Search PubMed⌕ Search

Biomedical subjects

D Guy-Grand

Publications and source records attributed to D Guy-Grand.

At least 37 records · Page 2Linked to original sources
PubMed1995

Extrathymic T cell differentiation.

In the mouse, the gut mucosa is a major site of extrathymic differentiation of T cells. Recent data in this past year show that this process differs from the main thymic differentiation pathway not only in its location, but also in its use of costimulatory molecules, signal transduction modules, and mechanisms of repertoire selection. The thymus exerts an influence on the expansion of the extrathymically differentiated gut intraepithelial lymphocytes that appears to be varied in nature, including acting as a source of TCR- progenitors. All gut intraepithelial lymphocytes, whatever their extrathymic or thymic site of differentiation, have common features of activated and specialized cytotoxic cells. Other T cells may differentiate extrathymically, in particular in the liver; these later cells appear to have a very restricted, probably autoreactive repertoire, and also display natural killer cell features.

Animals↗
PubMed1994

Oligoclonal repertoire of the CD8 alpha alpha and the CD8 alpha beta TCR-alpha/beta murine intestinal intraepithelial T lymphocytes: evidence for the random emergence of T cells.

The epithelium of the small intestine in normal euthymic mice contains a large number of intraepithelial lymphocytes (IEL), some of which bear a T cell receptor alpha/beta (TCR-alpha/beta). About half of these TCR-alpha/beta IEL display the CD8 alpha alpha phenotype and the remaining have the CD8 alpha beta or the CD4 phenotypes. To examine whether TCR-alpha/beta IEL have a TCR-beta chain repertoire as diverse as that of TCR-alpha/beta lymph node lymphocytes (LNL), we used a recently described PCR technique that allows a global analysis of the TCR-beta chain repertoire. Within any given mouse, the repertoires expressed in both CD8 alpha alpha and CD8 alpha beta TCR-alpha/beta IEL populations are oligoclonal and nonoverlapping between the two subsets. The clones are largely conserved through the length of the small intestine of the same individual. However, genetically identical individuals raised under indistinguishable environmental conditions display distinct oligoclonal repertoires. Those findings indicate that few cells of CD8 alpha alpha or of the CD8 alpha beta phenotype are responsible for the repopulation of the intestinal epithelium.

Amino Acid Sequence↗
PubMed1994

Different use of T cell receptor transducing modules in two populations of gut intraepithelial lymphocytes are related to distinct pathways of T cell differentiation.

Most gut intraepithelial cells (IEL) of the mouse are T cells that bear CD8 molecules, present either as alpha-beta chain heterodimers (CD8 beta+) or as alpha chain homodimers (CD8 beta-). All CD8 beta+ IEL bear alpha/beta T cell receptors (TCR); CD8 beta- IEL bear either alpha/beta or gamma/delta TCR and are considered to be a thymus-independent (TI) population, probably arising locally from a small fraction of CD3- IEL containing the recombinant activating gene RAG proteins. Here we report that TI CD8 beta- IEL, whether bearing alpha/beta or gamma/delta TCR, contain, in normal mice, mRNAs for both zeta and Fc epsilon RI gamma chains. These chains are present in their CD3-TCR complexes as homo- or heterodimers. In contrast, only zeta chain mRNA and homodimers are found in gut CD8 alpha/beta+ IEL and in peripheral T lymphocytes. Intestinal CD3- precursor cells contain only gamma chain, and CD3- IL-2R+ thymocyte precursors only zeta chain mRNAs. Only very primitive thymocyte precursors contain detectable gamma chain mRNA, and it thus appears that Fc epsilon RI gamma chain use is switched off at a very early stage during thymocyte differentiation. Thus, T cell differentiation in the gut epithelium differs from that occurring in the thymus, from which CD8 beta+ IEL appear to derive. Use of different TCR transducing modules and CD8 accessory molecules between the TI and the thymus-derived T cell populations provides an explanation for their difference in reactivity to antigenic stimulations and thus in selection of repertoires.

Animals↗
PubMed1994

Thymic and extrathymic origins of gut intraepithelial lymphocyte populations in mice.

We have investigated the origin of intraepithelial lymphocytes (IEL) populations in the murine gut, using reconstitution experiments in which the presence of thymus-derived cells of host or donor origin is rigorously controlled: RAG-/- mutant mice which have no T cells, were injected either with the bone marrow (BM) cells of nude mice or with selected peripheral lymph node (LN) T cells of euthymic mice. In thymectomized RAG-/- mice, injection of BM cells from nude mice led, after 2 mo, to the development of a peripheral B cell compartment and to the appearance, in the gut, of IEL bearing homodimeric CD8 alpha chains and either gamma/delta or alpha/beta TCR. In RAG-/- mice with a thymus, a similar injection led to complete lymphoid reconstitution, with the additional appearance in the gut of CD4+, CD8 alpha/beta+ or CD4+CD8 alpha/alpha+ IEL, all bearing alpha/beta TCR. In contrast, injection of LN T cells into these mice reconstituted a gut IEL population made of CD4+, CD8 alpha/beta+, or CD4+ CD8 alpha/alpha+ cells, all bearing alpha/beta TCR; CD8 alpha/alpha+ TCR-gamma/delta+ or alpha/beta+ IEL were not observed. These results demonstrate that the thymus and/or thymic-derived peripheral T cells are absolutely required for the generation of CD4+, CD8 alpha/beta+, and CD4+CD8 alpha/alpha+ IEL, which are thus thymus dependent. In contrast, TCR+ CD8 alpha/alpha+ IEL appear in the absence of the thymus, and thus are thymus independent.

Animals↗
PubMed1994

Attenuation of graft-versus-host disease and graft rejection by ex vivo immunotoxin elimination of alloreactive T cells in an H-2 haplotype disparate mouse combination.

A mouse anti-interleukin-2 receptor A-chain-specific PC61-immunotoxin (PC61-IT) strongly inhibited a primary mixed lymphocyte culture and major histocompatibility complex (MHC)-restricted cytotoxicity. The allodepleted T cells retained their proliferative and cytotoxic capacities in response to third-party stimulation, showing that PC61-IT specifically deleted recipient antigen-specific T-cell clones from the donor mouse. The ability of this specific allodepletion to prevent graft-versus-host disease (GVHD) and graft rejection was investigated in vivo. IT-depleted, activated parental T lymphocytes (C3H/eB) were intravenously injected into lethally irradiated CDF1 mice. GVHD was evaluated after 6 days on the severity of gut lesions. PC61-IT-treated cells significantly reduced both donor T-cell infiltration and acceleration of epithelial renewal (a sensitive index of gut damage) as compared with those for the corresponding untreated controls. The effect of selective allo-depletion on prevention of GVHD and graft rejection was further studied after MHC-haploincompatible bone marrow (BM) transplantation. A significant increase in survival was observed in mice receiving 2 x 10(6) T-cell-depleted BM cells and 0.5 x 10(6) PC61-IT-treated T cells, because one-third were alive without GVHD (and with stable full or partial engraftment) after 100 days, whereas all the mice infused with BM and sham-treated T cells died within 80 days from GVHD, and all the mice infused with BM cells alone rejected grafts. Furthermore, specific tolerance in chimeras towards donor cells could be shown. These results as observed in an experimental in vivo model corroborate previous results obtained in vitro in humans and lead us to consider the use of this selective allodepletion in human BM transplant from donors other than identical familial siblings.

Animals↗
PubMed1993

Prenatal diagnosis of syndromes associating albinism and immune deficiencies (Chediak-Higashi syndrome and variant).

We have successfully undertaken the prenatal diagnosis of two hereditary syndromes associating albinism and immune defects. Because the genes responsible for these diseases have not yet been mapped and the immune abnormalities are too subtle to be diagnosed in utero, the prenatal diagnosis was made using a morphological approach. In the case of Chediak-Higashi syndrome, it was based on light microscopic examination of the hair shaft and on light and electron microscopic study of polymorphonuclear cells. In the syndrome associating immune deficiency and partial albinism, the Griscelli syndrome, only examination of the hair was feasible. The diagnosis was negative in 12 fetuses at risk and positive in four.

Albinism↗
PubMed1993

Gut intraepithelial T lymphocytes.

The gut mucosa, given its length, contains a very large number of T lymphocytes in the Peyer's patches and disseminated all along the mucosa. The most conspicuous element of this last compartment, the gut intraepithelial lymphocytes, represents a population of CD8+ T lymphocytes as large as that found in the largest lymphoid organ, the spleen. In spite of their numerical importance and the fact that they are in the immediate vicinity of the largest permanent antigenic stimulus in the whole organism, these cells have remained for a long time, paradoxically, the least understood of the lymphocyte populations, in their ontogeny and physiological role. It is becoming increasingly apparent that they are ontogenically more complex than the bulk of the T lymphocytes present in the lymphoid organs and are probably able to recognize a larger array of antigenic determinants than the peripheral CD8+ T lymphocytes.

Animals↗
PubMed1992

Selection of intraepithelial lymphocytes with CD8 alpha/alpha co-receptors by self-antigen in the murine gut.

We have studied T-cell receptor (TCR) and alpha/alpha CD8 expression in thymus-independent intraepithelial lymphocytes (TI IELs) from the gut of mice bearing transgenic (TG) TCR alpha beta specific for the male antigen, presented by H-2Db class I major histocompatibility complex (MHC) molecules. In contrast to TCR+ alpha beta cells differentiating in the thymus (from CD4+CD8+ precursors to CD4+CD8- or CD4-CD8+ progeny), TI IELs are not deleted by self-antigens, nor are they positively selected in the absence of the specific peptide. On the contrary, recognition of the antigen in the context of self-MHC is required for selection and granular differentiation of CD8+ TI IELs. Our results also show that, in contrast to the thymus, expression of the beta TG does not block expression of endogenous TCR gamma delta genes in TI IELs. The size of this gut IEL subpopulation and its difference in mechanisms of repertoire selection demonstrate the existence of a major extrathymic pathway of T-cell differentiation, the role of which remains to be elucidated.

Animals↗
PubMed1992

Different expression of the recombination activity gene RAG-1 in various populations of thymocytes, peripheral T cells and gut thymus-independent intraepithelial lymphocytes suggests two pathways of T cell receptor rearrangement.

The presence of transcripts of the recombination activating gene RAG-1 was studied by in situ hybridization on selected populations of murine thymocytes, peripheral lymphocytes and gut intraepithelial lymphocytes (IEL), obtained by cell sorting. RAG-1 mRNA was found in a majority of "double-positive" (DP) thymocytes, but was absent in "single-positive" thymocytes and peripheral T lymphocytes. The only other T lineages in which about 10%-20% of the cells contained RAG-1 mRNA, and in smaller amounts, were "double-negative" (DN), T cell receptor (TcR) gamma delta- cortical thymocytes and gut CD3- IEL. These observations suggest that (a) the high expression of RAG-1 transcripts in DP thymocytes is related to the process of expansion-selection of these cells, probably accompanied by repeated TcR rearrangements, and that (b) in contrast, CD3- IEL from the gut (which are thymus independent) as well as some DN thymocytes undergo limited TcR rearrangement giving rise locally to TcR+ T cells without prior extensive process of local expansion-selection. A small percentage of peripheral B cells also contained RAG-1 mRNA, raising the possibility that this protein may also be involved in immunoglobulin class switching.

Animals↗
PubMed1992

The extrathymic T-cell development pathway.

In normal mice, not all T-lineage cells are generated and selected in the thymus; an alternative, extrathymic, development pathway exists. Extrathymic T cells are rare in the spleen and lymph nodes, but are abundant in some tissues, such as the gut. Here, Benedita Rocha, Pierre Vassalli and Delphine Guy-Grand discuss the rules of selection of extrathymic T cells, assess the possible role of these cells in the defence of epithelial integrity and their potential role in autoimmune disease.

Animals↗
PubMed1991

Cytotoxic differentiation of mouse gut thymodependent and independent intraepithelial T lymphocytes is induced locally. Correlation between functional assays, presence of perforin and granzyme transcripts, and cytoplasmic granules.

Mouse gut intraepithelial lymphocytes (IEL), whether thymodependent (CD4+ or CD8 alpha/beta +; TCR-alpha/beta +) or thymoindependent (CD8 alpha/alpha +; TCR-alpha/beta + or -gamma/delta +), all display cytotoxic activity in a "redirected lysis assay" using anti-CD3 or anti-TCR beta or delta chains secreting hybridomas as targets; this is also observed with IEL of germ-free mice, indicating that this activity, which is absent in peripheral T lymphocytes, does not require stimulation by bacterial antigens. Perforin and granzyme transcripts are detectable in unselected gut IEL, in contrast to normal T lymphocytes of peripheral lymphoid organs. Cytological labeling (with [3H]DFP) of IEL smears reveals labeled granules (i.e., containing serine-esterases, presumably granzymes) in all subsets of gut IEL. This indicates that the gut micro-environment has an inductive role on the cytotoxic differentiation of lymphocytes of various origins when they reach the gut wall to become IEL.

Animals↗
PubMed1991

Two gut intraepithelial CD8+ lymphocyte populations with different T cell receptors: a role for the gut epithelium in T cell differentiation.

Mouse gut intraepithelial lymphocytes (IEL) consist mainly (90%) of two populations of CD8+ T cells. One bears heterodimeric alpha/beta CD8 chains (Lyt-2+, Lyt-3+), a T cell receptor (TCR) made of alpha/beta chains, and is Thy-1+; it represents the progeny of T blasts elicited in Peyer's patches by antigenic stimulation. The other bears homodimeric alpha/alpha CD8+ chains, contains no beta chain mRNA, and is mostly Thy-1- and TCR-gamma/delta + or -alpha/beta +; it is thymo-independent and does not require antigenic stimulation, as shown by its presence: (a) in nude and scid mice; (b) in irradiated and thymectomized mice repopulated by T-depleted bone marrow cells bearing an identifiable marker; (c) in thymectomized mice treated by injections of monoclonal anti-CD8 antibody, which lead to total depletion of peripheral CD8+ T lymphocytes; and (d) in germ-free mice and in suckling mice. In young nude mice, alpha/alpha CD8 chains, CD3-TCR complexes, and TCR mRNAs (first gamma/delta) are found on IEL, while they are not detectable on or in peripheral or circulating lymphocytes or bone marrow cells. IEL, in contrast to mature T cells, contain mRNA for the RAG protein, which is required for the rearrangement of TCR and Ig genes. We propose that the gut epithelium (an endoderm derivative, as the thymic epithelium) has an inductive property, attracting progenitors of bone marrow origin, and triggering their TCR rearrangement and alpha/alpha CD8 chains expression, thus giving rise to a T cell population that appears to belong to the same lineage as gamma/delta thymocytes and to recognize an antigenic repertoire different from that of alpha/beta CD8+ IEL.

Animals↗
PubMed1991

The V beta repertoire of mouse gut homodimeric alpha CD8+ intraepithelial T cell receptor alpha/beta + lymphocytes reveals a major extrathymic pathway of T cell differentiation.

Gut intraepithelial lymphocytes (IEL) contain two independent T cell receptor alpha/beta + T cell populations, with different V beta repertoires. In DBA/2 mice (Mlsa, IE+), the CD4+ and heterodimeric alpha/beta CD8+ thymodependent T cell pool shows the same deletion of V beta 6, 8.1, and 11+ cells as found in peripheral lymphoid organs. In contrast, such deletions are not observed in the pool of IEL bearing homodimeric alpha CD8+ chains, in which these V beta families are frequently observed in high amounts. The size of this gut homodimeric alpha CD8+ IEL pool and its different V beta repertoire selection demonstrate the existence of a major extrathymic pathway of T cell differentiation with a gut-restricted localization. The large amount of the thymo-independent, homodimeric alpha CD8+ IEL found in the small bowel may contribute to a first line of defense against exogenous superantigens.

Animals↗
PubMed1991

Intestinal intraepithelial lymphocytes.

Recent data on phenotype, differentiation, and functions of intestinal intraepithelial lymphocytes (IEL) in rodents and in humans are reviewed in this article. IEL form a large population of activated T cells located at the interface between the body and the septic intestinal content. Phenotypic studies indicate that IEL are mainly CD8-positive cells that contain both TCR alpha beta and TCR gamma delta cells in variable proportion depending on the species and antigenic intraluminal stimulation. Studies in experimental models suggest a dual origin, both thymus-dependent and thymus-independent of IEL, and a role of the gut epithelium in the differentiation of IEL. Functional studies allow insight on the mechanisms by which IEL can protect the intestinal epithelium or conversely, when abnormally activated, induce epithelial damage.

Animals↗
PubMed1990

Subsets of CD3+ (T cell receptor alpha/beta or gamma/delta) and CD3- lymphocytes isolated from normal human gut epithelium display phenotypical features different from their counterparts in peripheral blood.

Intestinal intraepithelial lymphocytes (IEL) were studied, after isolation in humans, for their surface antigens with a large variety of monoclonal antibodies. They show peculiar characteristics when compared with peripheral blood lymphocytes and intestinal lamina propria lymphocytes. Although a majority of human intraepithelial lymphocytes (IEL) express an alpha/beta type of T cell receptor (TcR), 13% express a gamma/delta TcR, a percentage which was significantly higher than that found in blood and in lamina propria. In contrast to observations in mice, there was no evidence that normal human TcR gamma/delta+ intestinal IEL might use preferential variable segments of gamma genes. About 10% of human intestinal IEL expressed the alpha chain but not the beta chain of CD8, thus resembling a subset of CD8 alpha+beta- IEL, which was recently described in mice and found to be of thymoindependent origin. In addition, 10% of human IEL had a unique phenotype of immature T cells, as they bore only CD7, but no other T cell or natural killer cell markers. Finally, even the major population of IEL which expressed the usual markers of the T cell lineage (CD3, TcR alpha/beta, CD2, CD4 or CD8 alpha/beta) differed from peripheral blood T lymphocytes by their peculiar expression of surface antigens associated with activation. Indeed, 80% of IEL were CD45R0+, CD45A-, but co-expression of CD11a, CD29 and LFA-3 was inconstant. In addition, 90% of IEL expressed HML-1.

Antigens, CD↗
PubMed1990

Classification of intractable diarrhea in infancy using clinical and immunohistological criteria.

Several experimental studies have demonstrated that activated intestinal T cells can induce villous atrophy. This observation led us to examine the possible role of activated T cells in the pathogenesis of intestinal lesions in a group of 13 children with intractable diarrhea and villous atrophy of unknown origin. Immunohistochemical study showed signs of intestinal mononuclear cell activation in seven patients. These signs included a marked increase in the number of mucosal T cells, mainly TCR alpha beta+, the appearance of lamina propria interleukin-2-receptor-bearing cells, and an increased expression of HLA-DR antigens by enterocytes. No local cause of intestinal T-cell activation was found. However, four out of seven patients had extradigestive symptoms of autoimmunity, suggesting that the intestine might also be the site of an autoimmune reaction responsible for the epithelial lesions. In these patients, presence of crypt necrosis and colic extension of the lesions suggested poor prognosis. In contrast, in six other patients, no immunohistochemical evidence of mucosal T-cell activation was obtained. In the latter cases, analysis of clinical data favored the hypothesis of a primary inborn defect of enterocyte differentiation.

Atrophy↗
PubMed1990

Role of in vivo activated T cells in the mechanisms of villous atrophy in humans: study of allograft rejection.

Four children aged 6 months to 9 years received fully HLA-mismatched ABO identical small intestinal allografts. In order to monitor the rejection process and to study epithelial changes induced by intestinal T cells activated by an allogeneic reaction, iterative biopsies were performed through the ileal enterostomy and processed for histology and immunohistochemistry. Episodes of acute histological reaction were observed in all 4 patients between day 10 and 160. It was preceded by appearance of pericryptic CD3+CD4+ or CD8+ T cells of recipient origin, increasing numbers of which expressed CD25. Simultaneously, early epithelial changes were noted: increased HLA-DR expression by enterocytes and decreased mitotic rate as shown by decreased numbers of KI67+ cells in crypts. During acute histological rejection, massive infiltration of mucosa by CD25+CD3+ T-cells and activated macrophages (KIM6+CD25+), was associated with crypt necrosis and then, destruction of surface epithelium. Successful treatment of graft rejection episodes with antilymphocytic serum (2), anti-CD3 monoclonal antibody (2), anti-CD25 monoclonal antibody (1) resulted in a rapid decrease of CD3+ cells, a more progressive decrease of CD25+ and KIM6+ macrophages, reappearance of KI67+ cells in crypts followed after a variable delay by recovery of villous architecture. Chronic histological rejection was observed in 1 patient after 7 months. It was characterized by total villous atrophy, fibrosis, endarteritis, infiltration of lamina propria and epithelium by CD3+CD8+ cells, a small number of which CD25+, strong HLA-DR expression by crypt and surface epithelium, increased numbers of KI67 enterocytes. Altogether these data suggested that activated T cells can induce two types of villous atrophy.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrophy↗