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D A Chow

Publications and source records attributed to D A Chow.

At least 19 recordsLinked to original sources
PubMed2000

Natural antibody-induced intracellular signalling and growth control in C3H 10T1/2 fibroblast variants.

Cell-surface binding by natural antibody (NAb) places it well for controlling cell function directly through signalling. Flow cytometry revealed an instability of syngeneic NAb binding to C3H 10T1/2 fibroblast variants at 37 degrees, which could be partially reduced by H7, an inhibitor of the pivotal signalling serine/threonine kinase, protein kinase C (PKC). Cells coated with purified NAb at 4 degrees followed by a rise in temperature to 37 degrees showed an increase in membrane expression of introduced rat PKC-beta 1 and endogenous PKC-alpha, in the PKC-beta 1-overexpressing PKC-4 and v-H-ras-producing I3T2.1, respectively. Tyrosine phosphorylation of membrane-associated 60 000 MW protein including the tyrosine kinase src was markedly reduced. In addition, both the precoated NAb and numerous membrane molecules ranging from 20,000 to 220,000 MW were released into the supernatant, including the receptor-like protein tyrosine phosphatase alpha (RPTP-alpha). Furthermore, purified NAb reduced the growth of I3T2.1 cells in culture assessed as a decrease in total cell numbers and an increase in the proportion of cells in the G0/G1 phase of the cell cycle. Together, these data argue that the interaction of NAb with cell surface structures initiated a series of intracellular signalling events leading to the release of membrane molecules and over time the suppression of cell proliferation. This process could provide a biological mechanism for direct NAb control of activated cells in both physiological and pathological conditions.

Animals↗
PubMed2000

Natural immunity and neuroimmune host defense.

Innate resistance is mediated by non-immune defense and by natural immunity. Non-immune defense includes diverse mechanisms (e.g., physico-chemical defense by bile acids). Natural killer (NK) cells, gamma delta T lymphocytes and CD5+ B lymphocytes are key mediators of natural immunity. These cells utilize germ-line coded receptors that recognize highly conserved, homologous epitopes (homotopes). Typically, it is not the antigen, but cytokines and hormones that regulate the level of NK-mediated cytotoxicity. These include interleukin-2, interferons, prolactin and growth hormone. Less is known about gamma delta T lymphocytes. CD5+ B lymphocytes produce germ-line coded antibodies (predominantly IgM) that are polyspecific, and able to recognize a great variety of microorganisms, cancer-cells and self-components. Antigen is not an effective stimulus for natural antibody (NAb), but bacterial lipopolysaccharide (LPS) is. During the acute phase response (febrile illness) the T-cell-regulated adaptive immune response is switched off and natural immune mechanisms are amplified several hundred to a thousand times within 24-48 hours (immunoconversion). This immunoconversion is initiated by immune-derived cytokines, and involves profound neuroendocrine and metabolic changes, all in the interest of host defense. Immune recognition is assured by natural antibodies and by some liver-derived acute phase proteins, such as C-reactive protein or endotoxin-binding protein, the level of which is elevated in the serum. Thus, natural immunity is essential for a first and last line of defense and the neuroendocrine system is an important promoter of this activity.

Animals↗
PubMed1999

Protein kinase C expression links natural antibody binding with surveillance of activated and preneoplastic cells.

Extensive evidence supports a role for natural antibody (NAb) acting against small tumour foci in vivo. Ras-transformation of murine C3H 10T 1/2 fibroblasts, known to partially activate and down-regulate endogenous PKC-alpha, increased their serum NAb-binding capacity consistent with the requirements for natural immune surveillance. Now a rat PKC-beta1-overexpressing 10T 1/2 clone, PKC-4, with an 11-fold increase in PKC activity and an activated, partially transformed phenotype, links higher susceptibility to transformation through v-Ha-ras infection with an 80% increase in NAb binding assayed by flow cytometry. H7 and E-64d inhibition and phorbol ester depletion of PKC reduced NAb binding. PKC-beta1 expression and NAb binding exhibited a similar temporal recovery from TPA treatment. Thus, expression of NAb-binding structures appears to be elevated by constitutive increases in the basal activation of PKC in both the ras-transformation and the PKC-beta1-preneoplasia models. This, coupled with corresponding decreases in membrane PKC-alpha and NAb binding in confluent 10T 1/2 cells raises the possibility that in general, cells activated through PKC are NAb sensitive. Together with the increased in vivo elimination of the high NAb-binding PKC-4 cells, the data extend the support for a role for NAb in immune surveillance, to resistance against preneoplastic cells, and argue for NAb contributing to homeostasis of the organism.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1998

Neuroimmunoregulation and natural immunity.

The development and function of the immune system is regulated by neuroendocrine factors. Immune function may be divided into adaptive and natural immunity. Adaptive immune responses are driven by specific determinants of the antigen (epitopes), require 5-10 d to fully develop, and show an accelerated or memory response after repeated exposure to the same antigen. Natural immunity may be divided into host defense mediated by non-immune factors (e.g., antimicrobial proteins, enzymes, mucus etc.) and polyspecific responses of the immune system. This polyspecific response relies on natural antibodies and on some other serum proteins (e.g., lipopolysaccharide-binding protein-LBP, C-reactive protein-CRP), and on surface receptors of macrophages, natural killer cells and B and T lymphocytes for activation. Highly conserved homologous (crossreactive) epitopes, or homotopes for short, are recognized by the natural immune system. Natural antibodies, LBP, and CRP are capable of activating the entire immune system after combination with the appropriate homotope. During febrile illness natural immune host defense is promptly elevated because of the rapid rise of natural antibodies, LBP, and CRP in the serum. This is known as the acute phase response (APR), which is initiated by a sudden rise of cytokines in the circulation, such as IL-1, IL-6, and TNF-alpha. The cytokines act on the brain, the neuroendocrine system, and on other tissues and organs, which leads to fever and profound hormonal and metabolic changes. The hypothalamus-pituitary adrenal axis is activated and serves as the primary regulator of immune and inflammatory reactions. Insulin, glucagon, and catecholeamine levels are also raised. Bone marrow activity and leukocyte function are high and the liver is converted to the rapid production of acute-phase proteins (APP). APP include LBP, CRP, fibrinogen, some complement components, enzyme inhibitors, and anti-inflammatory proteins, which may rise in the serum from several hundred to a thousand times within 24-48 hr. Therefore, natural immunity is a polyspecific response to homotopes, which functions as an instantaneous defense mechanism in health and which is rapidly boosted by cytokines and hormones during febrile illness. This is a highly successful defense reaction, as in the overwhelming majority of cases, febrile illness leads to recovery and the development of adaptive immunity in man and higher animals.

Acute-Phase Reaction↗
PubMed1998

Neuroimmunoregulation and cancer (review).

It is certain that neuroimmune mechanisms play a role in host defence against cancer. However, this interaction is highly complex and many variations are possible according to the nature of the neoplasms involved. There are indications that adaptive immunity is present in a significant proportion of tumor bearing hosts, and this defence may be boosted by specially designed vaccines and cytokines. Natural immune mediators are also implicated in resistance against tumor development. Here we review the evidence suggesting that hormonal manipulation of the host can result in the elevation of immune defences against cancer. Such manipulation strengthens both the adaptive and natural immune defences of the host, both of which play significant roles. Natural defence mechanisms are boosted by cytokines and hormones during febrile reactions which are now known as the acute phase response. It is suggested that hormonal stimulation of immune mechanisms coupled with the usual immunostimulants already in use may be employed to good advantage for the combination immunotherapy of cancer. Modern molecular biology approaches permit the development of laboratory monitoring procedures which may be used for the prediction and follow-up of therapeutic success.

Acute-Phase Reaction↗
PubMed1997

Differential CD45 isoform expression accompanies reduced natural antibody binding in L5178Y-F9 tumor progression.

Considerable evidence supports a role for polyclonal serum natural Ab (NAb) as a mediator of natural resistance against tumors. However, the molecular mechanisms of this NAb activity are not known. Flow cytometry selection of L5178Y-F9 murine T lymphoma cells for high NAb binding provided the variant LYNAb+, which exhibited an inversely corresponding reduction in tumorigenicity. Accompanying the increased NAb binding, LYNAb+ bound more monoclonal 14.8 anti-CD45RA and DNL-1.9 anti-CD45RC and less 13/2 anti-pan CD45, and the binding of MB23G2 anti-CD45RB was eliminated. However, neuraminidase treatment increased NAb binding and detection of pan CD45, CD45RA, and CD45RC but reduced CD45RB expression, suggesting that the epitopes recognized by the former Abs are masked by sialic acid, while the latter includes sialic acid. Growth of the LYNAb+ from a threshold s.c. inoculum in syngeneic DBA/2 mice yielded more tumorigenic cells which bound less NAb, anti-CD45RA, and anti-CD45RC; the same very low anti-CD45RB; and more anti-pan CD45. In accord with the mAb binding, the L5178Y-F9 and an in vivo passaged LYNAb+ variant expressed predominantly lower m.w. CD45 isoforms while the LYNAb+ expressed predominantly higher 200-kDa isoforms. The consistent correspondence between CD45RA and CD45RC determinant expression, CD45 isoform expression, tumorigenicity, and NAb binding exhibited by T lymphoma cells selected for high NAb binding in vitro or through tumor progression in vivo suggests that asialo high m.w. isoforms of the cell surface-signaling molecule CD45 are differentially expressed during tumor development and furthermore that they participate in NAb-mediated antitumor mechanisms.

Animals↗
PubMed1995

Reduced tumorigenicity of threshold syngeneic tumor inocula in xid-bearing mice treated with natural antibodies.

Several correlative experimental approaches have provided evidence that polyclonal serum natural antibodies (NAb) participate in the defense against small syngeneic tumor foci in vivo. The threshold subcutaneous tumor inoculum model of incipient neoplasia has consistently revealed an inverse relationship between tumorigenicity in vivo and the NAb binding capacity of the tumor injected or the anti-tumor NAb levels of the recipient animals, including B cell-deficient mice bearing the xid mutation of the CBA/N mouse strain. Now passive i.v. administration of whole normal syngeneic serum NAb in bolus injections, given I each day beginning on day -2, -1 or 0 prior to the threshold s.c. challenge of xid-bearing CBA/N or male (CBA/N x CBA/J)F1 mice with syngeneic RI-28 lymphoma cells, consistently and significantly reduced their tumorigenicity assayed as tumor appearance and latency. Three similar injections of an ammonium sulfate-precipitated fraction of whole serum NAb also reduced tumor frequency and latency, while a combination of purified IgG and IgM NAb reduced the appearance of tumors slightly and increased the survival of recipients. The reconstitution of the xid-defect in anti-tumor NAb provides more direct evidence to substantiate a role for NAb in the defense against early tumor development in vivo and establishes a model for the dissection of the in vivo mechanisms of the NAb anti-tumor activity.

Animals↗
PubMed1995

Probucol protects against adriamycin cardiomyopathy without interfering with its antitumor effect.

BACKGROUND: The usefulness of adriamycin (ADR), a potent antitumor antibiotic, is limited by the development of life-threatening cardiomyopathy and congestive heart failure. Subcellular changes leading to heart failure are suggested to be mediated by a drug-induced increase in free radicals and lipid peroxidation. In an earlier study, concurrent treatment with probucol (PROB), a lipid-lowering drug with strong antioxidant properties, was shown to offer only partial protection against ADR cardiomyopathy. The present study had two aims: to determine whether this protective effect can be improved further by extended treatment with PROB, and to determine whether PROB affects the antitumor properties of ADR. METHODS AND RESULTS: ADR (cumulative dose, 15 mg/kg body wt) was administered in rats in six equal injections (IP) over a period of 2 weeks. Three weeks after the end treatment, cardiomyopathy and congestive heart failure were characterized by ascites, congested liver, depressed cardiac function, elevated left ventricular end-diastolic pressure, and myocardial cell damage. Myocardial glutathione peroxidase (GSHPx) activity was decreased and lipid peroxidation was increased. Administration of PROB (cumulative dose, 120 mg/kg body wt) in 12 equal injections (IP), before and concurrent with ADR, completely prevented these cardiomyopathic changes, normalized left ventricular function, lowered mortality, and eliminated ascites. Treatment with PROB was also accompanied by an increase in myocardial GSHPx and superoxide dismutase activities with a concomitant decrease in lipid peroxidation. Tumor regression in syngeneic DBA/2 mice inoculated with L5178Y-F9 lymphoma cells in the ADR+PROB group was significant and comparable to the ADR group. CONCLUSIONS: These data show for the first time that PROB can provide complete protection against ADR cardiomyopathy without interfering with antitumor properties of the drug. This protective effect of PROB may be related to the maintenance of the antioxidant status of the heart.

Animals↗
PubMed1992

Tumor progression in vivo: increased soybean agglutinin lectin binding, N-acetylgalactosamine-specific lectin expression, and liver metastasis potential.

Tumors which grew out from threshold s.c. inocula of L5178Y-F9 and SL2-5 murine T-cell lymphomas in syngeneic DBA/2 mice exhibited a unified natural defense-resistant phenotype including an increased tumorigenicity and correlating reductions in susceptibility to natural antibodies, natural killer cells, and activated macrophages in vitro. The metastatic potential and cell surface saccharide expression of these cells were determined to assess the impact of growth from a small tumor focus in vivo on subsequent metastatic ability and to determine whether there was any association with changes in cell surface carbohydrates, which have been implicated now for many years in tumor development. A significantly increased liver-colonizing ability was observed following i.v. injection. The most consistent change in cell surface saccharide expression detected in studies using five lectins was an increase in N-acetyl-D-galactosamine (D-GalNAc)-specific soybean agglutinin (SBA) binding. The log of experimental liver metastasis, SBA binding, and the percentage of hepatocyte rosetting of the parental and in vivo-selected cells exhibited significant direct correlations. While inhibition of rosetting with in vivo-selected lines by D-GalNAc and galactose was consistent with the involvement of the D-galactose/D-GalNAc-specific hepatocyte receptor, preincubation of the tumor cells but not hepatocytes with D-GalNAc inhibited hepatocyte rosetting and D-GalNAc inhibited homotypic tumor cell binding. These data suggest a role for a saccharide-specific, lectin-like receptor on tumor cells in both interactions and therefore in the increased experimental liver metastasis. Furthermore, the increased expression of D-GalNAc-inhibitable SBA binding sites on the in vivo-selected variants should increase the homotypic binding by the D-GalNAc-specific lectin-like receptors on the tumor cells providing a rationale for the direct relationship observed between increased SBA binding and i.v. metastatic potential.

Acetylgalactosamine↗
PubMed1992

Regulation of natural antibody binding and susceptibility to natural killer cells through Zn(++)-inducible ras oncogene expression.

Changes in the natural resistance phenotype were examined for the 2H1, 10T 1/2 cells expressing the activated human H-ras oncogene under the transcriptional regulation of the zinc-inducible mouse metallothionein-I promoter. Culture of the cells in 50 microM ZnSO4 induced an increase in ras protein p21 levels which were maximal within 1 day. Natural-antibody (NAb) binding was significantly increased following 2 days of cell culture in ZnSO4 and continued to increase up to 4 days. The increased NAb binding returned to uninduced levels within 2 days following the removal of added zinc ions from the culture medium. The cells also exhibited a significant increase in natural killer (NK) cell sensitivity following 2 days in ZnSO4. This was maintained as long as the zinc was in the medium, but returned to uninduced levels within 1 day following its removal. The results show that NAb binding and susceptibility to NK cells increased following ras oncogene expression in 10T 1/2 cells and that both parameters were regulated by p21 expression. Repeated i.v. administration of whole-serum NAb prior to tumor inoculation reduced the number of early tumors following s.c. injection of Zn(++)-induced 2Hl cells into Zn(++)-treated C3H/HeN mice, consistent with an in vivo role for NAb in the defense against ras-transformed cells. In contrast, small but statistically significant reductions in NAb binding were observed following v-H-ras transformation of NIH 3T3 cells or v-src transformation of 10T 1/2. The data argue for an NAb- and NK-cell-susceptible phase of ras-induced tumor development which is a prerequisite for these mediators to contribute to a first line of defense against incipient neoplasia, and suggest that characteristics of the recipient cell and the transforming oncogene are important in determining the natural resistance phenotype.

3T3 Cells↗
PubMed1992

Polyclonal natural antitumor antibody binding dynamics: preferential release of surface membrane molecules and increased metastasis.

Flow cytometry revealed the dynamic nature of polyclonal whole serum naturally occurring IgG and IgM antibody binding to the syngeneic murine T cell lymphomas SL2-5, L5178Y-F9 and the in vitro selected high natural antibody binding variant L5178Y-F9 TPA/NAb+3. This was particularly evident at physiological conditions where the temperature was 37 degrees C and the concentration of reactive serum natural antibodies (NAb) was high. Lower binding was observed at 37 versus 4 degrees C, or after raising the temperature from 4 to 37 degrees C, a procedure which was associated with an augmented loss of 125I-surface-labelled material from cells incubated in NAb compared to cells exposed to growth media. Even at 4 degrees C, NAb binding exhibited biphasic kinetics suggesting a loss of surface-bound NAb and a subsequent cycle of NAb uptake. The increased intravenous liver metastasis potential of the high NAb binding L5178Y-F9 TPA/NAb+3 corresponded with its higher total loss of 125I-surface-labelled material when incubated in NAb at 37 degrees C, and with its extensive loss of NAb binding when the temperature was raised from 4 to 37 degrees C. These observations are consistent with the idea that molecules released from the cell may contribute to the higher metastasis. This thinking was supported by the increased metastasis of tumor cells injected intravenously, either with serum in which they had been preincubated at 37 degrees C or into mice treated with supernatants from tumor cells incubated in NAb.

Animals↗
PubMed1991

RNK granule extract cytolysis: increased tumor susceptibility and release of proteochondroitin sulphate inhibitor in high NaCl.

The insensitivity of the natural killer (NK)-resistant L5178Y-F9 murine T-cell lymphoma to granule extracts from a rat NK leukemia could be preferentially reversed in increased NaCl (0.25 M) compared with the NK- and granule extract-sensitive SL2-5. The high salt effect predominated in the binding rather than the lytic phase of the extract reaction similar to the activity of extract inhibitory supernates preferentially produced from L5178Y-F9 cells. Exposure of the L5178Y-F9 to 0.25 M NaCl was associated with an increased production of inhibitory supernate and an increased sensitivity of the cell as an extract target. Pretreatment of inhibitor-containing supernatant or inhibitor-producing L5178Y-F9 cells with pronase or chondroitinase AC reduced the inhibitory activity of the resultant supernates, and L5178Y-F9 supernates treated with anti-chondroitin sulphate AC antibodies exhibited reduced inhibitory activity. These observations and the previously reported molecular weight heterogeneity and protease sensitivity of the inhibitor argue that chondroitin sulphate AC-containing proteoglycans released from the tumor cell surface may inhibit cytolysin activity, contributing to the preferential resistance of the L5178Y-F9 to rat NK granule extract cytolysis.

Animals↗
PubMed1991

Natural antibody recognition of v-H-ras-induced 10T1/2 transformation.

An increasing body of evidence supports a role for natural antitumor antibodies acting against tumors in vivo. However, a role for natural antibodies (NAb) in tumor surveillance would imply that sensitivity to NAb should increase following events associated with cellular transformation. To test this prediction we examined by flow cytometry the effect on serum NAb binding of v-H-ras expression and integration in 10T1/2. The co-introduction of v-H-ras and the neomycin resistance (neor) gene into 10T1/2 followed by G418 selection resulted in a marked and heterogeneous increase in NAb binding. Clonal analysis of this population demonstrated that the increased NAb binding was associated with tumorigenic conversion and ras-p21 expression. The results provide the first evidence for a NAb-susceptible phase of ras-induced transformation.

Animals↗
PubMed1991

Inverse correlation between natural antitumor antibodies and tumor susceptibility in individual xid-bearing mice.

Natural antibodies (NAb), natural killer (NK) cells and activated macrophages have all been implicated in the rejection of threshold syngeneic tumor inocula. Previous analysis of tumor susceptibility in normal versus inbred and F1 mice bearing the B cell deficiency associated with the xid mutation of CBA/N mice demonstrated an inverse relationship between the tumorigenicity of the RI-28, a radiation-induced leukemia of the CBA/H strain, and the pooled anti-RI-28 serum NAb levels in mice with the same genetic origins. No relationship with tumor susceptibility was seen with NK cell or in vivo activated macrophage cytolysis. Flow-cytometric determination of antitumor serum NAb bled from individual male and female (CBA/N X CBA/J)F1 mice 1 week prior to the threshold tumor inoculation has revealed extensive heterogeneity within the NAb levels of each sex. A comparative analysis of tumor fate with NAb activity revealed that tumors appeared in only 26.3% of animals with a mean fluorescence channel binding above 60 channels in contrast with 77.3% of animals with lower NAb levels. These data extend to the level of individual hosts the support for an inverse relationship between host NAb activity and tumor susceptibility. In addition, subsequent analysis of serum antitumor NAb levels, splenic NK cytolysis and in vitro lymphokine-activated macrophage activity with all three mediators originating from the same individual F1 mice showed no consistent correlations between these natural resistance activities, arguing for the exclusion of deficiencies in NK cell or macrophage function as the basis for the differential tumor susceptibility in individual F1 mice.

Animals↗
PubMed1990

RNK granule extract cytolysis: differential inhibitor production by an NK-resistant vs an NK-sensitive murine lymphoma.

Natural killer (NK) cell-resistant tumors exist despite their ability to bind cells from the effector population. Tumor sensitivity to NK activity was therefore examined at the level of susceptibility to cytolysin-containing NK cell cytotoxic granule extracts. The NK-sensitive SL2-5 murine lymphoma was markedly more susceptible than the NK-resistant L5178Y-F9 to solubilized granule preparations from the rat NK tumor cell line RNK-16, and this corresponded also with tumor sensitivity to hypotonic lysis. However, the resistant L5178Y-F9 was better able to inhibit the extract activity than the SL2-5. Dissociation of the binding and lysis phases of the cytolysin reaction based on their differential temperature requirements, 4 degrees C for binding and 37 degrees C for lysis, permitted an examination of the cytolysin/tumor interaction prior to lysis. The residual cytotoxic activity was lower after extract exposure to the L5178Y-F9 compared with the SL2-5 consistent with possible inhibitor production. Finally, supernatant material collected from the L5178Y-F9 was a better inhibitor of granule extract lysis and acted preferentially in the extract-binding phase. The inhibitor appears to be protein in nature, relatively stable, and exhibits molecular weight heterogeneity ranging from 2000 to greater than 300,000.

Animals↗
PubMed1989

Low natural antibody and low in vivo tumor resistance, in xid-bearing B-cell deficient mice.

Evidence from correlative studies and Winn-type assays in syngeneic murine models has suggested that natural antibodies contribute to resistance against tumors in vivo. The B cell deficit associated with the X-linked immunodeficiency of CBA/N strain mice provided a genetic model in which to further test this question. RI-28, a radiation-induced T cell leukemia of the CBA/H strain acquired reduced levels of fluorescence-detected natural antibodies from the serum of X-linked immunodeficiency-bearing CBA/N and male (CBA/N x CBA/J) F1 mice compared with the serum from normals. Threshold s.c. inocula of the RI-28 appeared sooner and produced higher tumor frequencies in the X-linked immunodeficiency-bearing animals. This data coupled with the lack of correlating deficiencies in natural killer cell or activated macrophage activity provide the first genetic evidence for the hypothesis.

Animals↗
PubMed1988

Tumorigenicity of murine lymphomas selected through fluorescence-detected natural antibody binding.

Fluorescence-activated cell sorting was used to isolate high and low IgM natural antibody (NAb) binding populations from a heterogeneous line of the L5178Y-F9 murine lymphoma. The ranking of NAb binding and complement-dependent NAb lysis of the selected and starting lines were the same and opposite to that of their tumorigenicity in syngeneic DBA/2 mice. L5178Y-F9 and SL2-5 clones repeatedly treated with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate and selected by fluorescence-activated cell sorting for high NAb binding exhibited increases in NAb binding and sensitivity to complement-dependent NAb lysis which corresponded with reduced tumor frequencies of threshold inocula. Although the high NAb binding SL2-5 line was slightly more sensitive to natural killer (NK) cell cytolysis, changes in susceptibility to activated macrophages or hypotonic lysis were not consistent with the observed reductions in tumor frequency so that the selected alterations in NAb binding corresponded best with tumorigenicity. These data confirm the same inverse relationship exhibited previously by in vivo and in vitro selected tumor variants and provide more precise evidence supporting a role for NAb in host resistance against tumor foci.

Animals↗