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N A Williams

Publications and source records attributed to N A Williams.

At least 55 records · Page 3Linked to original sources
PubMed1996

The role of small intestinal antigen-presenting cells in the induction of T-cell reactivity to soluble protein antigens: association between aberrant presentation in the lamina propria and oral tolerance.

The oral administration of soluble protein antigen results in profound immunological tolerance. However, the tissue location and function of antigen-presenting cells (APC) that stimulate this response remain unclear. We have hypothesized that the properties of cells presenting antigen to naive T cells within the gut are involved, and therefore gut APC should stimulate T-cell responses with different characteristics to those induced by other APC. To test this, we studied in vitro primary T-cell responses following presentation of soluble protein antigen by cells from the Peyer's patches (PPC) and lamina propria (LPC) of the murine small intestine and the spleen (SPLC). Each APC population stimulated antigen-specific proliferative responses with similar anamnestic characteristics; however, analysis of the cytokines produced revealed marked differences. Whereas SPLC stimulated the balanced production of T-helper type 1 (Th1) and Th2 cytokines, PPC induced a profile consistent with the provision of T-cell help for IgA production. Interestingly, presentation of antigen by LPC stimulated high levels of interferon-gamma (IFN-gamma) and transforming growth factor-beta (TGF-beta) in the absence of other cytokines [interleukin-2 (IL-2), IL-4, IL-5]. Evidence from analysis of cell activation and division within the cultures suggested that this profile may result from the preferential activation of CD8+ T cells by LPC; however, the lack of conventional CD4+ T-cell cytokines indicated a defect in the normal function of these cells. Adoptive transfer of antigen-pulsed LPC to syngeneic animals abrogated the induction of delayed-type hypersensitivity (DTH) responsiveness, which followed a subsequent conventional antigen challenge further suggesting a role for lamina propria APC in tolerance induction.

Animals↗
PubMed1996

Cross-linking of cell surface ganglioside GM1 induces the selective apoptosis of mature CD8+ T lymphocytes.

Gangliosides are glycosphingolipids found ubiquitously on the surface of mammalian cells. They contain a ceramide tail that is inserted into the membrane and exposed carbohydrate and sialic acid moieties. The non-toxic B subunit oligomer (EtxB) of Escherichia coli heat-labile enterotoxin (Etx) is a potent immunogen in vivo and has profound modulatory effects on EtxB-primed lymphocytes in vitro, properties which are dependent on its ability to bind to GM1 ganglioside receptors. Here, it is shown that cross-linking GM1 by EtxB causes a differential effect on mature CD4(+) and CD8(+) T cells from lymph node cultures proliferating in response to an unrelated antigen, ovalbumin. Addition of EtxB to such cultures led to the complete depletion of CD8(+) T cells compared with enhanced activation of CD4(+) cells [as measured by expression of CD25 (IL-2Ralpha)]. By contrast, addition of a mutant EtxB, EtxB(G33D), which does not bind to GM1, failed to trigger CD8(+) T cell depletion. When EtxB was added to isolated non-immune CD8(+) lymphocytes rapid (12-18 h) alterations in nuclear morphology and the appearance of sub-G0/G1 levels of DNA were induced; properties which are characteristic of cells undergoing apoptosis. EtxB(G33D) failed to trigger apoptosis, indicating that the induction of the apoptotic signal was dependent on the binding of GM1. These findings provide an insight into the potent immunogenicity and immunomodulatory properties of E. coli enterotoxins as well as heralding a novel method for the selective induction of apoptosis in mature CD8(+) T lymphocytes.

Animals↗
PubMed1996

Reactivation of herpes simplex virus type 1 in the mouse trigeminal ganglion: an in vivo study of virus antigen and immune cell infiltration.

The corneas of latently infected mice were UV irradiated to induce reactivation of herpes simplex virus type 1 (HSV-1) in the trigeminal ganglion (TG). On days 1 to 4 after irradiation, TG were removed, serially sectioned and double stained to identify immune cells and virus antigens. Virus antigen was detected in small numbers (most commonly one) of neurons per ganglion as early as day 1, confirming the rapidity of reactivation and the neuron as the likely site of this event. The immune response was also rapid and effective since virus antigen was identified in immune cells at day 1 and by day 4 all samples were negative. The predominant infiltrating cells on days 1 and 2, when virus antigen was present and being cleared, were T cells, both CD4+ and CD8+. Later, large numbers of B cells appeared, suggesting that local antibody production may also be involved in controlling the reactivated infection. The observations suggest that a significant proportion of reactivation events do not result in disease of the eye or shedding of virus in the tear film. However, they also suggest that as little as one reactivating neuron in the ganglion may be sufficient to lead to such disease and/or shedding.

Animals↗
PubMed1995

Presentation of soluble and bacterial antigens by milk-derived cells to unprimed bovine T cells in vitro.

The ability of cells isolated from bovine milk and peripheral blood to present soluble protein and particulate bacterial antigens to peripheral blood T lymphocytes was compared using a culture system which consistently supports antigen-specific, primary, proliferative responses. The present study shows that cells from blood and from milk can present antigen to unprimed T cells. Major histocompatibility complex class II restriction of the responses was demonstrated by abrogation of proliferation by the addition of anti-bovine class II monoclonal antibody to cultures. Although cells derived from blood or milk were shown to be capable of presenting antigen to T cells, differences in optimal culture conditions and kinetics of the resulting response were observed.

Animals↗
PubMed1995

Immunologically ignorant autoreactive T cells, epitope spreading and repertoire limitation.

The factors that may cause antigen-presenting cells to alter the pattern of protein processing and presentation to autoreactive T cells, and thereby stimulate autoimmune disease, are currently under debate. In this article, Chris Elson and colleagues suggest that cytokines associated with T helper 1 (Th1) cells alter the processing of proteins and that this effect can be counteracted by Th2-associated cytokines.

Animals↗
PubMed1995

Immunohistochemical detection of T-cell subsets and other leukocytes in paraffin-embedded rat and mouse tissues with monoclonal antibodies.

We describe a method for immunohistochemical localization of T-cells, CD4+ T-cells, CD8+ T-cells, B-cells, activated lymphocytes, major histocompatibility complex (MHC) class II antigens, macrophages, dendritic cells, and granulocytes in rat and mouse tissue fixed in periodate-lysine-paraformaldehyde (PLP) and embedded in paraffin. Rat and mouse spleen and eyes were fixed in PLP for 18-24 hr, rapidly dehydrated, infiltrated under vacuum with paraffin at 54 degrees C, sectioned, and stained with appropriate monoclonal antibodies (MAbs). Sections of PLP-fixed, paraffin-embedded spleen were compared with acetone-fixed frozen spleen sections with respect to morphology and staining quality. Nine of 10 MAbs to rat antigens and eight of nine MAbs to mouse antigens stained paraffin sections equally or more intensely than frozen sections. The two MAbs that showed weaker staining still gave good staining on paraffin sections. Paraffin-embedded rat and mouse eyes were easier to section serially than frozen eyes, showed superior morphology, and individually stained cells were readily identified. Therefore, a combination of PLP fixation and low-temperature paraffin embedding permits detection of the major types of immune cell in rat and mouse tissues while maintaining good morphology, particularly in diseased, damaged, or delicate tissues.

Animals↗
PubMed1994

Psychological reactance: effects of age and gender.

A self-report, attitudinal questionnaire was administered to 1,717 adult Australians between 18 and 40 years old to examine the effects of age and gender on psychological reactance. Analysis yielded a significant age effect: As age increased, the level of reactance tended to decrease. No significant differences in reactance emerged in relation to gender. A significant interaction between age and gender was found.

Adolescent↗
PubMed1994

Gene duplications and the origins of vertebrate development.

All vertebrates possess anatomical features not seen in their closest living relatives, the protochordates (tunicates and amphioxus). Some of these features depend on developmental processes or cellular behaviours that are again unique to vertebrates. We are interested in the genetic changes that may have permitted the origin of these innovations. Gene duplication, followed by functional divergence of new genes, may be one class of mutation that permits major evolutionary change. Here we examine the hypothesis that gene duplication events occurred close to the origin and early radiation of the vertebrates. Genome size comparisons are compatible with the occurrence of duplications close to vertebrate origins; more precise insight comes from cloning and phylogenetic analysis of gene families from amphioxus, tunicates and vertebrates. Comparisons of Hox gene clusters, other homeobox gene families, Wnt genes and insulin-related genes all indicate that there was a major phase of gene duplication close to vertebrate origins, after divergence from the amphioxus lineage; we suggest there was probably a second phase of duplication close to jawed vertebrate origins. From amphioxus and vertebrate homeobox gene expression patterns, we suggest that there are multiple routes by which new genes arising from gene duplication acquire new functions and permit the evolution of developmental innovations.

Amino Acid Sequence↗
PubMed1992

PROBIT: weighted probit regression analysis for estimation of biological activity.

PROBIT estimates biologic activity by weighted probit regression analysis and comparison with a known standard. The program is intended to speed up calculation of the concentration of cytokines in large numbers of cell supernatants. Data are input from either sequential or free-form text files created with a spreadsheet or text editor. This allows transfer of data from a beta-counter equipped with a suitable terminal without retyping. Results are displayed and/or printed as relative potency (% of standard) and 50% effective dose (ED50).

Cytokines↗
PubMed1992

Depressed potential for interleukin-2 production following early weaning of piglets.

Spleen cells, but not mesenteric lymph node cells, from 3-week-old piglets abruptly weaned onto a soya-based diet, produced less interleukin-2 (IL-2) following non-specific activation with concanavalin A (Con A) than did cells from age- and litter-matched, unweaned controls. In contrast, the ability to express receptors for IL-2 was only marginally reduced. The effect on IL-2 production was most marked in animals weaned for as little as 24-48 h. Variation within groups increased with time after weaning, indicating differences between individuals in the longer-term effects of weaning. This finding may be due to endogenous production of steroids resulting in generalised impaired immune function or to retention of cells within intestinal sites owing to an active local immune response.

Animals↗
PubMed1992

Impaired T-cell priming and proliferation in cats infected with feline immunodeficiency virus.

OBJECTIVE: Cats naturally infected with feline immunodeficiency virus (FIV) are particularly susceptible to infection with opportunistic pathogens, suggesting that these animals are unable to develop an effective immune response against the pathogen. Previous studies have used CD4+:CD8+ lymphocyte ratios and mitogen blastogenesis to identify immunological abnormalities in FIV-infected cats. However, these studies provide limited information for understanding the nature of the cellular dysfunction in FIV-infected cats, particularly defects in antigen-specific immune responses. DESIGN: To investigate whether cats infected with FIV are less able to mount an immune response to previously unencountered antigens, we compared the development of antigen-specific cellular immunity at the stage of T-cell priming in uninfected and FIV-infected cats. INTERVENTIONS: The general immune status of cats was assessed by peripheral blood CD4+:CD8+ lymphocyte ratios (flow cytometry), and by lymphocyte blastogenesis response to T- and B-cell mitogens. In addition, we describe the development of an autologous culture system to measure specific priming of naive feline T-cells to soluble antigen in vitro. This assay was used to compare T-cell priming in uninfected cats and cats which had been infected with FIV for 6-27 months. RESULTS: As in HIV infection, CD4+:CD8+ lymphocyte ratios in FIV-infected cats were found to be inverted, due to a reduction in the percentage of CD4+ cells. In addition, lymphocyte blastogenesis to both T- and B-cell mitogens was significantly impaired in FIV-infected cats. Priming to keyhole limpet haemocyanin (KLH) elicited a late proliferative response resulting from the expansion of CD4+ (T-helper cells). T-cell growth factor secretion correlated with cell proliferation. Restimulation of cells with fresh antigen-presenting cells and antigen showed that antigen-specific T-cell priming had occurred in the initial culture. When primary proliferation responses in FIV-infected cats were examined, it was observed that naive CD4+ T-cells from FIV-infected cats were significantly impaired (P less than 0.001) in their ability to be primed to KLH when compared with uninfected controls. CONCLUSIONS: Impaired priming of naive CD4+ T-helper cells to antigen in FIV-infected cats may explain the increased susceptibility of these animals to infection by opportunistic pathogens. The poor ability of human patients with AIDS to develop humoral immunity following vaccination may also be caused by such a defect in T-cell priming.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Red cell autoantibody production by colonic mononuclear cells from a patient with ulcerative colitis and autoimmune haemolytic anaemia.

We have studied the ability of mononuclear cells extracted from the colon (CMC), draining lymph nodes (LNMC), peripheral blood (PBMC) and spleen (SMC) of a patient with ulcerative colitis and severe autoimmune haemolytic anemia to produce red cell autoantibodies. The LNMC, PBMC and SMC secreted immunoglobulin in vitro in pokeweed mitogen culture but not spontaneously. They also produced immunoglobulin when transferred to severe combined immunodeficient (SCID) mice but no anti-red cell activity was demonstrable. In contrast, in vitro cultures of CMC produced immunoglobulin spontaneously, showing the presence of activated B-cells and plasma cells, but anti-red cell activity could not be demonstrated. However, CMC transferred to SCID mice were able to produce IgG with anti-red cell activity. These results concur with clinical observations suggesting that the colon is the source of red cell autoantibodies in these patients.

Adult↗
PubMed1992

An early defect in primary and secondary T cell responses in asymptomatic cats during acute feline immunodeficiency virus (FIV) infection.

As in HIV infection of humans, cats infected with FIV are particularly susceptible to secondary infection by opportunistic pathogens, suggesting an impaired ability to elicit an effective immune response against foreign antigens. In order to investigate the development of immunity in FIV-infected cats, we have used an autologous culture system to directly measure priming of naive CD4+ T cells to soluble protein antigen, in vitro. Using this assay, we showed previously that cats infected with FIV for several months had significantly reduced primary proliferative responses. We have now examined cats before infection, and at varying times after infection with FIV, to determine how soon after infection this defect in T cell priming was evident, compared with other quantitative and qualitative measurements of lymphocyte function. Our results showed a progressive decline in immune function in asymptomatic cats during the acute stage of infection with FIV. Primary T cell responses were most sensitive and a significant reduction in proliferation of naive T cells to foreign antigen occurred 5 weeks after infection, despite normal blastogenesis to T cell mitogens and normal CD4+/CD8+ ratios at these times. Whilst lymphocyte proliferation to T cell mitogens was unaffected throughout, a significant reduction in proliferation to a B cell mitogen occurred from week 8 onwards. CD4+/CD8+ ratios fell significantly from week 13 onwards, and proliferation of the memory T cell population to a recall antigen was significantly impaired later, from week 19 onwards. The defect in the priming of naive T cells to foreign antigen early after infection may be important in determining susceptibility to secondary infections.

Animals↗
PubMed1992

An amphioxus homeobox gene: sequence conservation, spatial expression during development and insights into vertebrate evolution.

The embryology of amphioxus has much in common with vertebrate embryology, reflecting a close phylogenetic relationship between the two groups. Amphioxus embryology is simpler in several key respects, however, including a lack of pronounced craniofacial morphogenesis. To gain an insight into the molecular changes that accompanied the evolution of vertebrate embryology, and into the relationship between the amphioxus and vertebrate body plans, we have undertaken the first molecular level investigation of amphioxus embryonic development. We report the cloning, complete DNA sequence determination, sequence analysis and expression analysis of an amphioxus homeobox gene, AmphiHox3, evolutionarily homologous to the third-most 3' paralogous group of mammalian Hox genes. Sequence comparison to a mammalian homologue, mouse Hox-2.7 (HoxB3), reveals several stretches of amino acid conservation within the deduced protein sequences. Whole mount in situ hybridization reveals localized expression of AmphiHox3 in the posterior mesoderm (but not in the somites), and region-specific expression in the dorsal nerve cord, of amphioxus neurulae, later embryos and larvae. The anterior limit to expression in the nerve cord is at the level of the four/five somite boundary at the neurula stage, and stabilises to just anterior to the first nerve cord pigment spot to form. Comparison to the anterior expression boundary of mouse Hox-2.7 (HoxB3) and related genes suggests that the vertebrate brain is homologous to an extensive region of the amphioxus nerve cord that contains the cerebral vesicle (a region at the extreme rostral tip) and extends posterior to somite four.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1992

Primary antigen-specific T-cell proliferative responses following presentation of soluble protein antigen by cells from the murine small intestine.

To understand the local immune events which occur when a novel antigen is encountered in the gut it is necessary to know whether cells from the mucosal tissues are capable of initiating T-cell reactivity. We have examined the capacity of cells isolated from the Peyer's patches and the lamina propria of the murine small intestine to present keyhole limpet haemocyanin (KLH) to naive syngeneic splenic T cells in vitro. The properties of the gut antigen-presenting cells (APC) were compared with those of cells from the spleen and the mesenteric lymph nodes. Results clearly demonstrate that cells from the lamina propria as well as from the Peyer's patches, mesenteric lymph node and spleen can present KLH to naive T cells, inducing strong proliferative reactions comparable in magnitude and kinetics. All the APC populations tested induced interleukin-2 (IL-2) production in primary cultures, although minor differences were noted when lamina propria cells were used as APC. IL-4 was not detected in supernatants from cultures of non-immune T cells in the presence of APC from any tissue. Phenotypic analysis of the cells in cultures of naive T cells, with antigen and APC from different gut-associated tissues revealed important differences. Cells from Peyer's patch, mesenteric lymph node and spleen gave rise to cultures containing largely CD4+CD8- cells. However, cultures in which lamina propria cells acted as APC consisted primarily of CD4-CD8+ cells.

Animals↗
PubMed1991

Cloning of segment polarity gene homologues from the unsegmented brachiopod Terebratulina retusa (Linnaeus).

We have used the polymerase chain reaction (PCR) to amplify, clone and sequence homologues of the Drosophila segment polarity genes engrailed (en), cubitus interruptus Dominant (ciD) and wingless (wg) from the genome of the brachiopod, Terebratulina retusa (Linnaeus). The deduced translation products of brachiopod en and ciD share high levels of sequence identity with their Drosophila homologues. The brachiopod wg-related clone is divergent from Drosophila wg, although clearly a member of the wg/Wnt gene family. These results indicate that structural diversity of Drosophila segment polarity genes has been evolutionarily conserved in a divergent, ancient and unsegmented animal phylum.

Amino Acid Sequence↗
PubMed1991

A molecular analysis of the phylogenetic affinities of Saccoglossus cambrensis Brambell & Cole (Hemichordata).

Traditional approaches to phylogeny reconstruction have not allowed precise resolution of the evolutionary relationships between the major deuterostome phyla (chordates, hemichordates, echinoderms). Here we report the use of a molecular approach to investigate deuterostome phylogeny. We have used a polymerase chain reaction-based strategy to amplify, clone and sequence parts of the genes coding for 18S ribosomal RNA from Saccoglossus cambrensis (Hemichordata), Arbacia sp. (Echinodermata) and, for comparison, Mytilus edulis (Mollusca). We report the results of phylogenetic reconstructions using these, and homologous sequences from other eukaryotes. The results of our analyses are consistent with the hypothesis that S. cambrensis and vertebrates share a common ancestor not shared by echinoderms.

Animals↗