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B Bonavida

Publications and source records attributed to B Bonavida.

At least 109 records · Page 6Linked to original sources
PubMed1990

Sensitivity of ovarian tumor cells to effector cells generated by various biological response modifiers.

The sensitivity of freshly derived human ovarian tumors (FOT) to various allogeneic cytotoxic effector cells stimulated by recombinant interleukin 2 (rIL-2), recombinant interferon alpha 2 (rIFN-alpha 2), OK-432, and concanavalin A was examined using the 51Cr release assay. Peripheral blood lymphocytes (PBL) of normal female donors were used as source of effector cells. Incubation of PBL with these biological response modifiers for 24 h generated effector cells with high natural killer activity, and only 20% (1/5) of the FOT examined were susceptible to lysis. By contrast, 83% (5/6) of the FOT were sensitive to lymphokine-activated killer (LAK) cells generated by rIL-2. OK-432 and concanavalin A activation of PBL also generated cytotoxic cells, though the cytotoxic activity against FOT was much less than that obtained by LAK cells. The addition of OK-432 to LAK culture medium containing rIL-2 generated effector cells with higher cytotoxicity against FOT than cultures with IL-2 alone. However, the addition of rIFN-alpha 2 in LAK culture medium resulted in the generation of effector cells with lower cytotoxicity. The addition of rIL-2, rIFN-alpha 2, or OK-432 to LAK cells during the in vitro cytotoxicity assay had no significant effect. When FOT target cells were pretreated with OK-432 they became more sensitive to LAK than nontreated tumor cells. However, pretreatment with rIL-2 or rIFN-alpha 2 did not influence cytolysis. These results suggest that the generation of LAK cells in vitro using rIL-2 plus OK-432 may be a more effective way to prepare these cells for adoptive immunotherapy in the treatment of ovarian cancer.

Concanavalin A↗
PubMed1989

Activation of human peripheral blood-derived monocytes by OK-432 (Streptococcus pyogenes): augmented cytotoxicity and secretion of TNF and synergy with rIFN-gamma.

The biological response modifier OK-432 has been shown both to exert the enhancement of several immunological activities and to have a direct anti-tumor effect. The present study examines the immunopotentiating effect of OK-432 on peripheral blood monocytes (PBM) derived from normal humans. Monocyte activation was assessed by examining direct cell-mediated cytotoxic activity (CMC) and secretion of cytotoxic factors in the supernatant by the 51Cr release assay and secretion of tumor necrosis factor (TNF)-alpha detected by a sensitive radioimmunoassay. The OK-432-augmented activity was compared to that achieved by recombinant interferon-gamma (rIFN-gamma). Coculture of PBM with OK-432 overnight resulted in significant augmentation of CMC and secretion of cytotoxic factors and TNF in the supernatant. The effects observed were dose dependent and the resulting activity was much more pronounced than that achieved with an optimal concentration of IFN-gamma. The monocyte- and supernatant-mediated cytotoxic activities were in a large part attributed to TNF as both activities were inhibited by anti-TNF antibody. Several parameters of monocyte activation by OK-432 were examined. The kinetics of monocyte activation revealed that a short time exposure (2-6 hr) was sufficient for activation but maximal activation was detected after 18 hr. However, the kinetics of the cytotoxic assay were not shortened and 16-20 hr was necessary for optimal cytotoxic activity. Significant synergy was obtained when suboptimal concentrations of OK-432 and IFN-gamma were used. The synergy was noted in CMC, supernatant activity, and TNF concentration. These results demonstrate that OK-432 is a potent activator of monocyte cytotoxicity and also activates secretion of TNF. Also, OK-432 is a much more potent activator than rIFN-gamma. The synergy with OK-432 and IFN-gamma suggests that OK-432-mediated activation of monocytes takes place by a different mechanism than that mediated by rIFN-gamma. Thus, monocytes and products thereof may actively participate in the in vivo anti-tumor effect mediated by OK-432.

Biological Products↗
PubMed1989

Internucleosomal DNA cleavage precedes diphtheria toxin-induced cytolysis. Evidence that cell lysis is not a simple consequence of translation inhibition.

Diphtheria toxin (DTx) is an extremely potent inhibitor of protein synthesis. Cell death has been generally accepted as a straightforward effect of translation inhibition. Using human U937 cells, we found that DTx intoxication leads to cytolysis; indeed, release of 51Cr- and 75Se-labeled proteins could be detected within 7 h. However, little or no cell lysis was observed over a 20-50-h period when human U937 cells were exposed to cycloheximide, amino acid-deficient medium, or metabolic poisons even though protein synthesis was rapidly inhibited to levels observed with DTx. Likewise, investigations with human K562 cells revealed full resistance to the cytolytic action of DTx over a 50-h period despite a severe reduction in translation activity. These observations establish that inhibition of protein synthesis per se is not sufficient to provoke cell lysis. A characterization of DTx-induced cytolysis revealed a long lag period (6-7 h) which could be shortened considerably by a short exposure to low pH. NH4Cl and metabolic poisons blocked the cytolytic action of DTx, indicating that endocytic uptake of toxin is required for lytic activity. Surprisingly, DTx also induced extensive internucleosomal degradation of cellular DNA, a characteristic feature of apoptosis or programmed cell death. DNA-fragmentation preceded cell lysis and did not occur in DTx-treated K562 cells or in U937 cells that were treated with the other protein synthesis inhibitors. From these observations, we conclude that DTx-mediated cytolysis is not a simple consequence of translation inhibition and that internucleosomal DNA fragmentation is a newly identified and relatively early step in the cytolytic pathway of DTx.

Cell Line↗
PubMed1989

The in vivo depletion of V beta 17a+ T cells results in the inhibition of reticulum cell sarcoma growth in SJL/J mice. Evidence for the use of anticlonotypic antibody therapy in the control of malignancy.

Previous findings revealed that reticulum cell sarcoma (RCS) of SJL/J mice growth and survival depended on its ability to stimulate a potent host T cell response, by the means of a tumor-associated class II MHC molecule with IE-like specificities. Previously we presented evidence that the V beta 17a TCR+ clonotype of T cell was the predominant T cell involved in the host response to the tumor. We undertook our study to examine whether the depletion of the V beta 17a+ T cells, by the use of the anticlonotypic antibody, KJ23a, resulted in the inhibition of RCS tumor growth in vivo. We present evidence herein that supports this hypothesis. KJ23a-treated mice exhibited a complete reduction in T cells bearing the V beta 17a TCR. These mice exhibited a dramatic reduction in the in vitro proliferative response to RCS. Furthermore, the pretreatment of SJL/J mice with KJ23a mAb resulted in the complete loss in their ability to harbor RCS tumor. When tumor-bearing mice were treated with a single inoculum of KJ23a mAb within the first 7 days after the passage of tumor, the mice showed long term survival with diminishing tumor burden. These results demonstrated that the V beta 17a clonotype of T cells is required for the growth and maintenance of RCS tumor. Within the first 6 wk after tumor inoculation KJ23a-treated mice were capable of transferring tumor to naive syngeneic recipient mice despite the obvious lack of tumor growth in the treated donor animal. These results suggested that RCS tumors in the absence of V beta 17a+ T cells can persist for up to 6 wk in a state of "tumor dormancy." The predominant usage of the V beta 17a gene in RCS-specific T cells suggests that these T cells play an important role in the pathogenesis of RCS tumor. Furthermore, the positive therapeutic course taken by tumor-bearing mice upon the treatment with KJ23a mAb, demonstrates the enormous potential in anticlonotypic antibody therapy in the treatment of T cell-dependent tumors and diseases.

Animals↗
PubMed1989

Cytotoxic and cytostatic effects of the streptococcal preparation OK-432 and its subcellular fractions on human ovarian tumor cells.

Previous studies have indicated that OK-432 is a potent biologic response modifier (BRM) and that it augments immune responses to tumor cells. We studied the direct effect of OK-432 on tumor cells. Established and freshly derived human ovarian carcinoma lines were examined for their susceptibility to OK-432 or its subcellular fractions in direct cytotoxicity, cytostatic activity, and inhibition of metabolic activity. OK-432 was cytotoxic to 13 of 15 freshly derived ovarian carcinoma lines in a 24-hour chromium-51 (51Cr) release assay. The optimal effect was noticed at OK-432 concentrations between 0.1 and 1.0 Klinishe Einhert (KE) per milliliter. The cytostatic effect on two established lines and one fresh line correlated with the cytotoxic activity. In all three lines, however, the metabolic activities (DNA, RNA, and protein synthesis) were inhibited by OK-432, suggesting that cell lysis by OK-432 may not be directly correlated with the inhibition of metabolic activities. Several subcellular fractions were derived from OK-432 and only the cytoplasmic and protoplast membrane fractions showed cytotoxic activity against the OK-432-sensitive tumor cell lines, although the cytotoxicity obtained was greatly less than the whole microorganism OK-432. The direct binding of 14C-OK-432 to tumor cells was examined. Binding took place rapidly after 1 hour of incubation and reached a maximum activity at 37 degrees C. Binding in all three lines ranged between 1.7 and 2.7 pg/cell. These results demonstrate the direct cytotoxic effect of OK-432 and some subcellular fractions on human ovarian carcinoma lines. These results also show that the BRM OK-432 may exert its effect by both potentiating the antitumor response and directly inhibiting tumor cell growth.

Biological Products↗
PubMed1989

Calcium-independent pathway of tumor necrosis factor-mediated lysis of target cells.

The role of Ca2+ in cell-mediated cytotoxicity has been the subject of many investigations and both Ca2+-dependent and -independent pathways have been reported. TNF was suggested to play a role in NK and macrophage cell-mediated cytotoxicity. We assumed that its role in target cell lysis might take place by a Ca2+-independent mechanism. This hypothesis was investigated in assays of rTNF-mediated lysis of tumor target cells. Extracellular Ca2+ depletion by the calcium chelator EGTA (2 mM and 5 mM) and blocking of intracellular Ca2+ mobilization by 8-(diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride did not inhibit TNF-mediated tumor cell lysis. Furthermore, blocking of Ca2+ influx in the presence of the Ca2+ channel blocker Verapamil did not inhibit TNF-mediated tumor cell lysis. Previous reports showed that lysis of sensitive tumor cells by TNF is preceded by binding of TNF to TNF receptors, internalization, and DNA degradation. These events were tested in the absence of Ca2+. Treatment with Ca2+ inhibitors did not affect binding of 125I-TNF to target cells. Also TNF induced the fragmentation of cellular DNA in target cells without extracellular or intracellular Ca2+. These findings demonstrate that the mechanism of TNF-mediated tumor cell lysis does not depend on intracellular or extracellular Ca2+ and that events associated with target cell lysis can also function in the absence of Ca2+. Thus, our findings support the contention of a Ca2+-independent lytic pathway in which secreted or membrane-bound TNF may interact with the target cells and ultimately result in DNA degradation and target cell lysis.

Calcium↗
PubMed1989

Liposomes can function as targets for natural killer cytotoxic factor but not for tumor necrosis factor.

NK cells exert their lytic action through the release of NK cytotoxic factors (NKCF) after stimulation by the bound target cell. NKCF may be related to granule-derived perforin/cytolysin on one hand and to the pleiotropic cytokine TNF on the other hand. In the present study, we show that NKCF can also lyse artificial lipid vesicles, as had been reported previously for cytotoxic granules and cytolysin. The lysis of large unilamellar vesicles was monitored by measuring the release of the encapsulated fluorescent dye carboxyfluorescein. NKCF-induced lysis was only observed with liposomes composed of a complex mixture of lipids including acidic phospholipids. No lysis could be demonstrated if the liposomes contained phosphatidylcholine as the only phospholipid, suggesting some kind of lipid specificity for the action of NKCF. A remarkable finding was that neither recombinant nor natural TNF were able to lyse large unilamellar vesicles, irrespective of their lipid composition, indicating different ways of interaction of NKCF and TNF with artificial (and presumably also biological) membranes.

Adsorption↗
PubMed1989

A spontaneous sarcoma dependent on host tumor-specific immune lymphocytes.

The immune surveillance theory postulates that spontaneous tumors are normally rejected by the immune system and appear only when they override host-immune recognition and rejection mechanisms. The present mini-review describes a spontaneous tumor system, the reticulum cell sarcomas (RCS) in SJL/J mice, that is dependent on host tumor-specific immune lymphocytes for growth. This continuous tumor-specific response results in tumor progression and death of the host. This tumor system contradicts the basic concept of immune surveillance. We propose as an explanation that some highly antigenic tumors, like the RCS, may have evolved in a non-autonomous fashion but, nevertheless, have lost regulatory controls of cell proliferation. In the RCS system, the tumor expresses Class II MHC I-E like specificities that are not expressed on the host cells and which selectively stimulate a subpopulation of I-E specific T cells, the V beta 17 a+ clonotype, leading to their expansion and continuous nurturing of the tumor via secreted lymphokines. This neoantigenic stimulation bypasses the tumor regulatory response that might have resulted if the tumor had not expressed neoantigens. Furthermore, passive administration of anti-clonotypic antibody to tumor-bearing mice results in tumor regression and long-term survival through removal of the tumor reactive T cells. Thus, in this tumor system, immunosuppressive treatments are the prescription for tumor rejection.

Animals↗
PubMed1989

Effect of platelet-activating factor on monocyte activation and production of tumor necrosis factor.

The effect of platelet-activating factor (PAF) or human peripheral-blood-derived monocytes (PBM) was examined. The addition of PAF to monocyte cultures did not activate the cells to mediate cytotoxicity activity against 51Cr-labeled target cells. Furthermore, supernatants derived from the treated cultures were not cytotoxic. However, these supernatants contained tumor necrosis factor (TNF) when assayed by a sensitive radioimmunoassay. Further kinetic studies indicated that cytotoxic supernatant is detected at 2-4 h following PAF treatment but not overnight treatment, suggesting, perhaps, the presence of inhibitors interfering with the cytotoxic activity. Cells pretreated with PAF responded poorly to a second stimulation with phorbol myristate acetate whereas a secondary response was seen with cells pretreated with interferon-gamma. These results suggest that PAF is involved in regulating cytokine production by monocytes and thus plays a role in the immune response to foreign antigens.

Cell Line↗
PubMed1988

The SJL/J T cell response to both spontaneous and transplantable syngeneic reticulum cell sarcoma is mediated predominantly by the V beta 17a+ T cell clonotype.

Previous studies have revealed that the reticulum cell sarcoma (RCS) of SJL/J (H-2s, IE-) mice express an "IE-like" stimulatory tumor-associated antigen, the expression of which is requisite for stimulating host T cells necessary for tumor growth. Herein, we present evidence that the predominant T cells raised in the syngeneic response to both spontaneous and transplantable RCS tumors are of the V beta 17a TCR clonotype. The V beta 17a+ clonotype of T cells has been shown to interact with IE allogeneic specificities. We demonstrate that all four characterized RCS-specific T cell hybridomas stained positively for the anti-V beta 17a mAb, KJ23a. Additionally, KJ23a, when added to cocultures of the T cell hybridomas and RCS tumors, inhibited the release of IL-2 by the hybridomas. Further, KJ23a was shown to markedly inhibit the proliferation of SJL/J T cells when cocultured with either spontaneous or transplantable RCS tumor cells. When analyzed by flow cytometry, the T cell blast population raised in response to both spontaneous and transplantable RCS were greater than 80% KJ23a+. These T cells were brightly stained by the anti-CD4 mAb, Gk1.5, and, therefore, represent class II-responsive T cells. In corroboration of the in vitro data, T cells derived from mesenteric lymph nodes of RCS tumor-bearing mice had likewise undergone a similar expansion of V beta 17a+, CD4+ T cells. Together, these results indicate that KJ23a+ T cells play an important and predominant role in the response of SJL/J mice to spontaneous RCS tumors and provide further suggestive evidence that the stimulatory antigen(s) on the RCS tumor is IE or an "IE-like" molecule. Significantly, the important role V beta 17a+ T cells play in the response to RCS suggests a potential therapeutic role for KJ23a mAb in the intervention and prevention of RCS tumors in SJL/J mice.

Animals↗
PubMed1988

Capacity of tumor necrosis factor to bind and penetrate membranes is pH-dependent.

Studies with human U937 cells as targets established that a 15-min exposure to rTNF at pH 5.3 caused a significant increase in TNF-mediated cytolysis when compared to cells exposed to TNF at pH 7.4. A detailed examination of TNF-membrane interactions revealed that although TNF bound avidly to model membrane targets, no damage was generated under any condition tested. Binding of TNF, monitored with 125I-labeled as well as unlabeled protein, was enhanced at low pH. In the pH range tested (i.e., 4 to 8), target membrane permeability actually decreased in the presence of TNF. This membrane stabilization may be a consequence of TNF insertion into the target bilayer, a process we detected through use of an intramembranous photolabeling assay; interestingly, the efficiency of TNF insertion into membranes increased dramatically with decreasing pH. We conclude that native TNF does not cause pore formation directly and that its ability to induce cell lysis, as monitored by 51Cr release, is a consequence of some as yet obscure signaling event or intracellular activity. Parallel studies were carried out with diphtheria toxin, a protein with a more thoroughly characterized pH-dependent intoxification pathway. This toxin displayed acid-enhanced activities with both biologic and artificial targets.

Bacterial Toxins↗
PubMed1988

Spontaneous cytotoxicity and tumor necrosis factor production by peripheral blood monocytes from AIDS patients.

Peripheral blood monocytes (PBM) from AIDS patients have exhibited defects in some but not all of the immune functions yet tested. This study has examined the capacity of AIDS PBM to lyse tumor target cells as well as their ability to secrete TNF. Untreated PBM from AIDS patients were significantly cytotoxic to U937 target cells and responded to IFN-gamma pretreatment with augmented cytotoxicity. Both the spontaneous and IFN-gamma-stimulated cytotoxic activity was significantly (p less than 0.01) higher than that observed with normal PBM. The cytotoxic activity depended on the E:T ratio used and was higher in AIDS PBM at all ratios tested (10:1 to 40:1). Because TNF has been implicated in macrophage cell-mediated cytotoxicity, we examined whether the elevated cytotoxic activity of AIDS PBM was associated with an increase in TNF production. Supernatants from PBM cultured overnight with or without IFN-gamma were tested in a bioassay measuring cytotoxicity against U937 target cells as well as in an RIA specific for TNF. Supernatants derived from either unstimulated or IFN-gamma-treated AIDS PBM exhibited significantly higher levels of cytotoxicity than supernatants from normal macrophages. Both normal and AIDS PBM produced higher levels of cytotoxic factors in response to IFN-gamma. As determined by the RIA, AIDS PBM spontaneously released high levels of TNF whereas little TNF was produced by normal PBM. Treatment with IFN-gamma augmented the level of TNF production in both AIDS and normal PBM. These results demonstrate that PBM from AIDS patients have undergone in vivo activation as manifested by both cytotoxicity against tumor target cells and production of TNF. Target cell lysis by both AIDS PBM and their supernatants was inhibited by monoclonal anti-rTNF, suggesting that the increase in PBM cell-mediated cytotoxicity was caused by an increase in TNF production. The significance of these findings in the pathogenesis of the disease is discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Sensitivity of fresh and cultured ovarian tumor cells to tumor necrosis factor, interferon-alpha 2, and OK-432.

The in vitro sensitivity to rTNF, rIFN-alpha 2, and OK-432 of 11 freshly derived human ovarian tumors and 2 established tumor cell lines was examined in a cytotoxic assay using the 51 Cr release test. Nine fresh lines were sensitive to rTNF, 8 to OK-432, and only 2 were sensitive to rIFN-alpha 2. Cytotoxicity by rIFN-alpha 2 was of lesser magnitude than the cytotoxicity mediated by rTNF or OK-432. The time of exposure and the concentration of BRM required for maximal cytotoxicity varied from line to line. Two fresh tumor cell lines and 1 established cell line (PA-1) were sensitive to all 3 BRMs, while 2 other FOCs and 1 cell line (SKOV-3) were resistant to all BRMs. The remaining FOC showed an intermediate degree of sensitivity. These results demonstrate the existence of heterogeneity of ovarian carcinoma tumor cell lines to lysis by BRMs. Among the FOCs, the 2 endometrioid carcinomas tested were highly sensitive to rTNF, whereas the serous carcinomas were more sensitive to OK-432. Low grade tumors were more sensitive to BRM than high grade tumors, and tumor extension did not correlate with sensitivity to the BRM. When tumor targets were exposed to more than 1 BRM added either simultaneously or sequentially, the net cytotoxic effect achieved was usually inferior to the sum cytotoxicity obtained by each BRM alone. Furthermore, rTNF and OK-432 were cytostatic to most ovarian tumor cell lines examined. The results of this study demonstrate that certain BRMs exert a direct effect on fresh ovarian tumor cells independently of host factors. These findings suggest that in vitro screening of a patient's tumor cells for sensitivity to a particular BRM prior to therapy could be beneficial for the proper identification of patients most likely to benefit from the treatment.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1988

Antibody-dependent cellular cytotoxicity (ADCC)-mediated destruction of human immunodeficiency virus (HIV)-coated CD4+ T lymphocytes by acquired immunodeficiency syndrome (AIDS) effector cells.

The acquired immunodeficiency syndrome (AIDS) is defined in clinical terms by the development of Kaposi's sarcoma and/or severe opportunistic infections in persons without predisposing conditions. A hallmark of the syndrome has been a decrease in the number of CD4+ T helper cells. The reduction in the frequency of the CD4+ lymphocytes has been postulated to be primarily the result of human immunodeficiency virus (HIV) tropism and cytophathogenicity for the T-cell subset. Yet only a small percentage of cells in actually infected with HIV. Recently, we provided evidence indicating that AIDS patients' natural killer cells can mediate normal levels of antibody-dependent cellular cytotoxicity (ADCC) despite exhibiting a defect in natural killer (NK) effector function (J Immunol 139:55, 1987). This finding prompted us to investigate whether AIDS patients' effector cells could mediate ADCC against circulating CD4+ T cells infected with or expressing HIV antigen. The findings reported herein demonstrate that AIDS effector cells can mediate lysis of CEM (CD4+ T-cell line) coated with HIV protein in the presence of HIV-specific antibody. Lysis was specific, as non-HIV-coated CEM or the addition of HIV-negative serum resulted in no lysis. We then examined HIV-coated peripheral blood-derived CD4+ T lymphocytes as targets in ADCC. We demonstrate that in the presence of HIV-specific antibody, HIV-coated CD4+ T lymphocytes serve as targets for ADCC by AIDS effector cells. The lytic activity obtained with AIDS effector cells was comparable to that obtained with normal effector cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1987

Effect of altered membrane structure on NK cell-mediated cytotoxicity. III. Decreased susceptibility to natural killer cytotoxic factor (NKCF) and suppression of NKCF release by membrane rigidification.

We have shown recently that alteration of the membrane fluidity of either effector or target cells results in significant and selective inhibition of NK cell-mediated cytotoxicity (NK CMC). However, the localization of the defective stage in the NK lytic pathway is not known. In the present study, we show that rigidification of the NK-sensitive U937 target cell membrane by lipid modulation reduces its sensitivity to lysis by NK cytotoxic factor (NKCF). This resistance was not due to loss of NKCF binding sites on the target cell because target cells with rigid membranes absorbed more NKCF than control cells. The enhanced ability to absorb NKCF by membrane modification was supported by data showing that NK-resistant Raji cells lacking NKCF-binding sites absorb NKCF after lipid modification. Furthermore, consistent with the lipophilic nature of NKCF, synthetic lipid vesicles absorb NKCF. In contrast to membrane rigidification, membrane fluidization of the target cell did not change the target cell properties. Rigidification of the NK effector cell membrane abrogates it ability to secrete active NKCF when stimulated by target cells or by mitogens. Membrane fluidization of the NK effector cells did not inhibit their ability to release NKCF. The results of these studies demonstrate that inhibition of NK CMC by rigidification of the target cell membrane results in cells that are inhibited in processing bound NKCF to lysis. Inhibition of NK CMC by rigidification of the NK effector cell results in defective trigger for activation of the NKCF release mechanism.

Adult↗