Biomedical subjects

J R Lamb

Publications and source records attributed to J R Lamb.

At least 73 records · Page 4Linked to original sources

PubMed1995

Clonal analysis of CD4 mediated accessory function on the effector activity of human CD4+ T cell subsets.

BACKGROUND: It has been reported for the peripheral T cell repertoire that CD4 molecules may enhance adhesion between T cells and antigen presenting cells and, through their physical association with T cell antigen receptors, contribute to signal transduction. OBJECTIVE: The aims of this study were to determine if the modulation of CD4 molecules had differential effects on T cell recognition, antigen induced cytokine (IL-4 and IFN gamma), release and the induction of specific anergy for human TH-0, Th-1 and TH-2 cells. METHODS: A panel of anti-CD4 antibodies was examined for its ability to modulate T cell proliferation, cytokine production and tolerance induction in house dust mite (TH-0 and TH-2) and influenza haemagglutinin (TH-1) specific human CD4+ T cell clones all restricted by DRB1*1101 and isolated from dust mite allergic individuals. RESULTS: We observed that anti-CD4 antibodies may inhibit or enhance antigen mediated T cell proliferation, which may reflect the differential requirements of T cells for selective functions of CD4. Furthermore, IFN gamma and IL-4 production was differentially modulated depending on the specificity of the anti-CD4 antibody and the clone of T cells. However, pretreatment of T cells with anti-CD4 antibody alone neither induced nor enhanced the susceptibility of T cells to peptide mediated anergy. CONCLUSION: Antigen recognition by different subsets of human CD4+ T cells has differential requirements on CD4, whereas the induction of specific anergy appeared to be independent of the functions of CD4 molecules. Antigen induced IFN gamma production was more susceptible than IL-4 to the inhibitory effects of anti-CD4 antibodies. Furthermore, it appeared that certain anti-CD4 antibodies can dissociate antigen induced IFN gamma and IL-4 production, and may downregulate IFN gamma synthesis without inhibiting antigen dependent proliferation.

Antibodies↗

PubMed1995

Differential dependence of TH-0, TH-1 and TH-2 CD4+ T cells on co-stimulatory activity provided by the accessory molecule LFA-1.

BACKGROUND: The adhesion molecule LFA-1 contributes to the activation response of peripheral blood human CD4+ T cells. Less is known of its contribution to stimulation of long-term CD4+ T cell lines and clones or of its potential to co-stimulate CD4+ T cells of different functional phenotype. OBJECTIVE: This study was therefore performed to investigate co-stimulatory properties of the LFA-1 (CD11a/CD18) complex in the activation of human CD4+ T cell lines and clones of TH-0, TH-1 and TH-2 subsets. METHODS: Co-stimulatory activity was measured by cross-linking antibodies to CD11a or CD18 with anti-CD3 antibodies to plastic and then measuring the proliferative response of CD4+ T cells to these antibodies. RESULTS: A house duct mite allergen-specific CD4+ T cell line (TH-2) demonstrated much greater dependence on both CD11a and CD18 than a mycobacterial antigen-specific CD4+ T cell line (TH-1). Co-stimulatory activity through LFA-1 was also provided to a house dust mite-specific CD4+ T cell clone (DE-9; TH-2) but not to an influenza haemagglutinin-specific CD4+ T cell clone (HA1-7; TH-0). In contrast, soluble antibodies to CD18 inhibited proliferative responses of both DE-9 and HA1.7 to an immunogenic challenge of antigen and to stimulation by anti-CD3 antibodies. However, the allergen-specific T cells were more susceptible to inhibition. Signal transduction was also observed from the T-cell receptor to LFA-1. Ligation of the T-cell receptor modulated the phenotypic expression of LFA-1 and ICAM-1 on both HA1.7 and DE-9. Phenotypic modulation was observed as a result of both activation and the induction of non-responsiveness. CONCLUSION: These experiments indicate that CD4+ T cells of TH-2 functional phenotype may have a greater requirement for the co-stimulatory activity of LFA-1 than CD4+ T cells of TH-0 or TH-1 phenotypes.

Antibodies, Monoclonal↗

PubMed1995

Human CD4+ T-cell repertoire of responses to influenza A virus hemagglutinin after recent natural infection.

The human CD4+ T-cell repertoire of responses to hemagglutinin (HA) of influenza virus A/Beijing/32/92 was examined 3 to 6 months after natural infection by using a panel of 16-mer peptides overlapping by 11 residues. Short-term CD4+ T-cell lines were derived by using full-length HAs of virus A/Beijing/32/92 from 12 unrelated, major histocompatibility complex (MHC) class I and II haplotyped adults with a history of influenza in November and December 1993 and from 6 adults with no history of influenza during the preceding 4 years but who responded to HA. In contrast to recent murine studies, the human CD4+ T-cell repertoire of responses was dominated by the recognition of highly conserved epitopes. The HA2 subunit, widely regarded as nonimmunogenic, induced strong responses in every donor. This resulted in functional cross-reactivity among influenza A viruses. Our study included one pair of unrelated donors expressing identical HLA DRB1 and DQB1 alleles and two pairs of donors sharing low-resolution MHC class II types. These pairs responded to identical peptides; furthermore, clearly identifiable patterns of response were seen in donors sharing single class II haplotypes, irrespective of the presence of other alleles and exposure history. Two conserved regions which induced responses in 17 of 18 donors were identified (residues 295 to 328 and 407 to 442). Possible implications for cross-reactive T-cell vaccines are discussed.

Adult↗

PubMed1995

Evidence for a superantigen mediated process in Kawasaki disease.

The clinical, pathological, and immunological similarities between Kawasaki disease and the staphylococcal and streptococcal toxic shock syndromes suggest that a superantigen toxin may be involved in the pathogenesis of the disease. The V beta repertoire of peripheral blood mononuclear cells from 21 children with Kawasaki disease, 28 children with other illnesses, and 22 healthy controls were examined using monoclonal antibodies to V beta 2, 5, 8, 12, and 19. The mean percentage of V beta 2 expressing T cells in the patients with Kawasaki disease was increased when compared with healthy controls or children with other illnesses. The mean percentages of V beta 5, 8, 12, and 19 expressing T cells were also increased in the patients with Kawasaki disease compared with healthy controls, but were not increased when compared with children with other illnesses. The selective use of V beta 2 supports the hypothesis that a superantigen is involved in the pathogenesis of Kawasaki disease.

Acute Disease↗

PubMed1995

The domain structure and functional relationships in the bacterial superantigen, SEB.

Staphylococcal enterotoxin B (SEB) has three essential biological properties that appear to be mediated by particular domains of the protein. As a superantigen, SEB triggers the T cell receptor (TcR) of a selected subset of T cells where the beta chain is encoded by particular V beta gene products. T cell triggering is generally dependent upon the ability of SEB to form a ternary complex with the TcR and MHC class II molecules and this interaction is relatively unrestricted by class II polymorphism. The third property of SEB is its potent toxicity; a few nanograms are sufficient to cause vomiting and violent diarrhoea in primates. In this study, we confirm the importance of the amino terminal domain of SEB for stimulation of human T cells. It is clear that the first 138 residues are the minimal mitogenic component of the toxin, and deletion of just seven more residues abrogates all activity. A mutant molecule with an internal deletion of these seven residues (SEB delta 131-138) was mitogenic suggesting that the region can confer stability to the rest of the protein, but does not include contact sites for either class II or the TcR. We further show that the disulphide loop is not essential for T cell recognition and that each of our mutants binds class II molecules with reduced affinity and is subtly variant in the pattern of TcR that it stimulates.

Amino Acid Sequence↗

PubMed1995

An immunogenetic analysis of the T-cell recognition of the major house dust mite allergen Der p 2: identification of high- and low-responder HLA-DQ alleles and localization of T-cell epitopes.

Cellular reactivity to Der p 2, a major allergen of the house dust mite (HDM) Dermatophagoides pteronyssinus, was studied in a group of 41 symptomatic HDM sensitive patients, using fresh peripheral blood mononuclear cells (PBMC) and assays of proliferation. Sixty per cent of the patients responded to Der p2, with reactivities being greater in patients with asthma as one of their clinical manifestations and also in those who had skin-test reactivity to a number of allergens. HLA-DR and -DQ serotyping was undertaken in 39 of the patients and the magnitude of T-cell proliferative responses to Der p 2 were found to be positively associated with DQ7 and negatively associated with DQ2. T-cell determinants within the Der p 2 molecule were identified by assays using a series of overlapping peptides (15- to 19-mers) spanning the entire protein. Fifty-nine per cent of the 41 HDM-sensitive patients responded to one or more of the peptides. All of the peptides were antigenic for at least one of the individuals, indicating the heterogeneity of the human repertoire reactive with Der p 2. There was a substantial variability in the number and location of epitopes recognized by T cells from the different allergic patients, the mean number per patient being 2.3 +/- 1.3 (SD). The most frequently recognized peptide was that spanning residues 111-129, being stimulatory in 66.7%, the other peptides were each recognized by between 8 to 25% of individuals. There was no correlation between the epitope recognized and the presence of particular HLA-DQ antigens.

Adolescent↗

PubMed1995

Polyclonal and clonal analysis of human CD4+ T-lymphocyte responses to nut extracts.

The induction of IgE antibodies to aeroallergens depends upon antigen-specific CD4+ helper T cells of an 'interleukin-4 (IL-4)-dominant' phenotype. Nuts also drive IgE-mediated hypersensitivity and are the most dangerous of the orally encountered allergens. We have studied the polyclonal T-cell responses of atopic and non-atopic individuals to extracts of peanut, brazilnut and hazelnut. Strong proliferative responses were observed in all patients but specific IgE was only present in the nut-allergic patients suggesting a similar pathogenic mechanism to aeroallergen-mediated hypersensitivity. To investigate this hypothesis a panel of peanut-reactive T-cell clones was raised from a peanut- and brazilnut-allergic individual without hazelnut allergy. The antigen specificity, major histocompatibility complex (MHC) class II restriction and cytokine profiles of the T-cell clones were determined. With the exception of one T-cell clone, which proliferated in response to both peanut and hazelnut extract, the peanut T-cell clones were not cross-reactive with hazelnut or brazilnut. The T-cell clones recognized antigen in association with HLA-DR and HLA-DP but not HLA-DQ class II molecules. The peanut-specific clones produced high levels of IL-4 and low levels of interferon-gamma (IFN-gamma), exhibiting the 'TH2-like' profile which dominates the aeroallergen response. In contrast, the T-cell clone that was cross-reactive on both peanut and hazelnut allergen had a Th0-like phenotype, consistent with the lack of specific serum IgE to hazelnut. These results support the importance of functionally distinct T-cell populations that recognize oral allergens. The relative production of IL-4 and IFN-gamma of the cloned T cells in the peanut-allergic patients plays a role in determining whether or not IgE antibody responses are induced with the associated potential to develop anaphylactic reactions.

Adult↗

PubMed1995

The effects of changes at peptide residues contacting MHC class II T-cell receptor on antigen recognition and human Th0 cell effector function.

Cytokines can influence the selection of functional subsets (Th1 or Th2) of CD4+ T cells. However, quantitative changes in affinity of peptide/major histocompatibility complex (MHC) class II/T-cell receptor (TCR) interactions may alter antigen density and modulate T-cell effector function. The possibility exists to use peptide analogues to induce a partial signal to dissociate production of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) by T-helper type-0 (Th0) cells and, consequently, to regulate T-cell function. Based on binding assays and resolution of the crystalline structure of an influenza virus haemagglutinin peptide (HA 306-318) bound to the human MHC class II molecule DRB1*0101, we synthesized HA peptide analogues with amino acid substitutions predicted to modify either MHC class II/peptide density or TCR/peptide interactions. When we examined their antigenicity using cloned human Th0 cells, the analogues, in general, elicited a gradation in potency reflected by a reduction in both proliferation and cytokine production (IL-2, IL-4 and IFN-gamma). Although the analogue HA-R309 diminished IL-2 production, none of the analogues tested could selectively induce only IL-4 or IFN-gamma. Since, in general, the effector functions of the Th0 cells examined here were resistant to selective manipulation by the peptide analogues, this suggests that for some clones of chronically activated T cells modulation of selected functions may be difficult to achieve.

Amino Acid Sequence↗

PubMed1994

Immunosuppressant deoxyspergualin inhibits antigen processing in monocytes.

Deoxyspergualin (DSG) is a novel immunosuppressive agent recently shown to bind to the constitutive heat shock protein 70, which is involved in binding and intracellular transport of antigenic peptides. In this study, we show that DSG inhibits the proliferation of PBMCs to the Ags tetanus toxoid and diphtheria toxoid, but not to the mitogens PHA and PMA/ionomycin, nor to the superantigens toxic shock syndrome toxin-1 and staphylococcal enterotoxin A. DSG's effect was specific for monocytes as preincubation of T cells with DSG did not inhibit their proliferation to monocytes pulsed with tetanus toxoid Ag for 16 h, whereas the presence of DSG during Ag pulsing of the monocytes inhibited their ability to stimulate T cell proliferation. DSG did not down-regulate the expression of MHC class II molecules by monocytes, and the inhibitory effect of DSG on T cell proliferation was not reversed by the addition of IL-2, nor by the addition of the costimulatory signals IL-1, IL-6, and anti-CD28. Studies with two human T cell clones, HA1.7 and PF5, specific, respectively, to peptides spanning amino acids 307-319 and 256-270 of influenza hemagglutinin, showed that DSG inhibited the proliferation of the clones to the native hemagglutinin molecule but minimally affected their proliferation to the peptides. These data suggest that DSG interferes with Ag processing and/or presentation.

Adult↗

PubMed1994

Cdc16p, Cdc23p and Cdc27p form a complex essential for mitosis.

Cdc16p, Cdc23p and Cdc27p are all essential proteins required for cell cycle progression through mitosis in Saccharomyces cerevisiae. All three proteins contain multiple tandemly repeated 34 amino acid tetratricopeptide repeats (TPRs). Using two independent assays, two-hybrid analysis in vivo and co-immunoprecipitation in vitro, we demonstrate that Cdc16p, Cdc23p and Cdc27p self associate and interact with one another to form a macromolecular complex. A temperature sensitive mutation in the most highly conserved TPR domain of Cdc27p results in a greatly reduced ability to interact with Cdc23p, but has no effect on interactions with wild-type Cdc27p or Cdc16p. The specificity of this effect indicates that TPRs can mediate protein-protein interactions and that this mutation may define an essential interaction for cell cycle progression in yeast. The conservation of at least two of the three proteins from yeast to man suggests that this protein complex is essential for mitosis in a wide range of eukaryotes.

Amino Acid Sequence↗

PubMed1994

Binary and ternary complexes between T-cell receptor, class II MHC and superantigen in vitro.

Superantigens are proteins that in association with class II major histocompatibility complex (MHC)-bearing cells can stimulate virtually all T cells that express particular classes of the variable beta-domains of the T-cell receptor (TCR). This mechanism of T-cell activation circumvents the usual requirement for peptide-specific MHC recognition. Staphylococcus aureus enterotoxin B (SEB) is a bacterial superantigen that causes food poisoning and shock. We have characterized the tertiary complex of SEB, a soluble T-cell receptor, and a soluble class II MHC molecule DR1, and the three binary complexes TCR-SEB, SEB-DR1, and the peptide-specific complex DR1-TCR. We report here that in each case the specificity of the interaction among the soluble molecules is the same as observed in biological assays. Native gel electrophoresis and plasmon resonance affinity measurements indicate that SEB-TCR complex can form in the absence of class II MHC and that SEB-TCR interaction increases the binding of DR1. The observation that a superantigen can form complexes with TCR in both the absence and presence of class II MHC may provide a mechanism for its ability to induce anergy in some circumstances and activation in others (reviewed in ref. 8).

Amino Acid Sequence↗

PubMed1994

Degeneracy of T cell receptor recognition of an influenza virus hemagglutinin epitope restricted by HLA-DQ and -DR class II molecules.

DT9301-0229737 the TcR are believed to provide the peptide fragments bound to major histocompatibility (MHC) molecules. TcR have an immunoglobulin (Ig)-like structure and, in an analogous manner to antigen recognition by Ig, the third complementarity determining regions (CDR3) of the TcR are believed to provide the primary contact with the peptide lying in the MHC groove. CDR1 and CDR2 are thought to contact the presenting MHC molecule. We have analyzed seven human CD4+ T cell clones that recognize a conserved peptide epitope (residues 255-270) within the influenza virus hemagglutinin (H3) HA1 subunit. Two T cell clones recognized the peptide in the context of HLA-DRB1*1001 and HLA-DQB1*0602/DQA1*0102, respectively, and shared V alpha, V beta and J beta gene segments. Only the junctional regions encoding the CDR3 regions of the two TcR chains were different. This suggests that the CDR3 regions of these TcR interact with the MHC class II molecule. Six of the T cell clones were restricted by the HLA-DRB1*1001. Two of these T cell clones expressed V beta 9.1 and three expressed V beta 13 gene segments; the remaining clone expressed V beta 7.2, a close homologue of V beta 9.1. A diverse selection of V alpha and J gene segments contributed to the junctional heterogeneity of the TcR, indicating a diversity of sequence combinations recognizing the epitope. Nevertheless, five out of six T cell clones bore a motif in the V alpha CDR3 loop consisting of adjacent acidic and polar amino acid residues, eight residues from the carboxyl end of each CDR3.

Amino Acid Sequence↗

PubMed1994

CD4+ T cell-targeted immunomodulation and the therapy of allergic disease.

In recent years there have been considerable advances in our knowledge of the cellular and molecular events following ligation of the T cell receptor. The quantitative and qualitative characteristics of the signal(s) received by a naive or memory T cell largely determine whether receptor ligation results in cell activation, cell death, or the induction of a state of antigen-specific nonresponsiveness. Furthermore, microenvironmental conditions, including the presence of secreted cytokines or the structure of the peptide antigen, strongly influence the differentiation of CD4+ helper cells into functionally distinct subsets. The interregulation of these functional subsets appears pivotal to the development of many immune-mediated disorders, including allergic disease. We suggest that the selective manipulation of the immune response to specific antigens may be an effective strategy for the therapy of such disorders and we review recent studies which support this concept.

Adjuvants, Immunologic↗

PubMed1994

Inhibition of human T-cell responses to house dust mite allergens by a T-cell receptor peptide.

Recent analysis of the usage of T-cell receptor (TcR) beta chain variable region (V beta) gene elements by house dust mite (HDM)-reactive T cells from an atopic donor suggested that TcR-V beta 3 gene products may form a major component of the human T-cell repertoire reactive to this common allergen. In this study a peptide analog of the TcR-V beta 3 complementarity determining region 2 (CDR2) is shown to inhibit the polyclonal human T-cell response to HDM; this effect is specific because inhibition is dependent on the presence of V beta 3 + T cells. This experimental approach has been used to determine whether the pattern seen in T-cell clones derived from one atopic donor reflects TcR-V beta usage in the polyclonal response to allergen in the general population. Inhibition of more than 50% of the polyclonal response to allergen by V beta 3-CDR2 peptide was observed in 16 of 21 donors tested, suggesting that TcR-V beta 3 gene usage may form a major component of the human HDM repertoire and as such offer a suitable target for T cell-directed specific immunotherapy in HDM-allergic individuals. Depletion of CD8+ T cells abolishes peptide-mediated inhibition of CD4+ T-cell proliferation to HDM, suggesting that induction of a CD8+ regulatory T-cell subset by the CDR2 peptide may modulate HDM-specific allergic T-cell responses.

Allergens↗

PubMed1994

Overlapping T-cell epitopes in the group I allergen of Dermatophagoides species restricted by HLA-DP and HLA-DR class II molecules.

The induction of IgE antibodies reactive with the group I allergen of Dermatophagoides species (house dust mite [HDM]), which comprise a major component of the allergic immune response in HDM-atopic individuals, is dependent on the functional activity of specific CD4+ T cells. In this report we demonstrate that for a particular HDM-atopic individual the T-cell response to the group I allergen of Dermatophagoides pteronyssinus (Der p I) is limited to a single region (residues 101-143) of the protein. By mapping the fine antigen specificity with T-cell clones, we observed that the sequence 101-131 of Der p I contains a cluster of at least three overlapping T-cell epitopes. Analysis of the HLA class II restriction specificity of the T-cell clones revealed that the T-cell epitope, residues 110-131, was restricted by HLA-DRB1*0101. In contrast, peptide Der p I, 110-119 was recognized in association with HLA-DPB1*0402. However, the ability of cloned T cells to proliferate to the peptide Der p I, 107-119 presented by HLA-DPB1*0401, HLA-DPB1*0402, and HLA-DPB1*0501 expressing accessory cells illustrates the heterogeneity of the restriction specificity of this region of Der p I. The application of this information in the design of peptide-based immunotherapy in the management of allergic responses to HDM is discussed.

Allergens↗

PubMed1994

Identification of two binding sites in staphylococcal enterotoxin B that confer specificity for TCR V beta gene products.

The enterotoxins produced by Staphylococcus aureus are potent mitogens. They stimulate T cells in an oligoclonal fashion that is dependent on the expression of particular variable region gene elements in the beta-chain of the TCR (V beta). The fourth hypervariable loop of the TCR beta-chain is generally regarded as the site of contact for both viral and microbial superantigens. Recently, residues 60 and 61 of staphylococcal enterotoxin B (SEB) have been highlighted as central to the interaction of this toxin with the TCR. We have, therefore, analysed a series of toxins with mutations at these positions to investigate how amino acid substitutions affect the ability of mutant toxins to stimulate both human and mouse T cells. Each of the variant toxins induced proliferation in a murine V beta 8.3 T cell clone, whereas a V beta 8.1 T cell clone only responded to native toxin. A panel of nine human T cell clones expressing six different V beta elements, all of which responded to native SEB, was tested for reactivity to the variant toxins. Only one V beta 19.1+ T cell clone was found to be sensitive to substitution at positions 60 and 61 in a manner analogous to the murine V beta 8.1 T cell clone. Semi-quantitative analysis of the TCR V beta expression of human T cell lines expanded with native and mutant SEB revealed that none of the variant toxins could stimulate T cells that expressed V beta 19.1. Taken together, these results suggest that the interaction of mouse V beta 8.1 and human V beta 19.1 TCRs with SEB differs from other TCRs. Sequence comparisons of the different TCR V beta chains indicated that residues in the second complementarity determining region (CDR2) interact with the 60-61 loop of SEB. Therefore, a minimum of two distinct binding modules confer specificity to the interaction of the TCR with SEB.

Amino Acid Sequence↗

PubMed1994

Immunological events underlying the induction of T cell non-responsiveness.

T lymphocytes recognise antigen in the form of short peptides complexed with the class I and II products of the Major Histocompatibility Complex (MHC). Cellular activation follows T cell recognition of peptide-MHC complexes at immunogenic cell surface concentrations together with the participation of the appropriate costimulatory signals. Interaction of TCRs and peptide-MHC complexes under inappropriate conditions may result in antigen-specific non-responsiveness, commonly referred to as anergy. Here we review some recent model systems which have been employed to study the phenomenon of anergy and the use of peptides to induce antigen-specific non-responsiveness both in vitro and in vivo.

Allergens↗

PubMed1993

Inhibition of T cell and antibody responses to house dust mite allergen by inhalation of the dominant T cell epitope in naive and sensitized mice.

Antigen-specific CD4+ T cells play an important role in the allergic immune response to house dust mite (HDM) allergens in humans. The group 1 allergen of Dermatophagoides spp. is a major target antigen in both B and T cell recognition of HDM. In vitro studies have shown that the presentation of peptides to human T cells under appropriate conditions may lead to a state of specific nonresponsiveness. Therefore, to determine if peptides are able to modulate the function of allergen-reactive T cells in vivo, we have used a murine model of T cell recognition of the HDM allergen Der p 1. The results demonstrate that inhalation of low concentrations of peptide containing the major T cell epitope of Der p 1 (residues 111-139), induces tolerance in naive C57BL/6J mice such that they become profoundly unresponsive to an immunogenic challenge with the intact allergen. When restimulated in vitro with antigen, lymph node T cells isolated from tolerant mice secrete very low levels of interleukin 2, proliferative poorly, and are unable to provide cognate help to stimulate specific antibody production. Furthermore, intranasal peptide therapy was able to inhibit an ongoing immune response to the allergen in mice and this has potential implications in the development of allergen-based immunotherapy.

Administration, Inhalation↗