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Biomedical subjects

D F Tough

Publications and source records attributed to D F Tough.

30 records · Page 2Linked to original sources
PubMed1996

In vivo response of mature T cells to Mlsa antigens. Long-term progeny of dividing cells include cells with a naive phenotype.

To characterize T cells surviving elimination following strong in vivo responses, bromodeoxyuridine (BrdU) was used to mark the V beta 6+ CD4+ T cells proliferating after exposure to MLsa superantigens. Though a portion of the surviving V beta 6+ cells failed to label with BrdU, many were BrdU+, indicating that some proliferating cells escape elimination. Both the portion of V beta 6+ cells responding to MLs Ag in vivo and the number of responding cells that escaped elimination were influenced by the MHC haplotype; weaker responses correlated with enhanced survival of BrdU+ V beta 6+ cells. As expected, some of these cells expressed cell surface markers generally associated with an activated/memory phenotype. Significantly, however, a large proportion of BrdU+ V beta 6+ cells were phenotypically indistinguishable from naive cells.

Animals↗
PubMed1995

Life span of naive and memory T cells.

The life span of mature T cells is reviewed. Peripheral T lymphocytes are a heterogeneous population and comprise a mixture of naive, effector and memory cells. The recirculating pool of mature T cells is formed during young life through gradual release of naive T cells from the thymus. In adults, the pool of mature T cells is relatively self-sufficient, and input of new T cells from the thymus declines to low levels. Studies on T cell turnover indicate that most peripheral T cells can remain in a resting state for long periods (months in rodents and years in humans). Examination of the phenotype of dividing versus nondividing cells suggests that typical naive T cells are long-lived resting cells whereas the majority of effector and memory T cells have a much more rapid turnover. However, some memory T cells appear to divide very infrequently and eventually return to a resting state. The factors controlling the generation and maintenance of memory T cells are discussed.

Animals↗
PubMed1995

Lifespan of lymphocytes.

T and B lymphocytes comprise heterogeneous populations of cells at various stages of differentiation and activation. T- and B-cell subsets have different roles in the maintenance of immune homeostasis, and their functional differences are reflected by their respective lifespans. This review briefly summarizes the available data on lymphocyte lifespan, including the kinetics of T- and B-cell development in the primary lymphoid organs and the proliferative behavior of naive, effector and memory lymphocytes in the peripheral lymphoid compartment.

Animals↗
PubMed1994

Lymphocyte life-span and memory.

Differentiation of immature T and B cells in the primary lymphoid organs gives rise to a pool of long-lived lymphocytes that recirculate through the secondary lymphoid tissues. On the basis of their surface markers, T and B cells comprise a mixture of naïve and memory cells with differing life-spans. Immunization (and vaccination) causes naïve lymphocytes to proliferate and differentiate into effector cells and memory cells. Whether the survival of memory cells is innate or requires persistent contact with residual antigen is controversial. Resolving this issue may be crucial for designing optimal vaccines.

Animals↗
PubMed1994

Turnover of naive- and memory-phenotype T cells.

On the basis of their surface markers, T lymphocytes are divided into subsets of "naive" and "memory cells". We have defined the interrelationship and relative life spans of naive and memory T cells by examining the surface markers on murine T cells incorporating bromodeoxyuridine, a DNA precursor, given in the drinking water. Three findings are reported. First, using a new method we show that the release of newly formed naive T cells from the unmanipulated thymus is very low (confirming the findings of others with surgical approaches). Second, in thymectomized mice, T cells with a naive phenotype remain in interphase for prolonged periods; however, some of these cells divide and retain (or regain) their "naive" markers. Third, most T cells with a memory phenotype divide rapidly, but others remain in interphase for many weeks. Collectively, the data indicate that long-lived T cells have multiple phenotypes and contain a mixture of memory cells, naive (virgin) cells, and memory cells masquerading as naive cells.

Administration, Oral↗
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

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↗
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↗
PubMed1986

Regulation of 3-hydroxy-3-methylglutaryl coenzyme A reductase and lipid metabolism in a concanavalin A-resistant Chinese hamster ovary cell line.

Lipid metabolism in a concanavalin A-resistant, glycosylation-defective mutant cell line was investigated by comparing growth properties, lipid composition, and lipid biosynthesis in wild-type (WT), mutant (CR-7), and revertant (RCR-7) cells. In contrast to WT and RCR-7, the mutant was auxotrophic for cholesterol, but mevalonolactone did not restore growth on lipoprotein-deficient medium. The use of R-[2-14C]mevalonolactone revealed that CR-7 was deficient in the conversion of lanosterol to cholesterol. Total lipid and phospholipid content and composition were similar in all three cell lines, but CR-7 displayed subnormal content and biosynthesis of cholesterol and unsaturated fatty acids. The mutant was hypersensitive to compactin and was unable to upregulate either 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity or the binding and internalization of 125I-labeled low-density lipoprotein (LDL) in response to lipoprotein deprivation. HMG-CoA reductase activity in all three cell lines showed similar kinetics and phosphorylation status, and the binding kinetics and degradation of 125I-LDL were also similar, suggesting that CR-7 possesses kinetically normal reductase and LDL binding sites, but is deficient in their coordinate regulation. Tunicamycin (1-2 micrograms/ml) strongly and reversibly suppressed reductase activity in WT and RCR-7. CR-7 was resistant to this inhibitor. In WT cells this suppressive effect was accompanied by inhibition of 3H-labeled mannose incorporation into cellular protein, but 3H-labeled leucine incorporation was unaffected. Immunotitration of HMG-CoA reductase activity in extracts of WT cells, cultured in the presence and absence of tunicamycin, showed that suppression of reductase activity reflected the presence of reduced amounts of reductase protein, implying that glycosylation plays an important role in the coordinate regulation of HMG-CoA reductase activity and LDL binding.

Acetates↗
PubMedDate not supplied

p21ras independent down-regulation of ras-induced increases in natural antibody binding during tumor progression.

Selective outgrowth of v-H-ras-infected 10T1/2 cells based on the cointroduction of a gene for resistance to geneticin (G418), yielded cells which exhibited an increased capacity to bind polyclonal serum natural antibody (NAb). This demonstrated an NAb-susceptible phase of tumor development which would be a basic requirement for NAb-mediated surveillance of tumors. The ras-oncogene dependence of the high-NAb-binding phenotype provided a model for assessing NAb resistance against ras transformants in vivo and for a comparative analysis of phenotypic and genetic alterations contributing to the progression of ras transformants. Variants were developed through in vitro and in vivo models of tumor progression. T24-H-ras and v-H-ras transformants were isolated in vitro through more rigorous growth conditions, focus formation in the presence of untransformed cells with no selecting drug. These clones expressed p21ras but exhibited little or no increase in NAb binding. Variants recovered following growth from intravenous or threshold subcutaneous (s.c.) inocula of high-NAb-binding ras transformants in syngeneic C3H/HeN mice exhibited decreases in NAb binding but no uniform change in p21ras. Concurring inverse correlations between NAb binding and s.c. tumorigenicity were exhibited by the T24-H-ras transformant clones, the ras transformants grown in vivo, and the v-H-ras-transformed clones isolated in the presence versus the absence of untransformed cells. This consistent inverse correlation, together with the reduced NAb binding of the ras transformants grown in vivo, provides strong evidence that NAb participates in the defense against ras-transformed cells in vivo. The lack of any direct correlation between p21ras expression and the reduction in NAb binding or the increase in tumorigenicity of cells generated through progression in vivo suggested the regulatory action of additional genes. Hybridization studies between high- and low-NAb-binding clones implicated the activation of an additional oncogene and inactivation of an antioncogene in the down-regulation of the ras-induced increases in NAb binding associated with tumor progression.

Animals↗