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At least 163 records · Page 9Linked to original sources
PubMed1992

Evidence that the transcriptional trans-activating function of the bovine papillomavirus type 1 E2 gene is not required for viral DNA amplification in division-arrested cells.

Amplification of bovine papillomavirus type 1 (BPV-1) DNA in growth-arrested mouse cell cultures appears to mimic the process of induction of vegetative BPV-1 DNA synthesis in cells of the stratum spinosum in productively infected bovine warts. In both cases, cells permissive for viral DNA amplification express large amounts of viral E2 protein which accumulates within the cell nucleus. Whereas in latently infected virus-transformed cells truncated transcriptional repressor forms of E2 predominate, our previous studies have demonstrated that the full-length E2 transcriptional trans-activator protein is preferentially expressed during the period of maximal BPV-1 DNA amplification in growth-arrested cell cultures. To investigate the role of the full-length E2 gene in the induction of viral DNA amplification in this experimental viral replication system we have used a mutant BPV-1 genome (BPVE2-ts1) containing an E2 gene which is temperature-sensitive (ts) for transcriptional trans-activation. This mutant genome has also been shown to be ts for stable viral plasmid DNA replication and for the induction of cell transformation. We show here that viral DNA amplification was not severely impaired when BPVE2-ts1-transformed cells were tested at the restrictive temperature, indicating that the transcriptional trans-activating function of E2 was not essential for viral DNA amplification in division-arrested cells and, moreover, that the trans-activation and replication functions of E2 were separable. Consistent with this hypothesis, amplification of the BPVE2-ts1 genome at the restrictive temperature was still associated with the accumulation of large amounts of nuclear E2 antigen, showing that the mutation did not disrupt nuclear transport or render the E2 protein highly unstable. Furthermore, C127 cells harbouring ts E2 and full-length E1 expression constructs supported transient plasmid replication of a BPV origin vector at the restrictive temperature. These observations imply that E2 functions primarily as a viral replication factor in the vegetative phase of BPV-1 DNA replication, and suggest a fundamental difference in the genetic regulation of stable BPV-1 plasmid DNA replication in mitotic cells and viral DNA amplification in postmitotic cells.

Animals↗
PubMed2002

The cold-inducible icl gene encoding thermolabile isocitrate lyase of a psychrophilic bacterium, Colwellia maris.

The gene encoding isocitrate lyase (ICL; EC 4.1.3.1) of a psychrophilic bacterium, Colwellia maris, was cloned and sequenced. The ORF of the gene (icl) was 1584 bp long, and the predicted gene product consisted of 528 aa (molecular mass 58150 Da) and showed low homology with the corresponding enzymes from other organisms. The analyses of amino acid content and primary structure of the C. maris ICL suggested that it possessed many features of a cold-adapted enzyme. Primer extension and Northern blot analyses revealed that two species of the icl mRNAs with differential lengths of 5'-untranslated regions (TS1 and TS2) were present, of which the 5' end (TS1 and TS2 sites) were G and A, located at 130 and 39 bases upstream of the translation start codon, respectively. The levels of TS1 and TS2 mRNAs were increased by both acetate and low temperature. The induction of icl expression by low temperature took place in the C. maris cells grown on succinate as the carbon source but not acetate. Furthermore, a similar manner of inductions was also found in the levels of the translation and the enzyme activity in cell-free extract. These results suggest that the icl gene, encoding thermolabile isocitrate lyase, of C. maris is important for acetate utilization and cold adaptation.

Alteromonadaceae↗
PubMed2005

The manganese-responsive repressor Mur of Rhizobium leguminosarum is a member of the Fur-superfamily that recognizes an unusual operator sequence.

The manganese uptake regulator Mur of Rhizobium leguminosarum is a close homologue of the global iron regulatory protein Fur. Mur represses the sitABCD operon, which encodes a Mn2+ transport system, specifically in response to Mn2+ but not Fe2+. In previous work the authors mapped the 5' ends of two sit operon transcripts, termed TS1 and TS2, which were co-ordinately regulated by Mn2+-Mur, but this paper now shows that only TS1 is a primary transcript. DNase I protection analyses showed that purified Mur bound, with similar affinity, to two sites in the regulatory region of sitABCD, but only when Mn2+ was present in the reaction buffer. These Mn2+-Mur-binding sites, termed MRS1 and MRS2 (Mur-responsive sequence), were closely related in sequence to each other and were separated by 16 bp, spanning the transcription initiation site TS1. The extent of the protected DNA was 34 and 31 bp for MRS1 and MRS2, respectively, which is in accord with other members of the Fur family. The DNA sequences recognized by Mn2+-Mur are wholly different from conventional Fur boxes, but some similarities to a recognition sequence for the Fur regulator from Bradyrhizobium japonicum were noted. Transcription analysis of the R. leguminosarum mur gene showed its expression to be independent of Mn2+-Mur. Thus, Mur is a sequence-specific DNA-binding protein that responds in vitro to manganese, and thus can occlude RNA polymerase access to the sitABCD promoter. Moreover, Mur recognizes a DNA sequence atypical for the Fur superfamily and, like Fur from B. japonicum, defines a new subclass of Fur-like transcriptional regulators.

Bacterial Proteins↗
PubMed1991

Effects of Cryptococcus neoformans-specific suppressor T cells on the amplified anticryptococcal delayed-type hypersensitivity response.

Cell-mediated immunity is an important host resistance mechanism against Cryptococcus neoformans, the etiological agent of cryptococcosis. Previous studies from our laboratory have shown that the anticryptococcal cell-mediated immune response as measured by delayed-type hypersensitivity (DTH) is down-regulated by a cascade of antigen-specific T suppressor (Ts) cells. Recently, we have identified a population of CD4 T cells that up-regulate the anticryptococcal DTH response (Tamp cells). The Tamp cells are found in the spleens of donor mice at 6 days after immunization with cryptococcal antigen, and they amplify the anticryptococcal DTH response when transferred to syngeneic recipients at the time of immunization of the recipients. In this study, we determined the effects of C. neoformans-specific Ts cells on the induction of the Tamp cells in the Tamp cell-donor mice and on the induction and expression of the amplified anticryptococcal DTH response in the Tamp cell-recipient mice. When cryptococcal-specific Ts1 cells were given at the time of immunization of the Tamp cell-donor mice, induction of Tamp cells was inhibited. In contrast, when Ts1 cells were given at the time of adoptive transfer of Tamp cells, the recipients displayed amplified DTH responses, indicating that Ts1 cells do not affect the Tamp cells' function once the Tamp cells have been produced. C. neoformans-specific Ts2 cells given at the time of either immunization or footpad challenge of the Tamp cell-recipient mice did not alter, to any measurable extent, the amplified DTH response. These results indicate that in addition to amplifying the anticryptococcal DTH response, Tamp cells may protect the anticryptococcal TDH cells from suppression by C. neoformans-specific Ts cells, much like contrasuppressor cells do in other systems. However, further characterization of the Tamp cells revealed that they are not adherent to Viscia villosa lectin, indicating that the anticryptococcal Tamp cells do not have this characteristic in common with contrasuppressor cells of other antigen systems.

Animals↗
PubMed1994

Regulation of cytokine production during the expression phase of the anticryptococcal delayed-type hypersensitivity response.

Effects of both positive and negative regulatory T cells on cellular infiltration and cytokine production during the expression phase of the anticryptococcal immune response were examined. Tamp cells, which are induced by cryptococcal antigen, significantly amplify the anticryptococcal delayed-type hypersensitivity response, whereas a cascade of T suppressor (Ts) cells inhibits the response and decreases the clearance of Cryptococcus neoformans during an infection. By using the gelatin sponge implantation model, we found that Tamp cells do not stimulate a significant increase in cellular infiltration into the sponges in response to cryptococcal antigen compared with that into delayed-type hypersensitivity-reactive sponges in immune control mice. However, Tamp cells do stimulate significant increases in the production of gamma interferon and interleukin-2 (IL-2) in the antigen-injected sponges over the level of the representative cytokine in antigen-injected sponges from the immune control mice. Likewise, Ts1 cells, induced with cryptococcal antigen, do not significantly affect antigen-induced cellular infiltration into sponges in immune mice. In contrast, decreased levels of gamma interferon and IL-2 are observed in antigen-injected sponges from Ts1-cell-recipient, immunized mice compared with those of the positive immune controls. The presence of either Tamp or Ts1 cells in immunized mice stimulates increased production of IL-5 but not IL-4 over that of the positive immune controls.

Animals↗
PubMed1971

Isolation of temperature-sensitive conditional lethal mutants of "fixed" rabies virus.

In an attempt to induce temperature-sensitive (ts) conditional lethal mutants of rabies virus, stocks of a plaque-purified substrain of strain CVS fixed rabies virus were subjected to mutagenesis by HNO(2), 5-fluorouracil, or 5-azacytidine. It was necessary to prepare virus stocks from clones of mutagenized virus selected at random and to test subsequently each stock for possible ts characteristics by measuring its relative capacity for growth at permissive (33 C) and nonpermissive (40.5 C) temperatures. Five ts mutants were detected in tests of 161 clones of mutagenized virus. Each of the mutants exhibited a remarkably low incidence of reversion and little demonstrable "leakiness." One of the five ts mutants (ts2), which formed formed very small plaques, and another (ts1), which formed plaques of only slightly reduced size, were further characterized. Virus ts1 was more thermostable at 40.5 C than the parental virus, but the ts2 mutant was unchanged in this respect. The ts1 virus exhibited normal pathogenicity for mice, but ts2 virus caused a very irregular death pattern. Both deaths and survivors immune to rabies virus challenge were noted in all groups of mice inoculated with ts2 virus, regardless of the virus dose.

Animals↗
PubMed2000

Bedside detection of retained tracheobronchial secretions in patients receiving mechanical ventilation: is it time for tracheal suctioning?

OBJECTIVE: To identify parameters that indicate retained secretions and the need for tracheal suctioning (TS) in patients receiving mechanical ventilation (MV). DESIGN: Prospective observational study. SETTING: A 14-bed medical ICU in a 946-bed university hospital. PATIENTS: Sixty-six consecutive patients receiving MV. INTERVENTIONS: Two successive tracheal suctions, TS1 and TS2, performed at a 2-h interval as usual patient care. Retained secretions were considered significant if the volume of secretions removed by TS2 was > 0.5 mL. MEASUREMENTS AND RESULTS: Variations between TS1 and TS2 of pulse oximetric saturation (SpO(2)), peak inspiratory pressure (Ppeak), tidal volume (VT), and Ramsay score were compared between patients with TS2 < or = 0.5 mL (group 1; n = 27) and patients with TS2 > 0.5 mL (group 2; n = 39). The presence of a sawtooth pattern on flow-volume loop displayed on the monitor screen of the ventilator and of respiratory sounds heard over the trachea before TS2 were compared between the two groups. Variations of Ppeak, VT, SpO(2), and Ramsay score between TS1 and TS2 did not differ between the two groups. However, group 2 had a sawtooth pattern (82% vs 29.6%; p = 0.0001) and respiratory sounds (66.6% vs. 25.9%; p = 0. 001) more frequently than group 1 before TS2. For the sawtooth pattern, the likelihood ratio (LR) of a positive test was 2.70 and the LR of a negative test was 0.25, while for respiratory sounds it was 2.50 and 0.45, respectively. When the presence of a sawtooth pattern and of respiratory sounds was combined, the LR of a positive test rose to 14.7 and the LR of a negative test was 0.42. CONCLUSIONS: A sawtooth pattern and/or respiratory sounds over the trachea are good indicators of retained secretions in patients receiving MV and may indicate the need for TS. Conversely, the absence of a sawtooth pattern may rule out retained secretions.

Bronchi↗
PubMed2000

Graded deletion and virus-induced activation of autoreactive CD4+ T cells.

We have examined factors governing the negative selection of autoreactive CD4(+) T cells in transgenic mice expressing low (HA12 mice) vs. high (HA104 mice) amounts of the influenza virus hemagglutinin (HA). When mated with TS1 mice that express a transgenic TCR specific for the I-Ed-restricted determinant site 1 (S1) of HA, thymocytes expressing high levels of the clonotypic TCR were deleted in both HA-transgenic lineages. However, through allelic inclusion, thymocytes with lower levels of the clonotypic TCR evaded deletion in TS1 x HA12 and TS1 x HA104 mice to graded degrees. Moreover, in both lineages, peripheral CD4(+) T cells could be activated by the S1 peptide in vitro, and by influenza virus in vivo. These findings indicate that allelic inclusion can allow autoreactive CD4(+) thymocytes to evade thymic deletion to varying extents reflecting variation in the expression of the self peptide, and can provide a basis for the activation of autoreactive peripheral T cells by viruses bearing homologues of self peptides ("molecular mimicry").

Adoptive Transfer↗
PubMed2003

CD25+ immunoregulatory CD4 T cells mediate acquired central transplantation tolerance.

Transplantation tolerance is induced reliably in experimental animals following intrathymic inoculation with the relevant donor strain Ags; however, the immunological mechanisms responsible for the induction and maintenance of the tolerant state remain unknown. We investigated these mechanisms using TCR transgenic mice (TS1) that carry T cells specific for an immunodominant, MHC class II-restricted peptide (S1) of the influenza PR8 hemagglutinin (HA) molecule. We demonstrated that TS1 mice reject skin grafts that have transgene-encoded HA molecules (HA104) as their sole antigenic disparity and that intrathymic but not i.v. inoculation of TS1 mice with S1 peptide induces tolerance to HA-expressing skin grafts. Intrathymic peptide inoculation was associated with a dose-dependent reduction in T cells bearing high levels of TCR specific for HA. However, this reduction was both incomplete and transient, with a full recovery of S1-specific thymocytes by 4 wk. Peptide inoculation into the thymus also resulted in the generation of immunoregulatory T cells (CD4+CD25+) that migrated to the peripheral lymphoid organs. Adoptive transfer experiments using FACS sorted CD4+CD25- and CD4+CD25+ T cells from tolerant mice revealed that the former but not the latter maintain the capacity to induce rejection of HA bearing skin allografts in syngeneic hosts. Our results suggest that both clonal frequency reduction in the thymus and immunoregulatory T cells exported from the thymus are critical to transplantation tolerance induced by intrathymic Ag inoculation.

Adoptive Transfer↗
PubMed2004

Increased mRNA expression of ADAMs in renal cell carcinoma and their association with clinical outcome.

ADAMs (a disintegrin and metalloproteinase) are cell-surface proteins with adhesion and protease activity which play important roles in many biological processes. Little is known about their role in cancer. The aim of the study was to assess the quantitative expression of the ADAMs in human renal cell carcinoma (RCC) and to associate expression levels with clinicopathological data. We investigated the mRNA expression of ADAM-8, -17, -19, -28, ADAM-TS1, and ADAM-TS2 in paired tissue samples from cancerous and non-cancerous parts of the kidneys of 27 patients with RCC who underwent tumour nephrectomy. Measurements were performed by means of the quantitative real-time RT-PCR on a LightCycler instrument. ADAM-8, -17, and -19 were significantly higher expressed (p<0.05 at least) in cancerous compared with the matched non-cancerous tissue in pT1 and > or =pT2 tumours, ADAM-28 and ADAM-TS2 only in pT1 tumours, and ADAM-TS1 was not differently expressed. All ADAMs except ADAM-TS1 showed an increase of expression in the non-cancerous tissue with rising pT stage suggesting an early involvement of ADAMs in the development of RCC. The expression of ADAM-8 was related to a shorter survival of patients and was the best predictor of distant metastases. Our results indicate a potential role for ADAMs in RCC and that the overexpression might be a useful predictive tool.

Aged↗
PubMed1986

The differential ability of splenic adherent cells from B6.lpr mice to induce suppressor T cells.

Hapten-coupled splenic adherent cells or resident peritoneal cells from autoimmune B6.lpr mice that are over 5 mo of age fail to induce first-order inducer suppressor T cells (Ts1). However, the same population of hapten-coupled cells can induce both delayed-type hypersensitivity responses and third-order effector suppressor T cells (Ts3). Thus, splenic and peritoneal antigen-presenting cells from B6.lpr mice display a defined defect in the ability to induce certain suppressor T cell responses. The cellular defect in Ts1 induction is controlled by the lpr gene, since age-matched congenic B6 mice do not display this defect. The splenic adherent cell defect is temporarily correlated with the autoimmunity that develops in B6.lpr animals. The antigen-presenting defect in the B6.lpr splenic adherent population for Ts1 induction is reversible by culturing the cells in interferon-gamma. The results are discussed as an illustration of the relationship between experimental models of autoimmunity and defects in a suppressor T cell cascade.

Aging↗
PubMed1986

Monoclonal antibodies to thromboxane synthase from porcine lung. Production and application to development of a tandem immunoradiometric assay.

Two hybridoma cell lines secreting antibodies against thromboxane synthase of porcine lung were produced. Clone TS1 secretes IgG2a antibody of lower affinity, while clone TS2 secretes IgG1 antibody of higher affinity. Both antibodies (when bound to rabbit anti-mouse IgG-Staphylococcus aureus complex) can immunoprecipitate thromboxane synthase from crude enzyme preparations in an active form suggesting that binding was not directed at the active site. Each antibody showed a distinctive pattern of cross-reactivity with thromboxane synthase from different porcine tissues. Neither of the antibodies cross-reacted with the enzyme from tissues of other species tested, indicating the heterogeneous nature of the enzyme among species. Competitive binding assay revealed that TS1 and TS2 recognized different determinants on the enzyme. The fact that two antibodies bind to separate epitopes on the same enzyme allows the development of a sensitive tandem immunoradiometric assay. The assay, based on binding of 125I-TS2 to thromboxane synthase immobilized on TS1-S. aureus complex, was linear with 7.5 approximately 75 ng of purified lung thromboxane synthase as standards and applicable to enzyme preparations regardless of their purity. The concentration of immunoreactive thromboxane synthase in porcine tissues as determined by this assay followed the order of platelet greater than colon greater than duodenum greater than lung greater than kidney greater than stomach. The fact that gastrointestinal tract is enriched with thromboxane synthase suggests that thromboxane may have significant physiological roles to be recognized in these organs.

Animals↗
PubMed1986

Noninflammatory spongiform polioencephalomyelopathy caused by a neurotropic temperature-sensitive mutant of Moloney murine leukemia virus TB.

Newborn inbred CFW/D mice were inoculated intraperitoneally with ts1, a neurotropic temperature-sensitive mutant of Moloney murine leukemia virus TB (MoMuLV-TB), with the parental wild type (wt) MoMuLV-TB, or with culture medium. A progressive symmetric hindlimb paresis that progressed to paralysis was observed in ts1-infected mice. Wt-infected mice and control mice had no neurologic signs. The severity and progression of neurologic signs correlated with the location, development, and progression of lesions. Lesions consisted of neuronal and glial cell vacuolization in the brain and the anterior horn of the spinal cord, spongiform change in the associated neuropil, spongiform change in lateral and ventral funiculi, and late fibrillary gliosis in the brainstem. There was no inflammation. Lesions were symmetric, increased in severity with time, and consistently arose at specific times in specific nuclei and areas of the brain and spinal cord. Similar, but less severe, histologic lesions were observed in corresponding areas of the central nervous system from wt-infected mice. Ultrastructurally, neuronal and glial cell vacuolization in ts1-infected mice at 31 days after inoculation was caused by dilatation of the endoplasmic reticulum and Golgi complex. Virions were observed in extremely low numbers predominantly in extracellular space and budding from membranes of neurons and glial cells. Virions were not observed in the endoplasmic reticulum or Golgi complex of neurons, nor were there cytoplasmic vacuoles that contained abnormal virions.

Animals↗
PubMed1980

Antigen and receptor-driven regulatory mechanisms. VI. Demonstration of cross-reactive idiotypic determinants on azobenzenearsonate-specific antigen-binding suppressor T cells producing soluble suppressor factor(s).

The first detectable suppressor T cell (Ts) arising after i.v. administration of azobenzenearsonate- (ABA) conjugated syngeneic spleen cells to A/J mice has been studied for its receptor specificity and ability to produce soluble suppressor factor(s). This cell, termed Ts1, has a specific receptor for the eliciting antigen ABA, as demonstrated by selective binding to ABA protein- but not TNP protein-coated plastic dishes. The activity of ABA-Ts1 can be abrogated by treatment with anti-idiotypic antibodies made against anti-ABA antibodies of A/J mice (anti-CRI), indicating that these ABA-binding cells possess a surface receptor structure sharing idiotypic determinants with antibodies of the same specificity. Finally, soluble extracts from, antigen-adherent ABA-Ts1, but not nonadherent cells from the same spleen cell population, possess suppressive activity when assayed directly for afferent suppression or tested for their ability to trigger a second population of Ts (Ts2) in naive recipients. These findings demonstrate a close concordance between a T cell surface receptor, soluble T suppressor factors, and B cell derived antibody, all capable of direct recognition of the eliciting ABA antigen.

Animals↗
PubMed1982

In vivo role of macrophages in transmission of dengue virus-induced suppressor signal to T lymphocytes.

Dengue type 2 virus (DV)-induced suppressor T cells (Ts1) produce a soluble suppressor factor (SF) which stimulates a subpopulation of T lymphocytes (Ts2) to produce prostaglandin which suppresses DV-specific IgM antibody plaque forming cells (PFC) in vivo and in vitro. The present study was undertaken to investigate the intermediary role of macrophages in transmission of signal from Ts1 to Ts2. The SF is adsorbed on live or heat-killed mouse peritoneal macrophages and transmits DV-specific PFC in spleen after i.p. or i.v. inoculation in DV-primed mice. The suppression is antigen-specific. SF or SF-adsorbed heat-killed macrophages failed to transmit suppression in silica-treated macrophage-depleted mice when injected i.p., while SF-adsorbed live macrophages could transmit suppression. In macrophage-depleted mice suppression could be transmitted by SF-adsorbed heat-killed macrophages on i.v. inoculation. It was therefore concluded that live macrophage-killed cells are also essential for transmission of suppressor signal by SF from Ts1 to Ts2 in vivo.

Animals↗
PubMed1984

Prevention of granuloma development in the mouse by using T cell hybridoma products.

The ability of an azobenzenearsonate (ABA)-specific suppressor T cell factor, a soluble extract from first order suppressor T cells (Ts1), and suppressor molecules produced by a long-term T cell hybridoma to regulate ABA-specific granuloma formation was studied. ABA-derivatized syngeneic spleen cells (ABA-SC) administered subcutaneously induced persistent delayed-type hypersensitivity (DTH) responses, detected by footpad swelling and hapten-specific granuloma formation by 72 and 96 hr after challenge with ABA-bovine serum albumin coupled to polyacrylamide beads (ABA-BSA-PAB). Soluble factors from ABA-specific Ts1 prevented DTH and granulomatous development after subcutaneous administration of ABA-SC. Moreover, the in vivo administration of a factor that is derived from a Ts1 functioning hybrid cell line induced a second set of suppressor cells (Ts2) that upon transfer to syngeneic ABA-primed mice were able to inhibit granuloma formation in the footpad, as well as in the gastrointestinal tract after challenge with ABA-BSA-PAB. These experiments demonstrate the dependence of the granulomatous reaction on T cell-mediated events, as well as the potential therapeutic efficacy of an antigen-specific suppressor T cell factor and a hybridoma T cell product in limiting antigen-specific granuloma formation in vivo.

Animals↗
PubMedDate not supplied

Hypercapnia-induced thermoregulatory disturbances in rabbits at low ambient temperature.

The effect of 30 minute inhalation of a gaseous mixture containing 6% CO2, 21% O2 and 73 N2 on the thermoregulatory reactions was studied in rabbits at ambient temperatures (Ta) of 6 and 18 degrees C. At Ta 6 degrees C the CO2 inhalation caused a greater fall of the rectal temperature (Tre) as well as the subcutaneous and skin temperatures (TS1 and TS2) than at Ta 18 degrees C. At the same time, the gradients Tre-TS1 and TS1-TS2 decreased, the respiratory rate increased and the electrical activity of skeletal muscles was depressed in both thermal conditions. A considerable fall in heat production occurred only at Ta 6 degrees C, at which the initial electric activity of the skeletal muscles was also greater. These results suggest that Tre fall associated with CO2 inhalation at low temperatures was caused mainly by inhibition of shivering-thermogenesis, however, the changes in skin temperatures were without any greater importance for the body temperature at Ta 6 degrees C as well as at 18 degrees C.

Aerosols↗
PubMed1995

Use of anticytokeratin monoclonal anti-idiotypic antibodies to improve tumor:nontumor ratio in experimental radioimmunolocalization.

A syngeneic, high-affinity, anti-idiotypic monoclonal antibody (MAb; alpha TS1) raised against an anticytokeratin monoclonal antibody (TS1) was evaluated as a second antibody to promote the rapid clearance of radiolabeled TS1 from the blood during experimental radioimmunolocalization. By using a novel biosensor technology (BIAcore), association rate dissociation rate, and affinity constants between the idiotype and the anti-idiotype could be determined. The in vivo results in nude mice carrying HeLa Hep 2 tumors demonstrate the possibility of selectively regulating the amount of the idiotypic 125I-labeled circulating MAb by in vivo injection of this high-affinity, anti-idiotypic antibody. Injection of the anti-idiotype in a molar ratio of 0.75 to the idiotype cleared the blood pool from circulating radiolabeled idiotype within 24 h, with a concomitant rapid excretion of 125I in urine. The total amount of remaining radioactivity in the animals decreased to 15-20% during these 24 h, with the tumors still retaining 60-65% of their initial radioactivity. This approach, using syngeneic primary and secondary MAbs with minimized immunogenicity, significantly improves the tumor:nontumor ratio, thus improving efficiency in experimental radioimmunolocalization and radioimmunotherapy, leaving the endogenous antibody repertoire of the host unaffected.

Animals↗