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Biomedical subjects

N S Liao

Publications and source records attributed to N S Liao.

At least 19 recordsLinked to original sources
PubMed2001

Protection against lethal enterovirus 71 infection in newborn mice by passive immunization with subunit VP1 vaccines and inactivated virus.

Enterovirus 71 (EV71), the newest member of Enteroviridae, is notable for its etiological role in epidemics of severe neurological diseases in children. Developing effective vaccines is considered a top choice among all control measures. We compared the inactivated virus vaccine (10 microg protein/mouse) with subunit vaccines--VP1 DNA vaccine (100 microg/mouse) or recombinant VP1 protein (10 microg/mouse)--in its ability to elicit maternal antibody and to provide protection against lethal infection of EV71 in suckling mice. Prior to gestation, all three groups of vaccinated dams possessed similar levels of neutralizing antibody. With a challenge dose of 2300 LD(50) virus/mouse, suckling mice born to dams immunized with inactivated virus showed 80% survival. The subunit vaccines provided protection only at a lower challenge dosage of 230 LD(50) per mouse, with 40% survival for DNA vaccine and 80% survival for VP1 protein. The cytokine profile produced by splenocytes showed a high level of IL-4 in the inactivated virus group, high levels of IFN-gamma and IL-12 in the DNA vaccine group, and high levels of IL-10 and IFN-gamma in the VP1 protein group. Overall, the inactivated virus elicited a much greater magnitude of immune response than the subunit vaccines, including total IgG, all four IgG subtypes, and T-helper-cell responses; these antibodies were shown to be protective against lethal infection when passively transferred to susceptible newborn mice. Our data indicated that inactivated virus is the choice of vaccine preparation capable of fulfilling the demand for effective control, and that VP1 subunit vaccines remain promising vaccine strategies that require further refinement.

Animals↗
PubMed1999

IL-15 promotes survival but not effector function differentiation of CD8+ TCRalphabeta+ intestinal intraepithelial lymphocytes.

CD8 single-positive cells, including CD8alphaalpha+ and CD8alphabeta+ subsets, constitute the majority of TCRalphabeta+ intestinal intraepithelial lymphocytes (alphabeta iIEL) in mice. CD8+ alphabeta iIEL show significantly weaker responses to TCR stimulation in the presence of exogenous IL-2 than do CD8+ T cells of the central immune system. IL-15 is a T cell growth factor likely expressed in the intestine mucosa. To understand the role of IL-15 in CD8+ alphabeta iIEL biology, we compared the effects of exogenous IL-15 and IL-2 on the survival and primary responses of the two CD8+ alphabeta iIEL subsets in vitro. In contrast to the death of approximately 60% of both CD8alphaalpha+ and CD8alphabeta+ iIEL cultured in IL-2 with or without TCR stimulation, IL-15 promoted survival of the CD8alphaalpha+ subset in the presence of TCR stimulation and promoted survival of both subsets in the absence of TCR stimulation. The higher proliferation level of TCR stimulated CD8alphaalpha+ alphabeta iIEL cultured in IL-15 compared with those cultured in IL-2 is likely due to IL-15's prosurvival effects. In addition, unlike exogenous IL-2, exogenous IL-15 did not support the effector functions of either iIEL subsets, including IFN-gamma production, IL-4-induced Th2 cytokine production, and anti-TCR mAb-redirected cytotoxicity. These findings demonstrate that IL-15 and IL-2 are functionally distinct and suggest that IL-15 plays a unique role in the maintenance of the CD8+ alphabeta iIEL pool in the absence of Ag stimulation and in the survival and expansion of CD8alphaalpha+ alphabeta iIEL upon Ag stimulation.

Animals↗
PubMed1999

Differential effects of IL-2 and IL-15 on the death and survival of activated TCR gamma delta+ intestinal intraepithelial lymphocytes.

TCR gamma delta+ cells are enriched in the intestine mucosa and constitute approximately half of the intestinal intraepithelial lymphocytes (iIEL) in mice. They are likely activated by self and foreign Ags in situ, but little is known about how the activated gamma delta iIEL are regulated. In the iIEL compartment, IL-2 is produced by activated TCR alpha beta+ iIEL, and IL-15 message is detected in iIEL and in the epithelial cells. We found surface expression of IL-2 as well as IL-15Rs on activated gamma delta iIEL, and examined the effects of IL-2 and IL-15 on the survival and death of gamma delta iIEL during secondary stimulation through TCR. We found that both cytokines supported growth of the restimulated gamma delta iIEL, but exerted different effects on their survival. A significant higher number of live cells were recovered from the gamma delta iIEL cultures restimulated in IL-15 than in IL-2. Quantitation of apoptotic cells showed more cell death in the IL-2 group than in the IL-15 group. The cell death was associated with restimulation through TCR and was not caused by insufficient growth factor, thus representing activation-induced cell death. Western blot analyses found no difference in the levels of Bcl-2 and Bax proteins between the two groups. However, the level of Bcl-xL protein diminished with time in the IL-2 group whereas the level was sustained in the IL-15 group, which may contribute to the pro-survival effect of IL-15. These results demonstrated that the survival of activated gamma delta iIEL is differentially regulated by IL-2 and IL-15.

Animals↗
PubMed1996

Activated alpha beta-CD8+, but not alpha alpha-CD8+, TCR-alpha beta+ murine intestinal intraepithelial lymphocytes can mediate perforin-based cytotoxicity, whereas both subsets are active in Fas-based cytotoxicity.

CD8 single-positive (CD8+) T cells in murine intestinal intraepithelial lymphocytes (iIEL) consist of alpha alpha-CD8+ and alpha beta-CD8+ subpopulations. Cytotoxicity represents an important function of peripheral CD8+ T cells, so we examined perforin-granzymebased and Fas-based cytotoxicity of activated CD8+ TCR-alpha beta+ iIEL subsets. We found that allospecific CTL activity was induced from alpha beta-CD8+ iIEL but not from alpha alpha-CD8+ iIEL even when allospecific TCR were present on the iIEL, as demonstrated by using 2C TCR transgenic mice. On the other hand, both CD8+ iIEL subsets proliferated upon allostimulation with a lower responder frequency than CD8+ LN cells. The alpha alpha-CD8+ TCR-alpha beta+ iIEL appeared to lose their ability to perform perforin-based killing after activation through TCR because fresh cells lysed P815 cells coated with anti-TCR beta-chain (TCR-beta) mAb, whereas cells activated by plate-bound anti-TCR mAb did not. Of interest, both activated CD8+ TCR-alpha beta+ iIEL subsets, but not fresh cells, were able to mediate Fas-based killing when triggered with PMA and CA2+ ionophore.

Animals↗
PubMed1995

Differential requirement of CD28 costimulation for activation of murine CD8+ intestinal intraepithelial lymphocyte subsets and lymph node cells.

The CD8+CD4- (CD8+) murine small intestinal intraepithelial lymphocytes (IELs) contain two subpopulations, one expressing alpha alpha-CD8 homodimers and another alpha beta-CD8 heterodimers. In this study, plate-bound anti-TCR beta-chain (TCR-beta) mAb alone or combined with anti-CD28 mAb is used as a model system to study activation requirement of these two CD8+ IEL subsets. In contrast to CD8+ lymph node (LN) cells that require both TCR and CD28 triggering for activation, alpha beta-CD8+ IELs proliferate and produce IL-2 and IFN-gamma when stimulated with anti-TCR-beta mAb alone, and soluble CTLA-4 Ig has no effect on their responses. On the other hand, alpha alpha-CD8+ IELs neither make IL-2 or IFN-gamma nor proliferate even when both stimuli are provided. However, alpha alpha-CD8+ IELs are capable of proliferation in both CD8+ IEL subsets is lower than in CD8+ LN cells, which contributes to the weaker and delayed response of CD8+ IELs.

Animals↗
PubMed1992

Expression of the Mls-1a superantigen results in an increased frequency of V beta 14+ T cells.

Minor lymphocyte-stimulating (Mls) Ag are alloantigens that stimulate T cells expressing specific V beta regions. Recent studies have established that Mls Ag are examples of endogenous superantigens encoded by the products of endogenous mouse mammary tumor virus (MLV) genomes. In a mouse strain that expresses a given mammary tumor virus (Mls) Ag, reactive T cells expressing the corresponding V beta region are profoundly deficient, due at least in part to clonal deletion of the cells during their development. Expression of Mls and other endogenous superantigens, therefore, results in profound alterations in the ultimate repertoire of T cells in an animal. A role for endogenous superantigens in positive selection of T cells has not been previously established. Here we present evidence that expression of Mls-1a leads to a specific increase in the abundance of V beta 14+ T cells. Genetic studies indicate linkage of the effect to the Mls-1a gene. Neonatal tolerance studies argue against the possibility that the increase is due solely to the deletion of Mls-reactive V beta 14- T cells. The results are consistent with the Mls-1a product playing a role in the positive selection of V beta 14+ T cells.

Animals↗
PubMed1992

Most gamma delta T cells develop normally in beta 2-microglobulin-deficient mice.

The specificity of T cells bearing gamma delta T-cell receptors (gamma delta+ T cells) is poorly characterized. Earlier studies suggest that like alpha beta+CD8+ T cells, some gamma delta+ T cells may recognize antigens associated with class I major histocompatibility complex molecules. alpha beta+CD8+ T cells are nearly absent in class I-deficient mice (mutant for beta 2-microglobulin), reflecting a requirement for intrathymic "positive selection" of these cells by class I molecules. Here, we examine whether the development of gamma delta+ T cells is altered in the beta 2-microglobulin mutant mice. We show that the cellularity, marker expression, repertoire, and functional competence of gamma delta+ T cells are not detectably deficient in beta 2-microglobulin mutant mice. We conclude that class I expression is unnecessary for the development of most gamma delta+ T cells.

Animals↗
PubMed1991

MHC class I deficiency: susceptibility to natural killer (NK) cells and impaired NK activity.

The role of major histocompatibility complex (MHC) class I expression in natural killer (NK) cell target recognition is controversial. Normal T cell blasts from MHC class I-deficient mutant mice were found to serve as target cells for NK cells in vitro, which suggests that MHC class I molecules are directly involved in NK cell recognition. Spleen cells from the mutant mice were deficient in their ability to lyse MHC class I-deficient target cells or NK-susceptible tumor targets, and mutant mice could not reject allogeneic bone marrow. Thus, class I molecules may participate in the positive selection or tolerance induction of NK cells.

Animals↗
PubMed1991

Rejection of class I MHC-deficient haemopoietic cells by irradiated MHC-matched mice.

Irradiated MHC-heterozygous mice often reject bone marrow cells transplanted from one of the homozygous parental strains, a phenomenon ('hybrid resistance') that appears to violate the laws of transplantation. Rejection of parental and allogeneic marrow cells also differs from conventional T cell-mediated rejection mechanisms as it is effected by NK1.1+ cells. To account for the unusual specificity of bone marrow rejection, it has been proposed that NK1.1+ cells destroy marrow cells that fail to express the full complement of self MHC class I (MHC-I) molecules. We show here that NK1.1+ cells in normal mice reject haemopoietic transplants from mice that are deficient for normal cell-surface MHC-I expression because of a targeted mutation in the beta 2-microglobulin gene. These findings demonstrate that deficient expression of MHC-I molecules renders marrow cells susceptible to rejection.

Animals↗
PubMed1990

Expression of the V beta 5.1 gene by murine peripheral T cells is controlled by MHC genes and skewed to the CD8+ subset.

We have examined the usage of the V beta 5.1 region in peripheral T cell populations of several mouse strains by measuring V beta 5.1 transcript levels. The results show that V beta 5.1 is expressed predominantly by CD8+ T cells in mice of several MHC haplotypes. This finding suggests that V beta 5.1 may confer restriction to class 1 molecules present in these strains. Interestingly, however, T cells expressing V beta 5.1, like those expressing V beta 17a and V beta 11, are clonally deleted from both CD4 and CD8 subsets in mice that express MHC IE molecules. The latter result implies that V beta 5.1 confers reactivity to a class 2 molecule (IE). These results are discussed in terms of positive selection and clonal deletion. Finally we provide evidence that genes in the K or A regions of the MHC also control V beta 5.1 usage.

Animals↗
PubMed1990

Selective expression of V delta 6 genes by B2A2- CD4- CD8- T cell receptor gamma/delta thymocytes.

Most CD4-CD8- adult murine thymocytes characterized by absence of the B2A2 (J11d) antigen express T cell receptors (TcR) alpha/beta and utilize preferentially V beta 8.2 segments. To a much lesser extent, B2A2-CD4-CD8- thymocytes also express TcR gamma/delta, as evidenced by biochemical and Northern blot analysis. We have now been able to exclude the possibility that these cells might co-express both types of TcR: V beta 8+ B2A2- CD4-CD8- thymocytes expressed no TcR delta mRNA whereas the corresponding V beta 8- subset transcribed full-length TcR gamma as well as delta mRNA. Furthermore, the TcR gamma/delta expressing B2A2- thymocytes were found to use preferentially V delta 6 genes. Conversely, they did not express V delta 5 genes which are most frequently used by other TcR gamma/delta-bearing populations such as B2A2+ CD4-CD8- thymocytes or CD4-CD8- peripheral lymph node cells. RNase protection experiments showed that two particular V delta 6 transcripts predominate in these gamma/delta populations, the most prominent V delta 6 sequence being highly homologous if not identical to V alpha 7.1. Our observations extend previous information on overlapping V alpha and V delta gene repertoires, particularly in the cross-hybridizing V alpha 7/V delta 6 gene family. Moreover, our data suggest that B2A2-CD4-CD8- thymocytes represent a developmentally unique subset in which both V delta and V beta segments are nonrandomly expressed.

Animals↗
PubMed1989

Positive selection determines T cell receptor V beta 14 gene usage by CD8+ T cells.

We report here a mAb, 14-2, reactive with TCRs that include V beta 14. The frequency of V beta 14+ T cells varies with CD4 and CD8 subset and is controlled by the H-2 genes. Thus CD8+ T cells from H-2b mice include approximately 2.3% V beta 14+ T cells while CD8+ T cells from mice expressing K kappa include greater than 8% V beta 14+ T cells. In all strains examined, 7-8% of CD4+ T cells express V beta 14. The frequent usage of V beta 14 in CD8+ T cells of K kappa-expressing mice is a result of preferential positive selection of V beta 14+ CD8+ T cells as demonstrated by analysis of radiation chimeras. These studies demonstrate that H-2-dependent positive selection occurs in unmanipulated mice. Furthermore, the results imply that positive selection, and possibly H-2 restriction, can be strongly influenced by a V beta domain, with some independence from the beta-junctional sequence and alpha chain.

Animals↗
PubMed1989

Adhesion of lymphoid cells to the carboxyl-terminal heparin-binding domains of fibronectin.

Previously, we have shown that some lymphoid cell lines adhere to fibronectin (FN)-coated substratum, whereas others do not. In this study, the adhesion of five adherent lymphoid cell lines to different FN domains was examined. These cell lines ranged in their adherence to substratum coated with FN, the cell-binding domain (CBD) fragment, or the heparin-binding domain (HBD) fragments. None of the cell lines adhered to substratum coated with the gelatin-binding domain fragment. Three of the lymphoid cell lines adhered preferentially to HBD over CBD, whereas two other lymphoid cell lines and BHK fibroblasts adhered preferentially to CBD. These results suggest that two distinct adhesive interactions occur between cells and FN and that the pattern of interaction varies among cell types. Using MOPC 315 (which adheres preferentially to HBD) as a cell model to study the cell-HBD interaction, the HBD-promoted adhesion was found to be independent of the RGD sequence and could be inhibited by anti-FN antibodies. Moreover, the MOPC 315-HBD interaction had the following characteristics: (1) adhesion was temperature dependent, (2) presence of divalent cations was necessary, (3) integrity of cellular microfilaments but not microtubules was required, (4) inhibition of protein synthesis abolished adhesion, (5) pretreatment of cells with trypsin inhibited adhesion, and (6) the adhesion was mediated by the carboxyl-terminal HBD.

Cell Adhesion↗
PubMed1987

Aging and lymphocyte cytoskeleton: age-related decline in the state of actin polymerization in T lymphocytes from Fischer F344 rats.

T cell functions are known to decline with age, but the underlying cause of the decline is unclear. Because of the importance of cytoskeletal elements in cellular functions, we examined the content and the state of polymerization of actin in lymphocytes from Fischer F344 rats of four different ages (6, 14, 23, and 31 mo). The cellular actin content was determined by a DNAase I inhibition assay. Our results indicate that the total actin content of spleen lymphocytes did not change significantly with age; however, polymeric actin content, particularly in T cells, decreased with age, which might be a result of the shift from the polymeric actin pool to the monomeric pool. Similar changes also occurred in B cells but to a lesser extent. We conclude that the state of polymerization of lymphocytes changed drastically with age, and that this might be an important factor in the age-related decline in the cellular functions of lymphocytes.

Actins↗
PubMed1987

Adhesion of lymphoid cell lines to fibronectin-coated substratum: biochemical and physiological characterization and the identification of a 140-kDa fibronectin receptor.

Little information is available on the interaction between lymphocytes and fibronectin (fn). To gain a better understanding on this issue we examined the adhesion of 12 lymphoid cell lines, each exhibiting different phenotypic characteristics, to fn-coated substratum. Of the cell lines tested, five that adhered to fn possessed B-cell characteristics, while neither the T-cell lines nor the pre-B-cell line adhered. The physiology and biochemistry of adhesion of a B-cell line, MOPC 315, were examined in detail. Our results indicated that (1) the adhesion was a specific and time-dependent process, (2) the adhesion was temperature-dependent and inhibited by metabolic inhibitors, such as KCN and 2-deoxyglucose, (3) the presence of cycloheximide and pretreatment of cells with trypsin inhibited adhesion, (4) a 140-kDa surface protein was immunoprecipitated by anti-fn receptor antibodies, (5) the presence of divalent cations was essential for adhesion, (6) the presence of colchicine had no effect on adhesion, while cytochalasin B partially inhibited adhesion, and (7) the treatment of cells by both phorbol 12-myristate 13-acetate and calcium ionophore A23187 enhanced adhesion. In this study, we have established the interaction between lymphoid cell lines and fn. Such an interaction might play an important role in the behavior of lymphocytes in tissues.

Animals↗