-5(+), and NK-1.1(+). They were not cytolytic when cultured in IL-2. Antibodies to a number of cytokines, such as IFN-alpha, -beta, and gamma, or TNF-alpha, could not reverse the suppressive effect of the adherent cells. Addition of anti-TGF-beta antibody could, however, overcome the suppression, suggesting that TGF-beta was partly responsible for the defective NK differentiation in the mev mice.     

FGF21 induces autophagy‐mediated cholesterol efflux to inhibit atherogenesis via RACK1 up‐regulation

Fibroblast growth factor 21 (FGF21) acts as an anti‐atherosclerotic agent. However, the specific mechanisms governing this regulatory activity are unclear. Autophagy is a highly conserved cell stress response which regulates atherosclerosis (AS) by reducing lipid droplet degradation in foam cells. We sought to assess whether FGF21 could inhibit AS by regulating cholesterol metabolism in foam cells via autophagy and to elucidate the underlying molecular mechanisms. In this study, ApoE^?/? mice were fed a high‐fat diet (HFD) with or without FGF21 and FGF21 + 3‐Methyladenine (3MA) for 12 weeks. Our results showed that FGF21 inhibited AS in HFD‐fed ApoE^?/? mice, which was reversed by 3MA treatment. Moreover, FGF21 increased plaque RACK1 and autophagy‐related protein (LC3 and beclin‐1) expression in ApoE^?/? mice, thus preventing AS. However, these proteins were inhibited by LV‐RACK1 shRNA injection. Foam cell development is a crucial determinant of AS, and cholesterol efflux from foam cells represents an important defensive measure of AS. In this study, foam cells were treated with FGF21 for 24 hours after a pre‐treatment with 3MA, ATG5 siRNA or RACK1 siRNA. Our results indicated that FGF21‐induced autophagy promoted cholesterol efflux to reduce cholesterol accumulation in foam cells by up‐regulating RACK1 expression. Interestingly, immunoprecipitation results showed that RACK1 was able to activate AMPK and interact with ATG5. Taken together, our results indicated that FGF21 induces autophagy to promote cholesterol efflux and reduce cholesterol accumulation in foam cells through RACK1‐mediated AMPK activation and ATG5 interaction. These results provided new insights into the molecular mechanisms of FGF21 in the treatment of AS.     

Renewal of natural killer cells in mice having elevated natural killer cell activity

The present study was designed to examined the dynamics of splenic natural killer (NK) cells under two conditions of enhanced NK cell activity: (1) CBA/J mice given polyinosinic-polycytidylic acid (poly-I:C), an NK-cell-enhancing agent, and 62) untreated athymic nude (nu/nu) mice. The 'total NK cell activity' of the spleen (percentage specific lysis corrected for changes in organ cellularity) increased 5-fold and 2.7-fold after poly-I:C treatment for 1 day and 4 days, respectively. An injection of hydroxyurea (HU), a cell-cycle-toxic drug, given together with either poly-I:C or saline to CBA/J mice resulted in both cases in a 25% reduction in total NK cell activity 1 day later. This suggests that the renewal rate of nondividing NK cells is similar in poly-I:C-treated and saline-injected mice, and that the NK-enhancing effect of poly-I:C is not due to a stimulation of proliferation among NK cell precursors. HU administered simultaneously with poly-I:C or saline for 4 days eliminated NK cell activity in both cases, indicating that spleen NK cell activity is mediated almost entirely by newly formed (less than or equal to 4 days) cells. In nude mice, NK cell activity was assayed at various intervals after an HU depletion period of 2 days. NK depletion was initially more rapid in nu/nu mice than in control (nu/+) mice, although equally profound, and the subsequent recovery of NK cell activity after cessation of HU was also more rapid than in control (nu/+) mice.(ABSTRACT TRUNCATED AT 250 WORDS)     

Epileptogenesis following Kainic Acid-Induced Status Epilepticus in Cyclin D2 Knock-Out Mice with Diminished Adult Neurogenesis

The goal of this study was to determine whether a substantial decrease in adult neurogenesis influences epileptogenesis evoked by the intra-amygdala injection of kainic acid (KA). Cyclin D2 knockout (cD2 KO) mice, which lack adult neurogenesis almost entirely, were used as a model. First, we examined whether status epilepticus (SE) evoked by an intra-amygdala injection of KA induces cell proliferation in cD2 KO mice. On the day after SE, we injected BrdU into mice for 5 days and evaluated the number of DCX- and DCX/BrdU-immunopositive cells 3 days later. In cD2 KO control animals, only a small number of DCX+ cells was observed. The number of DCX+ and DCX/BrdU+ cells/mm of subgranular layer in cD2 KO mice increased significantly following SE (p<0.05). However, the number of newly born cells was very low and was significantly lower than in KA-treated wild type (wt) mice. To evaluate the impact of diminished neurogenesis on epileptogenesis and early epilepsy, we performed video-EEG monitoring of wt and cD2 KO mice for 16 days following SE. The number of animals with seizures did not differ between wt (11 out of 15) and cD2 KO (9 out of 12) mice. The median latency to the first spontaneous seizure was 4 days (range 2 – 10 days) in wt mice and 8 days (range 2 – 16 days) in cD2 KO mice and did not differ significantly between groups. Similarly, no differences were observed in median seizure frequency (wt: 1.23, range 0.1 – 3.4; cD2 KO: 0.57, range 0.1 – 2.0 seizures/day) or median seizure duration (wt: 51 s, range 23 – 103; cD2 KO: 51 s, range 23 – 103). Our results indicate that SE-induced epileptogenesis is not disrupted in mice with markedly reduced adult neurogenesis. However, we cannot exclude the contribution of reduced neurogenesis to the chronic epileptic state.     

BCG-induced suppressor cells. I. Demonstration of a macrophage-like suppressor cell that inhibits cytotoxic T cell generation in vitro.

Spleen cells obtained from mice 5 to 40 days after infection with viable BCG organisms (BCG-spleens) were found to be unresponsive in vitro to both mitogenic and alloantigenic stimuli. Moreover, suppressor cells could be demonstrated in the spleens from these infected animals. When spleen cells from BCG-infected mice were added to either syngeneic or allogeneic normal spleen cells, the mixtures neither proliferated nor developed cytotoxic activity when cultured with alloantigen or with concanavalin A (Con A). The development of unresponsiveness post-infection paralleled the onset of suppressive activity. Spleen cells obtained from mice given heat-killed BCG were neither suppressive nor unresponsive. The suppressive activity of BCG-spleen cells was associated with an adherent, phagocytic cell that lacked membrane-associated Thy-1 antigen. Removal of this cell by passage through nylon wool columns resulted in a cell population that was no longer capable of suppression and that responded normally to alloantigen and to Con A. It would thus appear that BCG infection results in the development of a "suppressor" macrophage-like cell population within the spleen. The role of this cell type in regulation of the immune response in BCG-infected animals is as yet undefined.     

Effect of interleukin-18 on metastasis of mouse osteosarcoma cells

The effect of interleukin-18 (IL-18) on metastasis of highly metastatic LM8 mouse osteosarcoma cells was investigated using nude mice treated with anti-asialo GM1 serum to exclude anti-tumor actions of IL-18 through activation of T and natural killer cells. Injection of LM8 cells which do not express IL-18 receptor β into a tail vain resulted in the formation of pulmonary and hepatic metastatic foci. Daily injection of mice with IL-18 starting the fifth day from the cell injection had no significant effect on the number of metastatic foci, while five daily injections of IL-18 before and after the cell injection resulted in marked decreases. Culture of LM8 cells with IL-18 for 5 days before the injection into mice produced no significant effect on the number of pulmonary and hepatic metastatic foci. In contrast, pretreatment of mice with IL-18 for 5 days before the cell injection markedly decreased metastatic foci. The retention of LM8 cells in the lung 24 h after their injection was also reduced by the pretreatment of mice with IL-18. Serum obtained from mice pretreated with IL-18 for 5 days suppressed mobility of LM8 cells but IL-18 itself did not. These results suggest that IL-18 inhibits metastasis of LM8 cells partly by inducing a factor(s) in the host which suppresses cell mobility.     

Induction of cytotoxicity of peritoneal exudate cells by agrimoniin,a novel immunomodulatory tannin of Agrimonia pilosa Ledeb

Summary The cytotoxic activities of the PEC after an i.p. injection of agrimoniin, a tannin contained in Agrimonia pilosa Ledeb. were studied. The plastic nonadherent PEC had significantly higher NK cell activity than the untreated control, and the adherent PEC were cytostatic toward MM2 and MH134 cells. The adherent PEC did not cause tumor cell lysis by themselves, but were cytolytic against MM2 cells in the presence of anti-MM2 sera. In the course of these effects of PEC after the i.p. injection of agrimoniin, the augmentation of NK cell activity was the earliest reaction, reaching a peak at 2 days after the injection; then, cytostatic activity increased. The induction of antibody-dependent cell lytic activity was a later reaction, which reached a peak at 6 days after the injection. Abbreviations used: PEC, peritoneal exudate cells; NK cell, natural killer cell; ADCC, antibody-dependent cell-mediated cytotoxicity; PMN, polymorphonuclear leukocytes     

The in vitro killing of syngeneic cells by peritoneal cells from adjuvant-stimulated mice.

The cytotoxicity of peritoneal exudate cells from mice which had been injected with anaerobic coryneform organisms which have adjuvant activity was assessed by measuring the release of radioactive chromium from monolayers of whole mouse embryo cells. It was found that the peritoneal cells from adjuvant-stimulated mice were more cytotoxic than cells from normal mice. The increased cytotoxicity was present as early as 2 days after injection of the organisms, and was abolished by trypsin treatment of the peritoneal cells. The cytotoxic effect requires the presence of live peritoneal cells, and is more marked as the ratio of effector to target cells is increased. The plastic adherent cells of the peritoneal cell population are more effective in the cytotoxic reaction than are the non-adherent cells. The stimulated peritoneal cells can kill both syngeneic and allogeneic mouse embryo cells. Consideration is given to the possible mechanisms by which the increased cytotoxicity might be induced.