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B Bonavida

Publications and source records attributed to B Bonavida.

At least 73 records · Page 4Linked to original sources
PubMed1995

Target-induced anergy of natural killer cytotoxic function is restricted to the NK-target conjugate subset.

This study examined the characteristics of functional anergy of natural killer cells (NK) following their interaction with target cells. Purified NK cells were cocultured with K562 for 15 min or 4 hr to allow for binding of targets to NK cells. The resulting NK-target conjugates were then dissociated by EDTA, and the unbound NK cells were separated from the targets by flow cytometry and cell sorting. Compared to untreated NK cells, the K562-dissociated NK cells were inhibited for cytotoxic function as assessed by the 51Cr release assay and by the single killer frequency assay and also responded poorly following activation by IL-2 or IFN-alpha. The inactivated NK cells had a diminished ability to reform conjugates with the target cells. Following cell sorting of the NK subsets, the conjugate subset had the least cytotoxic activity when compared to both the free NK subset or the unfractionated NK population. The IL-2 response observed with the unfractionated anergic NK cells was found to be due to the activation of the NK free cell subset while the conjugate subset was poorly responsive to IL-2. The cell surface CD16, CD2, and CD56 antigen expression was downmodulated in the conjugate subset but not in the free cells. However, the CD69 surface expression was significantly upregulated on the surface of the NK conjugate subset and was potentiated following treatment with IFN-alpha and IL-2. These results demonstrate that target-mediated anergy of NK cells is restricted to the NK-target conjugate subset while sparing the remaining free cell subset. Further, the findings demonstrate that the anergic NK cells express the phenotype CD16dimCD2dimCD56dimCD69brightCD11bbright.

Cell Adhesion↗
PubMed1995

Enhanced susceptibility of c-myc antisense oligonucleotide-treated human renal cell carcinoma cells to lysis by peripheral blood lymphocytes.

C-myc oncogene expression has been implicated in the poor prognosis of human renal cell carcinoma (RCC), and these tumor cells are resistant to cytotoxic effector cells. We hypothesized that the resistance of RCC cells to lysis by cytotoxic effector lymphocytes might be regulated by c-myc expression. The present study tested this hypothesis by examining the effect of c-myc antisense oligonucleotide treatment on the susceptibility of RCC to lysis by cytotoxic lymphocytes. The Caki-1 human RCC cell line constitutively expresses c-myc mRNA, and treatment with c-myc antisense oligonucleotide resulted in a significant inhibition of the expression of c-myc mRNA and enhanced susceptibility to lysis by peripheral blood lymphocytes (PBL). The enhanced susceptibility to lysis was observed by PBL derived from both normal donors and patients with RCC. The susceptibility of c-myc antisense oligonucleotide-treated Caki-1 cells to lysis by lymphokine-activated killer (LAK) cells, natural killer (NK) cells, and tumor-infiltrating lymphocytes (TIL) was also enhanced. Furthermore, enhanced susceptibility was also seen when freshly isolated autologous tumor cells were used as target cells. The mechanism of the enhanced susceptibility of c-myc antisense oligonucleotide-treated Caki-1 cells to lysis was examined. No effect was observed on the expression of major histocompatibility complex (MHC) class I and MHC class II on the tumor cells. However, there was a modest increase in the frequency of effector-target binding. Further, c-myc antisense oligonucleotide-treated Caki-1 cells were more susceptible to lysis by tumor necrosis factor-alpha (TNF-alpha). The findings of this study demonstrate that c-myc antisense oligonucleotide directly affects established RCC cells and freshly isolated RCC cells by rendering them more susceptible to lysis by PBL, LAK cells, NK cells, and T lymphocytes. The enhanced susceptibility may be due in part to the enhanced sensitivity to TNF-alpha and to the augmentation of PBL binding to tumor cells. The possible clinical implications of these findings are discussed.

Adolescent↗
PubMed1995

Lysis of uninfected HIV-1 gp120-coated peripheral blood-derived T lymphocytes by monocyte-mediated antibody-dependent cellular cytotoxicity.

Previous reports from our laboratory have demonstrated that peripheral blood monocytes (PBM) from HIV-1 infected individuals are de novo activated and are cytotoxic in vitro. Significant monocyte-antibody-dependent cellular cytotoxicity (ADCC) was obtained against HIV-1 inactivated CD4+ CEM target cells coated with HIV-1 in the presence of autologous seropositive serum. Based on these findings, we hypothesized that in HIV-seropositive individuals the monocytes may play an important role in vivo in the autodestruction of non-infected CD4+ T lymphocytes. The present study was designed to test this hypothesis. Monocytes from normal donors activated with M-CSF lysed CD4+ T cells (CEM) coated with gp120 sensitized by plasma from asymptomatic HIV-1+ individuals in a 8 h 51Cr release assay. ADCC cytotoxic activity varied from one individual to another and was a function of the dilution of the individual seropositive plasma used. We then used circulating CD3+ T lymphocytes as targets for ADCC following treatment with actinomycin D to facilitate the release of radioactive 51Cr. Like CEM, ADCC was obtained with CD3+ T cells coated with gp120 in the presence of HIV seropositive plasma and monocytes. Lysis was specific as T cells that were not coated with gp120 were not destroyed. These findings demonstrate that activated peripheral blood derived monocytes can destroy non-infected gp120-coated circulating T lymphocytes by an ADCC-mediated mechanism. Thus, these findings suggest that ADCC may be one mechanism operating in vivo for the destruction of non-infected CD4+ T lymphocytes.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1994

Enhancement of sensitivity of urinary bladder tumor cells to cisplatin by c-myc antisense oligonucleotide.

BACKGROUND: Tumor cells have different degrees of sensitivity and resistance to anticancer agents. The acquisition of drug resistance is a major concern in cancer treatment. Because the c-myc oncogene has been implicated in the poor prognosis of some human tumors including urinary bladder tumor (UBT), the resistance of such tumors to anticancer drugs may correlate with c-myc expression. The present study tested this hypothesis by examining the effect of c-myc antisense oligonucleotide treatment on the sensitivity of human UBT cells to anticancer chemotherapeutic agents. METHODS: Cytotoxicity determined by a 1-day microculture tetrazolium dye assay. C-myc mRNA was examined by Northern blot analysis. RESULTS: The T24 human UBT cell line constitutively expresses c-myc mRNA. Treatment of T24 cells with the c-myc antisense oligonucleotide resulted in a significant inhibition of the expression of c-myc mRNA. Treatment of T24 cells with the c-myc antisense oligonucleotide in combination with mitomycin C, Adriamycin, or 5-fluorouracil (5-FU) did not overcome their resistance to these anticancer chemotherapeutic agents. However, combination treatment with the c-myc antisense oligonucleotide and CDDP resulted in a synergistic cytotoxic effect on T24 cells and two freshly derived UBT cells. Further, treatment of CDDP-resistant T24 cells (T24/CDDP) with c-myc antisense oligonucleotide and CDDP reversed the resistance. Pretreatment of T24 cells with either agent and then treatment with the second agent resulted in the same cytotoxic activity as achieved in the presence of the two agents. The combination of c-myc antisense oligonucleotide and carboplatin also resulted in a synergistic cytotoxic effect on T24 cells, and the combination of c-myc antisense oligonucleotide and trans-diamminedichloro-platinum resulted in an additive cytotoxic effect. Incubation of T24 or T24/CDDP cells with the c-myc antisense oligonucleotide increased the intracellular accumulation of CDDP, but not the accumulation of 5-FU. CONCLUSIONS: This study demonstrates that combination treatment with c-myc antisense oligonucleotide and CDDP can overcome the CDDP-resistance of UBT cells and that the increased intracellular accumulation of CDDP by c-myc antisense oligonucleotide may play a role in the enhanced cytotoxicity obtained. The synergistic effect obtained with established UBT cells and freshly isolated UBT cells suggests that combination treatment with c-myc antisense oligonucleotide and CDDP may have clinical application in the therapy of CDDP-resistant UBT.

Antineoplastic Agents↗
PubMed1994

Activation of the human immature natural killer cell subset by IL-12 and its regulation by endogenous TNF-alpha and IFN-gamma secretion.

Interleukin-12 (IL-12) is a newly described cytokine that can activate NK cell cytotoxic function. The present study investigated the activation pathway of human peripheral blood-derived immature NK cells by IL-12 and its comparison to activation by interleukin-2 (IL-2). Immature NK cells were prepared by flow cytometry cell sorting techniques whereby the nonbinding Free NK subset was separated from the NK target conjugate subpopulation. Coculture of Free cells with IL-12 overnight resulted in enhanced cytotoxicity and recruitment of cytotoxic Killer cells. The IL-12-mediated activation of cytotoxicity was dependent on endogenous TNF-alpha secretion and was suppressed by endogenous (interferon-gamma (IFN-gamma) secretion. However, IL-2-mediated activation was inhibited by anti-TNF-alpha antibody, but was not affected by endogenous IFN-gamma secretion. There was an upregulation of the expression of CD69 and CD25 surface antigens by IL-12-treated cells and this upregulation was diminished in the presence of anti-TNF-alpha antibody. IL-12 also upregulated the expression of the 75-kDa TNF receptor (TNF-R p75) and the upregulation was inhibited by anti-IFN-gamma antibody. The 55-kDa TNF receptor (TNF-R p55), however, was not affected by IL-12, but in the presence of anti-IFN-gamma antibody, its expression was enhanced. Thus, these results suggest that IFN-gamma selectively upregulates the expression of TNF-R p75 by IL-12 but inhibits the expression of TNF-R p55 by IL-12. Unlike IL-2, IL-12, does not stimulate the proliferation of Free cells. Furthermore, unlike IL-2, IL-12 does not stimulate the secretion of TNF-alpha by Free cells, but significantly stimulates IFN-gamma secretion. These findings demonstrate that IL-12 share some, but not all, properties of IL-2 in the activation pathway of immature NK Free cells. Furthermore, the pathway of activation of Free cells by IL-12 is under the regulation of both endogenous TNF-alpha and IFN-gamma secretion.

Antigens, CD↗
PubMed1994

Cytotoxic effect of diphtheria toxin used alone or in combination with other agents on human renal cell carcinoma cell lines.

Treatment of renal cell carcinoma (RCC) by conventional chemotherapy and immunotherapy has resulted in minimal remissions. Alternative forms of therapy are therefore being sought. The present study investigated the sensitivity of RCC cell lines to several toxins used alone and in combination with other agents. RCC lines were relatively sensitive to the direct cytotoxic effect of diphtheria toxin (DTX), Pseudomonas aeruginosa exotoxin A (PEA) and ricin. Furthermore, DTX in combination with tumor necrosis factor-alpha (TNF-alpha) resulted in synergistic cytotoxic activity. The mechanism of synergy was examined. A possible mechanism of resistance to TNF-alpha in tumor cells is the expression of TNF-alpha mRNA or protein. R11 cells did not constitutively express mRNA for TNF-alpha, however, treatment of R11 cells with TNF-alpha induced the expression of TNF-alpha mRNA. When DTX was used in combination with TNF-alpha, the level of TNF-alpha mRNA induced by TNF-alpha was markedly reduced. These studies suggest that DTX in combination with TNF-alpha can overcome the resistance of RCC lines and that the marked downregulation of TNF-alpha mRNA by DTX may play a role in the enhanced cytotoxicity seen with the combination of DTX and TNF-alpha. Furthermore, the combination treatment might also potentiate the antitumor host responses. The implications of these findings in clinical therapy are discussed.

ADP Ribose Transferases↗
PubMed1994

Inhibition of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) secretion but not IL-6 from activated human peripheral blood monocytes by a new synthetic demethylpodophyllotoxin derivative.

A newly synthesized demethylpodophyllotoxin derivative, 4-O-butanoyl-4'-demethylpodophyllotoxin (BDPT) or BN58705, has recently been shown to exert a potent cytotoxic activity in vitro against a variety of drug-resistant human tumor cell lines. The effect of this agent on effector cells of the immune system, however, has not been examined. The present study investigated the effect of BDPT on the response of activated human peripheral blood derived monocytes (PBM) to secrete cytokines. Activation of PBM overnight with LPS, IFN-gamma, or PMA resulted in secretion into the supernatant of TNF-alpha, IL-1 beta, IL-6, and IL-8 as assessed by ELISA. The addition of BDPT to the stimulated cultures resulted in significant inhibition of TNF-alpha and IL-1 beta secretion, whereas the secretion of IL-6 and IL-8 was not affected. The selective inhibition of TNF-alpha and IL-1 beta secretion by BDPT-treated PBM was observed with all three stimuli tested. The inhibitory effect mediated by BDPT was concentration dependent and was optimal at 6-20 microM. Time kinetic analysis indicated that the inhibition of secretion was rapid and detected as soon as 2 hr following stimulation of the PBM and lasted for as long as 24 hr. A comparison was made between BDPT and pentoxyfilline, a xanthine-derived phosphodisterase inhibitor that was reported to inhibit TNF-alpha and IL-1 beta secretion by PBM. Both BDPT and PTX showed similar time kinetics and patterns of inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1994

Pentoxifylline suppresses interleukin-2-mediated activation of immature human natural killer cells by inhibiting endogenous tumor necrosis factor-alpha secretion.

We recently reported that immature human peripheral blood-derived natural killer (NK) cells, the free NK subset, can be activated by interleukin-2 (IL-2) to become killer cells and to undergo proliferation. Activation by IL-2 is dependent on endogenous secretion of tumor necrosis factor-alpha (TNF-alpha) by the free cells. Because pentoxifylline (PTX) inhibits TNF-alpha synthesis and secretion in monocytes, we hypothesized that PTX may also inhibit TNF-alpha secretion by NK cells and thus would inhibit IL-2-mediated activation of free cells. The free NK cells were separated from purified NK cells by flow cytometry and cell sorting of non-target binding cells. IL-2-mediated secretion of TNF-alpha by the free cells was inhibited by PTX. In the presence of PTX, IL-2-mediated activation of free cells into cytotoxic function, proliferation, and recruitment of binder and killer cells was markedly inhibited. Also, PTX inhibited IL-2-triggered upregulation of the expression of CD69, CD25, ICAM-1, and p75TNF-R on the cell surface. These findings demonstrate that PTX has a marked suppression on IL-2-mediated activation of immature free NK cells and that the suppression is due, in large part, to PTX-mediated inhibition of endogenous TNF-alpha secretion. The implication of these findings in the clinical use of PTX for therapy is discussed.

Antigens, Surface↗
PubMed1994

Overcoming TNF-alpha and drug resistance of human renal cell carcinoma cells by treatment with pentoxifylline in combination with TNF-alpha or drugs: the role of TNF-alpha mRNA downregulation in tumor cell sensitization.

Previous studies have demonstrated that one of the possible mechanisms responsible for the resistance of tumor cells to tumor necrosis factor-alpha (TNF-alpha) is the expression of TNF-alpha mRNA and/or protein. Pentoxifylline (PTX) suppressed TNF-alpha gene transcription and downregulates the expression of TNF-alpha mRNA and the secretion of TNF-alpha protein in macrophages and monocytes. This study investigates whether PTX downregulates the expression of TNF-alpha mRNA and/or protein in renal cell carcinoma (RCC) cells and whether PTX enhances the sensitivity of TNF-alpha-resistant RCC cells to TNF-alpha. Further, we explored whether PTX enhances the sensitivity of RCC cells to agents other than TNF-alpha by downregulation of the expression of TNF-alpha mRNA and protein. The R4 human RCC cell line constitutively expressed TNF-alpha mRNA and protein and was resistant to TNF-alpha. When R4 cells were incubated with PTX, the level of TNF-alpha mRNA and protein was markedly reduced. Pentoxifylline and TNF-alpha together overcame the resistance of R4 cells to TNF-alpha. The R11 human RCC cell line did not constitutively express TNF-alpha mRNA or protein, and was resistant to TNF-alpha. The expression of TNF-alpha mRNA in R11 cells, but not the production of TNF-alpha protein, was induced by TNF-alpha. When PTX was used in combination with TNF-alpha, the level of TNF-alpha mRNA induced by TNF-alpha was markedly reduced. The combination of PTX and TNF-alpha overcame the resistance of R11 cells to TNF-alpha. Pentoxifylline also enhanced the sensitivity of R4 cells to interferon-alpha. Pentoxifylline and anti-TNF-alpha monoclonal antibody augmented the sensitivity of R4 cells to cis-diamminedichloroplatinum (II) (CDDP). This study demonstrated that PTX, in combination with TNF-alpha, IFN-alpha or CDDP, overcame the drug resistance to RCC cells and that downregulation of TNF-alpha mRNA by PTX may be related to the cytotoxicity enhanced by the combination. The implications of these findings for clinical therapy are discussed.

Carcinoma, Renal Cell↗
PubMed1994

A comparative study of intravenous versus intralymphatic interleukin-2, with assessment of effects of interleukin-2 on both peripheral blood and thoracic-duct lymph.

Recombinant human interleukin-2 (IL-2) was administered by the intravenous (i.v.) or intralymphatic (i.l.) route to 14 patients with advanced malignancy. IL-2 was given in doses of 600,000 IU/kg or 1,050,000 IU/kg daily x 5. Thoracic duct (TD) catheters were placed, and both TD lymphocytes (TDL) and peripheral blood lymphocytes (PBL) were studied. Five of eight patients at the 600,000 IU/kg dose experienced grade III toxicity as did five of six patients at the 1,050,000 IU/kg dose. Two episodes of grade IV toxicity were seen at the higher dose. The i.l. and i.v. routes had a similar toxicity profile excepting lymphangitis/pedal infection, seen only with i.l. administration. One partial response was seen in a patient with renal cell carcinoma. Lymphopenia was seen early in therapy, with lymphocytosis by day 6. Lymphoid yield of the TD catheter fell early in therapy, then increased over baseline by the end of treatment. Intralymphatic administration resulted in a prolonged serum t1/2 and lower serum levels than did i.v. administration, but resulted in higher TD levels. Antibodies against IL-2 were ubiquitous but had no clear effects. Lymphocyte trafficking studies suggested that IL-2 affected lymphocyte redistribution to liver, spleen, bone marrow, and lymph nodes. NK activity and phenotype and LAK activity increased in response to IL-2, with no advantage for TDL. Tumor necrosis factor-alpha and gamma-interferon levels increased sporadically with treatment. The i.l. route offered no advantage over the i.v. route, and TDL offered no advantage over PBL.

Adult↗
PubMed1994

Qualitative and quantitative analysis of subpopulations of cytotoxic effector cells by flow cytometry.

The heterogeneous nature of cytotoxic effector cells presents a difficult obstacle to the study of developmental, biochemical and molecular events governing cytotoxic T lymphocytes (CTL) and natural killer (NK) cell biology. In previous studies, there were no available methods, other than the single cell assay or micromanipulation techniques that could distinguish between lytic and non-lytic cells present in purified populations or clones. Further, there were no available means to isolate these subsets for further investigation. The studies presented here describe a novel approach to identify and isolate cells based on their functional characteristics. Thus, non-lytic free and conjugate forming cells as well as killer cells could be identified, quantified, and further purified by flow cytometric cell sorting for further investigations. Studies of several properties of isolated NK subpopulations (free, non-lytic binders, and killers) are presented.

Animals↗
PubMed1993

Pivotal role of endogenous TNF-alpha in the IL-2-driven activation and proliferation of the functionally immature NK free subset.

Highly purified peripheral blood-derived NK cells can be separated into three functionally defined subpopulations, namely, non-target binding free cells, binders, and killers. The free cell subset is the least mature and was examined for its response to IL-2-mediated activation and the role of endogenous secretion of TNF-alpha in its maturation and differentiation. The findings demonstrate that endogenous TNF-alpha secretion is prerequisite for the initiation of IL-2-mediated activation of free cells into killer cells. The addition of IL-2 to free cells upregulated the surface expression of IL-2R (TAC), TNF-R (p75), CD69, and ICAM-1 antigens and also stimulated cell proliferation. Furthermore, the addition of IL-2 to free cells resulted in the induction of cytotoxic activity and stimulation of free cells to become binder and killer cells. All of these IL-2-mediated manifestations are shown to be downregulated by the addition of anti-TNF-alpha antibody. However, IL-2-mediated TNF-alpha secretion was not affected by the addition of anti-TNF-alpha antibody. The specificity of the anti-TNF-alpha antibody-mediated inhibition was corroborated by the failure of the antibody to inhibit interferon-alpha-mediated activation of free cells into killer cells. Most of the events associated with the inhibitory activity of anti-TNF-alpha antibody were mimicked by the addition of IL-4 to IL-2-treated free cells. These findings suggest that the IL-2-mediated maturation and differentiation of the immature free cells to become cytotoxic and proliferate are the result of a sequence of events that are initiated by the secretion of endogenous TNF-alpha.

Antibodies↗
PubMed1993

Overcoming cis-diamminedichloroplatinum (II) resistance of human ovarian tumor cells by combination treatment with cis-diamminedichloroplatinum (II) and tumor necrosis factor-alpha.

BACKGROUND: Previous studies have demonstrated that tumor cells have different degrees of sensitivity and resistance to various cytotoxic agents. The acquisition of drug resistance is a major concern in cancer treatment. The current study investigates the cytotoxic effect of cis-diamminedichloroplatinum (II) (CDDP) and tumor necrosis factor-alpha (TNF-alpha) used in combination on CDDP-resistant human ovarian tumor cell lines. METHODS: Cytotoxicity was determined by the microculture tetrazolium dye assay. Synergy was assessed by isobolographic analysis. TNF-mRNA was examined by Northern blot analysis. RESULTS: Treatment of the CDDP-resistant C30 cells with CDDP and TNF-alpha overcame the resistance of C30 cells to CDDP or TNF-alpha. In addition, the combination of CDDP and TNF-alpha resulted in a synergistic effect on the C30-resistant line, the CDDP-sensitive parental cell line A2780, and two freshly derived ovarian carcinoma cell cultures. Treatment of C30 cells with CDDP followed by TNF-alpha showed a synergistic effect, whereas treatment with TNF-alpha followed by CDDP demonstrated a less cytotoxic effect. A possible mechanism of resistance to TNF-alpha in tumor cells is the induction of TNF-alpha mRNA and protein. C30 cells do not produce mRNA constitutively for TNF-alpha; however, treatment of C30 cells with TNF-alpha induces the expression of TNF-alpha mRNA. When CDDP was used in combination with TNF-alpha, the level of TNF-alpha mRNA induced by TNF-alpha was reduced significantly. CONCLUSIONS: This study shows that the combination of CDDP and TNF-alpha can overcome the CDDP resistance of tumor cells and that downregulation of TNF-alpha mRNA by CDDP may play a role in the enhanced cytotoxicity seen with the combination of CDDP and TNF-alpha. The synergistic effect obtained with established ovarian tumor cell lines and in short-term cultures of freshly isolated ovarian tumors suggests that combination treatment with TNF-alpha and CDDP may have clinical applications in the treatment of drug-resistant tumors.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1993

Overcoming tumor necrosis factor and drug resistance of human tumor cell lines by combination treatment with anti-Fas antibody and drugs or toxins.

Monoclonal mouse anti-Fas antibody is directed against Fas antigen, a M(r) 36,000 encoded polypeptide that belongs to the family of cell surface proteins which includes nerve growth factor receptor, tumor necrosis factor (TNF) receptors, B-cell antigen CD40, and T-cell antigens OX40. Anti-Fas antibody mimics TNF-alpha in its cytolytic activity but not in other TNF-alpha-mediated activities. Thus, we examined if anti-Fas antibody synergizes in cytotoxicity with toxins and drugs. The present studies demonstrate that anti-Fas antibody in combination with diphtheria toxin (DTX), Adriamycin, or cis-platinum results in enhanced cytotoxicity and synergy and also overrides resistance to TNF, drugs, or toxins when tested against a battery of human tumor cell lines. Synergy with anti-Fas and DTX requires that DTX is enzymatically active, since inhibitors of DTX-mediated protein synthesis inhibition resulted in loss of synergy. When the plant toxin ricin was used, there was no synergy with anti-Fas antibody but rather an additive effect. The synergy was not obtained in a TNF receptor-negative line but was achieved with other anti-Fas-resistant lines. Cell lines resistant to either Adriamycin or cis-platinum were rendered sensitive by the combination of drug and anti-Fas antibody. Further, combination treatment of anti-Fas and Adriamycin overcame resistance of the gp 170-expressing, multidrug-resistant MDR ovarian line. In all cases, cytotoxicity was augmented by pretreatment of target cells with gamma-interferon which upregulates Fas antigen expression. These results show that anti-Fas antibody can synergize in cytotoxicity with toxins and chemotherapeutic drugs, and combination treatment can reverse resistance to TNF, toxins, and/or drugs.

Antibodies, Monoclonal↗
PubMed1993

Enhanced susceptibility of cis-diamminedichloroplatinum-treated K562 cells to lysis by peripheral blood lymphocytes and lymphokine activated killer cells.

BACKGROUND: Previous studies have reported that cis-diamminedichloroplatinum (II) (CDDP) exhibits various immunomodulating activities. The current study investigates the effect of CDDP on the susceptibility of K562 cells to lysis by peripheral blood lymphocytes (PBL), natural killer (NK) cells, and lymphokine activated killer (LAK) cells. METHODS: Cytotoxicity was determined by the 51Cr release assay. RESULTS: Treatment of K562 cells with CDDP at 10 micrograms/ml or more for 3 hours or more enhanced their susceptibility to lysis by PBL. This CDDP-mediated enhancement of lysis was observed by PBL derived from healthy donors and from patients with urinary bladder tumor or with other malignant and nonmalignant urologic diseases. The CDDP-induced enhancement of K562 cell susceptibility to lysis by PBL also was observed when purified NK cells and LAK cells were used as effector cells. The CDDP analog, carboplatin, enhanced the susceptibility of K562 cells to lysis by PBL, but treatment with transdiamminedichloroplatinum (II) had no effect. Several experiments were done to investigate the mechanism of the enhanced susceptibility of CDDP-treated K562 cells to lysis by PBL. Treatment of K562 cells with CDDP had no effect on the expression of major histocompatibility complex (MHC) Class I, MHC Class II, neural cellular adhesion molecule, and leukocyte function antigen-1 on the tumor cells. The frequency of target cell conjugates to PBL was not changed by CDDP-treated K562 cells. Pretreatment of K562 cells with CDDP and lysosomotrophic agents (L-leucine-methyl-ester or chloroquine) abrogated their enhanced susceptibility to lysis by PBL. CDDP treatment of K562 cells did not augment their sensitivity to alpha-interferon, gamma-interferon, tumor necrosis factor alpha, or natural killer cytotoxic factor (NKCF). Treatment of effector cells with CDDP had no effect on their cytotoxic function. CONCLUSIONS: These results demonstrate that CDDP has a direct effect on the K562 target cells, rendering them more susceptible to lysis by PBL, NK cells, and LAK cells. In addition, the result suggest that CDDP-mediated enhancement of target cell lysis is not attributable to changes of surface membrane antigen expression or recruitment of precursor cells but to processing of CDDP by the cells. The possible mechanisms of the effect of CDDP on K562 cells and clinical implications are discussed.

Aged↗
PubMed1993

Killer cell recruitment and renewal capacity of purified cytolytic and noncytolytic human peripheral blood natural killer cell subsets.

The inability to isolate NK precursors at different stages of development has impeded understanding of the processes involved in NK maturation. The present studies utilize a flow cytometric technique that enables the isolation of operationally defined cell subsets, lytic (killers) and nonlytic conjugate-forming (binders), and nonconjugate-forming (free) cells, within NK-enriched preparations to test whether these might represent cells in different stages of NK development. To characterize both the steps involved in NK maturation and the cells responsible for IL-2 induced proliferation, these purified subsets were analyzed for their killer cell recruitment and renewal capacity. After a 2-h exposure to IFN-alpha or IL-2, induction of lytic function was developed only in the binder subset as detected in the single cell assay. Neither enhancement of killer cell recycling nor induction of binding function among the subsets was observed. However, after an 18-h culture period, with or without rIL-2, killer cells preferentially expressed activation Ag CD69 (Leu-23) and the IL-2R alpha-chain, TAC (CD25). In addition, all cells in contact with K562 targets displayed enhanced expression of these Ag. Killer cells also showed an enhanced capacity to proliferate in response to rIL-2 in a 6-day [3H]TdR incorporation assay. Additional irradiated K562 targets enhanced the proliferative capacity of all the subsets, with only a marginal effect on sorted free cells. Nevertheless, sorted free cells, in addition to binders, developed potent binding and lytic function when tested in the single-cell assay after 4 days of IL-2 culture. The lytic activity of killers was reduced, as compared with freshly isolated killers. The results are consistent with a two-step model for NK maturation, involving the acquisition of lytic function before proliferative capacity, and specific triggering of killer cells through interaction with target cells for induction of a proliferative competent state.

Antigens, Differentiation↗