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M Londei

Publications and source records attributed to M Londei.

At least 73 records · Page 4Linked to original sources
PubMed1993

Inhibition of activation-induced changes in the structure of the T cell interleukin-7 receptor by cyclosporin A and FK506.

We have recently shown that activation of T cells causes structural changes in the interleukin-7 receptor (IL-7R) (Foxwell et al. Int. Immunol. 1992, 4: 277). Unactivated cells expressed a receptor characterized as a cross-linked protein of 107-kDa whereas activated cells had reduced levels of this 107-kDa complex and now express a major cross-linked product of 93 kDa. These changes in receptor expression were concomitant with the acquisition of IL-7 growth responsiveness by activated T cells. In this study, the effect of the potent immunosuppressive agents cyclosporin A and FK506 on the activation-induced responsiveness to IL-7-driven proliferation and the concomitant changes in receptor structure have been investigated. Cyclosporin A and FK506 suppressed the expression of the 93-kDa complex and the loss of the 107-kDa complex on activated cells. The presence of exogenous IL-7 inhibited the effects of the drugs on IL-7R structure, allowing expression of the 93-kDa complex. Expression of the 93-kDa complex could also be induced either by ionomycin or phorbol esters. As observed for other T cell activation parameters, only those which induced a calcium signal (ionomycin) but not protein kinase C (phorbol esters) were sensitive to the drugs. In all studies, the expression of the 93-kDa complex correlated with the ability of cells to proliferate to IL-7, and thus these results further support the hypothesis that the 93-kDa form of the IL-7R is required to transmit the cytokine's growth signal. Moreover, these data suggest that activation-induced transcriptional events are required for the expression of the 93-kDa complex and the down-regulation of the 107-kDa complex. As reported for IL-2R and IL-4R, our data also show that the expression of another T cell growth factor receptor is sensitive to the effects of cyclosporin A and FK506. These observations also have important implications for reported cyclosporin A effects on the thymus where IL-7 can act as a growth factor for thymocytes.

Cells, Cultured↗
PubMed1993

Definition of unique traits of human CD4-CD8- alpha beta T cells.

We have studied the nature of human CD4-CD8- (double negative) alpha beta T cells to determine whether they possess unique characteristics which could further differentiate them from conventional CD4+ or CD8+ (single positive) T cells. We observed that double negative TCR alpha beta+ T cells differ from single positive T cells in the following respects: (i) their T cell receptor (TCR) repertoire is different, as revealed by the analysis of 47 clones derived from three individuals and by analysis of peripheral blood lymphocytes (PBL) prior to in vitro manipulation; (ii) their in vivo CD3:TCR expression is lower before in vitro manipulation and expansion; (iii) their direct proliferative response to IL-3, which is not mediated by secondary release of other T cell growth factors. These characteristics have also been recently ascribed to murine double negative alpha beta T cells, which develop extrathymically and are considered to be a distinct T cell lineage. Our data suggest that, like their murine counterparts, human double negative alpha beta T cells may represent a distinct T cell lineage which might develop extrathymically.

CD3 Complex↗
PubMed1993

Expression of the identical V beta gene in human T-cell clones does not confer the same pattern of responsiveness to bacterial enterotoxins.

Superantigens are the most potent T-cell mitogens so far described, and are believed to activate virtually all the T lymphocytes bearing the appropriate V beta segment in their T-cell receptor (TcR). In order to determine whether the expression of the identical V beta gene confers the same pattern of responsiveness to bacterial superantigens, we have established a panel of 20 untransformed human T-cell clones expressing the V beta 6.7a gene in their TcR. The V beta usage was defined by immunostaining, using the V beta 6.7a-specific monoclonal antibody (mAb) OT145, and confirmed by DNA sequencing of the beta-chain. Although all the clones analysed expressed the same V beta gene, they had disparate patterns of proliferation to challenge with a panel of bacterial enterotoxins. This study demonstrates that the mere expression of the same V beta region by T lymphocytes does not grant an indistinguishable responsiveness to bacterial superantigens. Thus other, as yet undefined, T-lymphocyte components play a key role in the process of T-cell activation induced by bacterial superantigens, influencing the effects mediated by exogenous superantigens on human T cells.

Amino Acid Sequence↗
PubMed1992

T cell activation and antigen presentation in human thyroid autoimmunity.

In 1983, a hypothesis concerning the relevance of class II expression and antigen presentation to the induction and maintenance of endocrine autoimmunity was published. This article reviews the evidence that has been marshalled to support this concept, both in man, chiefly in Graves' disease, and in murine systems. New data concerning the multiplicity of thyroid autoantigens recognized by in vivo activated thyroid infiltrating T cells are compatible with this concept since the thyroid epithelial cells are the source of these antigens. Whether other autoimmune diseases also employ the same mechanism remains to be ascertained, as does the initial trigger for the autoimmune process.

Animals↗
PubMed1992

Activation induced changes in expression and structure of the IL-7 receptor on human T cells.

Activation of human peripheral blood T cells renders them capable of proliferating to IL-2, -4, and -7, and upregulates the receptors for IL-2 and -4. In this study the effect of activation on the receptor for IL-7 has been investigated. Scatchard analysis showed dual affinity binding of IL-7 to peripheral blood mononuclear cells (PBMC). Furthermore, activation of PBMC with anti-CD3 antibodies resulted in a 4-fold downregulation of both the high and low affinity IL-7 receptors. SDS-PAGE analysis of [125I]IL-7 cross-linked resting PBMC revealed a major complex of 104/107 kDa (reduced/non-reduced) and a minor complex of 184/178 kDa (reduced/non-reduced). In contrast, cross-linking of activated PBMC revealed a third prominent complex of 93 kDa (non-reduced) not seen on unstimulated cells. This 93 kDa complex was observed on purified activated peripheral blood T cells and T cell blasts. Moreover, on a panel of IL-7 responsive T cell clones the 93 kDa complex was the only major cross-linked product observed. These results demonstrate that T cell activation causes changes in both the level of expression of the IL-7 receptor and the nature of the proteins associated with the receptor. It is postulated that these changes in receptor structure may be related to the acquisition of responsiveness to the IL-7 growth signal.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1992

Detection of Helicobacter pylori-like organisms in the stomach of some food-source animals using a monoclonal antibody.

To investigate a possible animal reservoir of Helicobacter pylori, 15 pigs, 15 rabbits and 5 cows slaughtered for consumption were studied. Raised serum IgG levels were found in 93% of the pigs and 87% of the rabbits, but levels were normal in the cattle. In the controlled testings three of 22 humans had elevated IgG to H pylori and in all three H pylori was detected by the use of monoclonal antibody. Helicobacter pylori were identified in gastric brushings by a monoclonal antibody in 8 out of 10 pigs and 7 out of 10 rabbits. This study suggests an animal reservoir of Helicobacter pylori which may be of importance in human infection.

Animals↗
PubMed1991

Human CD4- CD8- alpha beta+ T cells express a functional T cell receptor and can be activated by superantigens.

The CD4 and CD8 molecules play an important role in the stimulation of T cells and in the process of thymic education. Most mature T cells express the alpha beta TCR and either CD4 or CD8; however, there is a small population of alpha beta+ TCR T cells that lack both CD4 and CD8. Little is known of the biology of the CD4- CD8- (double-negative) alpha beta+ TCR T cells or the nature of the Ag to which they may respond. These cells not only represent a novel population of T cells but also provide useful biologic tools to study the roles that CD4 and CD8 play in T cell activation. In this study we have addressed two questions. Firstly, whether CD4- CD8- alpha beta+ TCR T cells have functionally active TCR and, secondly, whether CD4 or CD8 is required for the activation of T cells by bacterial enterotoxins. Six double-negative alpha beta+ TCR T cell clones, propagated from two healthy donors, were challenged with a panel of nine bacterial enterotoxins. The V alpha and V beta usage of their TCR was determined by polymerase chain reaction. All of the CD4-CD8- clones proliferated in response to at least one of the enterotoxins, in a V beta-specific manner. The proliferative response of the CD4-CD8- alpha beta+ TCR T cell clones was similar in magnitude to that exhibited by CD4+ T cell clones of known V beta expression. These data clearly show that the CD4 and CD8 molecules are not required for the activation of untransformed human T cells by bacterial enterotoxins. Furthermore, these results indicate that CD4-CD8- alpha beta+ TCR T cells, normally present in all individuals, are not functionally silent, because they can be stimulated via their TCR. Their physiologic role, like that of gamma delta T cells, remains to be elucidated.

Antigens, Bacterial↗
PubMed1991

Autoantigen recognition by thyroid-infiltrating T cells in Graves disease.

Graves disease is a common form of human autoimmune thyroiditis. It shares many pathological features and HLA associations with other, less easily studied, organ-specific autoimmune conditions such as insulin-dependent diabetes mellitus, and hence it is also a useful model for understanding these other diseases. We have previously shown that thyroid-infiltrating T cells in Graves disease that have been recently activated in vivo specifically recognize autologous thyroid epithelial cells. However, the autoantigens involved were not defined. In this study, we have made use of antigen-independent T-cell cloning techniques to show that at least three different thyroid antigens, three different epitopes on a single antigen, and two HLA class II elements are involved in this recognition process in a single individual. This demonstrates that T cells that are present and activated at the site of a human autoimmune disease may show considerable heterogeneity in their recognition of autoantigen on the target tissue. This contrasts with the limited heterogeneity recently reported in some animal models and has potentially important implications for both our understanding of the autoimmune process in humans and the design of immunotherapies to reverse it.

Adult↗
PubMed1991

Preferential expression of V beta 6.7 domain on human peripheral CD4+ T cells. Implication for positive selection of T cells in man.

The peripheral T cell receptor repertoire is mainly controlled by the processes of positive and negative selection occurring in the thymus. Studies in normal or transgenic mice have provided compelling evidence for both negative and positive selection. Negative selection is characterized by partial or total disappearance from the periphery of T cells expressing certain C beta regions, which are normally present in the thymus. Positive selection is chiefly characterized, in the periphery, by an imbalanced ratio between CD4+ and CD8+ T cells expressing a given V domain. To date little information concerning positive and negative selection has been available in man. We studied the distribution of 4 V beta domains on CD4+ and CD8+ peripheral T cells of 34 healthy individuals with a wide age-range (0-96 years). One of the V beta domain studied, V beta 6.7, is preferentially expressed on CD4+ compared to CD8+ T cells (p greater than 0.001). No significant differences were observed using the other V beta domain-specific monoclonal antibodies (V beta 5.2-5.3, 8 or 12). These results provide evidence that a process of thymic education, similar to that described in murine animal models, may also take place in man.

Adult↗
PubMed1991

Cytokine assays: role in evaluation of the pathogenesis of autoimmunity.

Cytokines are protein mediators involved in inflammation, the immune response, cell growth, repair and fibrosis. All of these processes are ongoing in active autoimmune diseases such as rheumatoid arthritis (RA), and so it would be expected that many cytokines would be actively produced in RA joints or Graves' disease (GD) thyroid glands. The cDNA cloning of cytokines has permitted the generation of pure recombinant molecules, and of newer more sensitive assays, and spurred the rapid development of knowledge in this field. Here we review the molecular strategies devised to study the possible role of cytokines in the pathogenesis of RA and GD, and describe some of the initial results. After 'cataloguing' the relative abundance of various cytokines, we sought to discover which cytokines are of major importance in pathogenesis. For that purpose we used neutralizing anti-cytokine antibodies and found that TNF alpha is one of the major signals regulating the production of IL-1 in the RA but not in the osteoarthritic (OA) joint. In order to further understand the dynamics of the cytokine network, the localization of the cytokine-producing cells by immunostaining and in situ hybridization has also been performed. The latter techniques are particularly valuable for attempting to establish the role of the target cell, such as thyroid epithelium, in the pathogenesis of disease. Cytokines act on cells via binding to high-affinity receptors. The last two years has been the cDNA cloning of many molecules encoding cytokine receptor chains, and it is now possible to begin to evaluate the other half of the cytokine pathway. Taken together, there are now exciting opportunities for the molecular dissection of the cytokine events occurring in auto-immune tissues.

Animals↗
PubMed1990

Interleukin 7 is a growth factor for mature human T cells.

We have studied the capacity of interleukin (IL) 7 to support the growth and expansion of human T cell clones of different phenotype and function. All the clones studied (CD4+CD8+, CD4-CD8- Tcell receptor alpha/beta or gamma/delta) responded to IL 7. The proliferative response of all the T cell clones induced by IL 7 was routinely less than to IL2, but comparable to the IL4 response. IL 7 also induced the proliferation of resting, freshly prepared peripheral blood mononuclear cells (PBMC) or Tcell-enriched (E+) cells. The pattern of proliferation observed in the presence of IL 7 was similar, but lower in magnitude, to that induced by IL 2. In both these cells populations the response to lymphokines alone was always less than the response to lymphokines plus insolubilized anti-CD3 monoclonal antibody. In contrast IL4 produced a different pattern of responsiveness, as significant proliferation was observed only on PBMC costimulated with anti-CD3. The possibility that IL 7 mediates its growth stimulation by the IL2 pathway was excluded by the incapacity of anti-IL2 or anti-Tac monoclonal antibody, in concentrations which blocked IL2-dependent proliferation, to inhibit IL 7-dependent growth. We conclude that IL 7 is a major growth factor for human mature T cells, and its activity is not limited to lymphocyte progenitors.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1990

CD4+ T-cell clones from autoimmune thyroid tissue cannot be classified according to their lymphokine production.

In order to define whether CD4+ T cells from autoimmune and non-autoimmune thyroid tissue could be classified according to their mediator production, lymphokine production was studied in 63 thyroid-derived CD4+ T-cell clones from four patients with Graves' disease, one with Hashimoto's thyroiditis, and one with non-toxic goitre (9-12 clones per patient). The production of interleukin 2 (IL-2), gamma interferon (IFN-gamma), tumour necrosis factor alpha (TNF-alpha), lymphotoxin (LT), interleukin 6 (IL-6) and transforming growth factor beta (TGF-beta) was assessed at the mRNA level by slot-blot analysis in unstimulated clones as well as after activation with monoclonal anti-CD3 (OKT3) and IL-2. No lymphokine production was found in unstimulated clones, whereas 56% of the clones produced all six lymphokines simultaneously after stimulation. In the remaining 44% usually not more than one lymphokine was missing from the complete panel. Lymphokine mRNA concentrations varied between different clones and different patients, but, in this small sample, not between the diseases from which the clones were originated. There was a significant correlation between IL-6, LT, and IL-2 mRNA levels and T-cell helper function, which was estimated by the stimulation of thyroid microsomal autoantibody production using autologous peripheral B cells. TGF-beta and IFN-gamma mRNA expression was unrelated to T-cell help. The results demonstrate that intrathyroid T cells from autoimmune and non-autoimmune thyroid disorders cannot be classified according to their lymphokine production, unlike some results with in vitro-induced mouse T-cell clones, where two populations, Th1 and Th2, have been described. Single T cells are capable of producing a whole panel of lymphokines and thus are capable of triggering a multitude of different processes.

CD4-Positive T-Lymphocytes↗
PubMed1989

Analysis of T-cell receptor usage in activated T-cell clones from Hashimoto's thyroiditis and Graves' disease.

Rearrangements to the T-cell receptor (TcR) beta and gamma gene loci were studied in T cells derived from the thyroid glands of a patient with Hashimoto's (HT) and another with Graves' (GD) autoimmune thyroiditis. The cells studied were freshly isolated mononuclear cells, T-cell lines grown in the presence of anti-CD3 and IL-2 and T-cell clones. Numerous different rearrangements to the constant regions of TcR beta and TcR gamma and in the variable gene region of TcR beta were observed. These findings indicate that the T-cell response in autoimmune thyroiditis is multiclonal and may have implications for the epitopes recognized by autoreactive T cells and for the mechanisms of the disease.

Adult↗
PubMed1989

Intrathyroidal cytokine production in thyroid disease.

The intrathyroidal production of Interferon gamma, tumour necrosis factor alpha and beta, Interleukin-1 alpha and beta, Interleukin-6, platelet-derived growth factor A and of transforming growth factor-beta was analysed in patients with autoimmune and non-autoimmune thyroid disease. Cytokines were assessed indirectly by slot blot mRNA analysis in fresh tissue samples (unpurified cells, infiltrating mononuclear cells and thyroid follicular cells), in thyroid follicular cells in primary culture, as well as in thyroid-derived T-cell clones. The production of Interleukin-1 alpha and beta, Interleukin-6 and transforming growth factor beta was additionally measured by bioassay. Cytokine production by thyroid-infiltrating mononuclear cells generally did not differ between autoimmune and non-autoimmune samples, the whole panel of all cytokines being found in freshly purified cells as well as in thyroid-derived T-cell clones from patient with Graves' disease, as well as with multinodular non-toxic goitre. Thyroid follicular cells produced Interleukin-1 alpha, Interleukin-6 and transforming growth factor beta. Interleukin-1 and Interleukin-6 production did not differ between thyroid follicular cells from autoimmune and non-autoimmune thyroids. Transforming growth factor beta was, however, lower in non-toxic goitre than in Graves' disease and in normal thyroid tissue, but could be increased by exposure of the cells to micromolar concentrations of iodide. This seemed of special interest, as transforming growth factor beta proved to inhibit thyroid follicular cell growth in response to known growth stimuli, such as insulin-like growth factor I or epidermal growth factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoimmune Diseases↗