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Biomedical subjects

P Marrack

Publications and source records attributed to P Marrack.

At least 127 records · Page 7Linked to original sources
PubMed1989

Reactivity of V beta 17a+ CD8+ T cell hybrids. Analysis using a new CD8+ T cell fusion partner.

Tolerance to IE molecules leads to deletion of V beta 17a-bearing T cells. Both, the CD4+ as well as the CD8+ T cell subsets are affected. A large percentage of CD4+ V beta 17a+ T cell hybrids recognize IE molecules. We now have investigated the reactivity for IE antigens of CD8+ V beta 17a+ T cell hybrids. Using a transfection approach, we have introduced the murine CD8 molecule into different V beta 17a+ T cell hybrids. Furthermore, the CD8 cDNA was transfected into the BW5147 alpha-beta- fusion partner. This allowed us to generate a large number of V beta 17a+ T cell hybrids by fusion with the appropriate T cells. Only 6% of T cell hybrids were stimulated to produce IL-2 upon incubation with IE+ cells. However, in those, the CD8 molecule seemed not to contribute to the IE reactivity of the hybrid, since mAbs against the CD8 molecule failed to inhibit their reactivity. This low percentage of V beta 17a+ CD8+ IE-reactive T cell hybrids contrasts with the strong reduction of CD8+ V beta 17a+ T cells in IE+ mice, strongly suggesting that elimination of such cells in the thymus occurs when they are coexpressing CD4 and CD8. This view was confirmed by the occasional expression of CD4 in some hybrids in which case IE reactivity was detected. Furthermore, we demonstrated the functional integrity of the introduced CD8 molecule by: (a) reconstitution of the IL-2 response in a class I-restricted TNP-specific T cell hybrid; and (b) by generation of alloreactive class I-restricted T cell hybrids using the new CD8+ fusion cell line. This CD8+ fusion partner, BWLyt2-4, should prove useful to study antigen processing and antigen presentation requirements of class I-restricted T cells.

Animals↗
PubMed1989

The thymus has two functionally distinct populations of immature alpha beta + T cells: one population is deleted by ligation of alpha beta TCR.

During T cell development, the processes of selection and tolerance act on the universe of expressed T cell receptors in the thymic cortex to form the repertoire of mature T cells that will respond to foreign antigen in the context of self-MHC in that animal. We have subdivided the cortical thymocytes into three functionally distinct populations: one population which is antigen-receptor negative, a second population which is antigen-receptor positive and is resistant to deletion by signaling through the antigen receptor, and a third population which is also antigen-receptor positive but is sensitive to deletion. These results have implications for the cellular compartments in which positive and negative selection occur and for the biochemical mechanisms that mediate selection and tolerance.

Animals↗
PubMed1989

Two better cell lines for making hybridomas expressing specific T cell receptors.

Two variants of the AKR thymoma BW5147 have been isolated which can no longer express functional TCR alpha- and beta-chains. By generating hybridomas with these variant fusion lines, TCR of any normal T lymphocyte, including TCR-gamma/delta, can be studied at a clonal level, without interference of the BW5147-derived receptor chains. In this study one of the variants has been useful in identifying the reactivity to allogeneic MHC Ag of BW5147 itself.

Amino Acid Sequence↗
PubMed1989

V beta-specific stimulation of human T cells by staphylococcal toxins.

The staphylococcal toxins are responsible for a number of diseases in man and other animals. Many of them have also long been known to be powerful T cell stimulants. They do not, however, stimulate all T cells. On the contrary, each toxin reacts with human T cells bearing particular V beta sequences as part of their receptors for major histocompatibility complex protein-associated antigen. The specificity of these toxins for V beta s puts them in the recently described class of superantigens and may account for the differential sensitivity of different individuals to the toxic effects of these proteins.

Antibodies↗
PubMed1989

Analysis of V beta 17a expression in new mouse strains bearing the V beta a haplotype.

A set of new mouse strains were produced that carry the V beta a haplotype of the TCR-alpha/beta and any of a number of different H-2 haplotypes on backgrounds derived from related C57BL, C57L, and C57BR mice. Study of V beta 17a expression in these mice confirms the association between the presence of IE and the deletion of V beta 17a+ T cells. A second H-2 gene causing deletion of V beta 17a+ T cells was mapped in these mice to the K end of H-2k, and H-2 influences on the level of selection of CD4+ V beta 17a+ T cells were indicated.

Animals↗
PubMed1989

Evidence that Mls-2 antigens which delete V beta 3+ T cells are controlled by multiple genes.

V beta 3+ T cells are eliminated in Mls-2a mice carrying some, but not all, H-2 types. Analysis of AKXD and BXD recombinant inbred strains showed that Mls-2a (formerly Mlsc) was not the product of a single gene and suggested that at least two non-H-2 genes control V beta 3 levels. Studies of the progeny of a B10.BR x (C3H/HeJ x B10.BR)F1 backcross confirmed the existence of two V beta 3+ T cell deleting genes: one unlinked and one linked to Ly-7, which we propose be called Mls-2 and Mls-3, respectively. Mls-2a induces partial deletion of V beta 3+ T cells with a bias toward deleting CD4+ cells. It stimulates V beta 3+ hybrids and may be linked to Mtv-13 on chromosome 4. A third non-H-2 gene is implicated in enhancing the presentation of Mls-2a. Mls-3a causes elimination of all V beta 3+ T cells in H-2k and H-2d mice but poorly stimulates V beta 3+ hybrids.

Animals↗
PubMed1989

Alpha beta T cell receptor and CD3 transduce different signals in immature T cells. Implications for selection and tolerance.

Ligand binding to alpha beta TCR has different consequences in thymocytes at different developmental stages, causing alternatively positive selection, clonal deletion, or activation. These various functional consequences may be due to changes in the signaling properties of the receptor complex during development. In this report we show that alpha beta TCR engagement on immature thymocytes has different effects on intracellular free calcium concentrations than alpha beta TCR engagement on mature T cells. In contrast, CD3 engagement on immature thymocytes and mature T cells has the same effect on intracellular free calcium, suggesting that altered signal transduction in immature thymocytes may be due to inefficient alpha beta TCR-CD3 coupling. These studies also suggest that in certain T cell populations, activation events resulting from ligation of CD3 may not accurately reflect the activation events resulting from ligation of the physiologic receptor, alpha beta TCR.

Animals↗
PubMed1989

Characterization of a monoclonal antibody which detects all murine alpha beta T cell receptors.

Research on the specificities, functions, and maturation of T cells would be greatly aided by a collection of monoclonal antibodies which distinguishes different types of TCR. With this end in mind hamsters were immunized and tested for production of pan-reactive anti-mouse alpha beta TCR antibodies. In this report we describe the properties and uses of a mAb, H57-597, produced from one of these animals. The mAb reacts with surface receptors on all alpha beta TCR-bearing cells and does not react with receptors on gamma delta+ T cells. In an immobilized form, this antibody can directly activate T cells bearing alpha beta TCR. It can be used in immunoprecipitation reactions to precipitate receptor from the appropriate cell types. In combination with anti-CD3, the antibody can be used in cytofluorographic analyses to measure numbers of CD3+, alpha beta+, and CD3+, gamma delta+ cells in the thymus and periphery.

Animals↗
PubMed1989

Influence of the major histocompatibility complex on positive thymic selection of V beta 17a+ T cells.

A monoclonal antibody was used to show directly positive thymic selection of the T cell repertoire in mouse strains expressing the 17a beta-chain variable domain (V beta 17a) of the T cell receptor. In the absence of the potent tolerizing class II major histocompatibility complex (MHC) molecule, I-E, peripheral expression of V beta 17a+ T cell receptors varied with the MHC haplotype of the mouse strain. In the most extreme case, H-2q mice expressed high peripheral levels of CD4+ V beta 17a+ T cells (14 to 19 percent), whereas H-2b mice expressed low levels (3 to 4 percent). Analysis of (b x q)F1 mice and chimeric mice showed that these differences were determined by positive thymic selection and implicated the thymic epithelium as the controlling cell type.

Animals↗
PubMed1989

Presentation of antigen, foreign major histocompatibility complex proteins and self by thymus cortical epithelium.

In mouse and man most peripheral T cells bear clonally variable receptors made up of alpha- and beta-chains which bind ligands on target cells consisting of peptide fragments of foreign antigens, complexed with cell surface proteins encoded by the major histocompatibility complex (MHC) of the individual. In the thymus, developing T cells are selected to mature only if their receptors will be able to participate in self-MHC plus antigen recognition in the periphery. This positive selection occurs in the presence of self-MHC, but in the apparent absence of antigen, leading to the paradoxical conclusion that developing thymocytes must be positively selected by engagement of their receptors and self-MHC alone, although thymocytes that react too well with self-MHC are eliminated. To account for this, it has been suggested that MHC molecules in the thymus are not identical to those found elsewhere. To test this and other hypotheses, we have examined the ability of the presumed selecting cells, those of the thymus cortical epithelium, to present various MHC complexes to T cells. Our results indicate that MHC molecules on thymus epithelium are not always the same as those found elsewhere.

Animals↗
PubMed1989

The V beta-specific superantigen staphylococcal enterotoxin B: stimulation of mature T cells and clonal deletion in neonatal mice.

Staphylococcal enterotoxin B is known to be a powerful T cell stimulant in mouse and man. In this paper we show that, for mice, this is because the protein in association with major histocompatibility complex class II molecules stimulates virtually all T cells bearing V beta 3 and V beta 8.1, 8.2, and 8.3, and few others. Neonatal mice given the enterotoxin eliminate all mature, and some immature, T cells bearing these V beta s, demonstrating that tolerance to exogenously administered antigen can be caused by clonal deletion of reactive T cells. The enterotoxin shares these "superantigenic" properties with known self-antigens in mice, Mls-1a and Mls-2a, and a B cell-derived product, a shared property that is unlikely to be coincidental or inconsequential.

Animals↗
PubMed1988

The structure of V alpha and J alpha segments in the mouse.

Antigen receptors on most T-cells are heterodimeric glycoproteins, comprised of an alpha chain and a beta chain. These chains are encoded by discontiguous variable (V), diversity (D) and joining (J) gene segments that rearrange to produce a contiguous and functional alpha or beta chain gene. To investigate the size and diversity of the germline repertoire of alpha-chain gene segments, we have characterized and sequenced 20 alpha chain cDNAs. Among these cDNA clones, we have found 4 J alpha and 4 V alpha sequences that have not yet been described. The relationship of these "new" gene segments to those already characterized is discussed.

Amino Acid Sequence↗
PubMed1988

Demethylated CD8 gene in CD4+ T cells suggests that CD4+ cells develop from CD8+ precursors.

Mature T cells and medullary thymocytes bear either the CD4 or CD8 differentiation antigen. Precursor cells in the thymus express neither CD4 nor CD8 (CD4-8-), but most cortical thymocytes are CD4+8+. Whether CD4+ and CD8+ mature T cells arise directly from CD4-8- precursors or from a CD4+8+ intermediate remains unresolved. In this study, methylation of the CD8 gene in murine T cells and thymocytes was examined. There was progressive demethylation of the CD8 gene in the thymus during the transition from CD4-8- to CD4+8+. A similar pattern of demethylation of the CD8 gene was seen in CD4+ mature T cells, suggesting previous expression of CD8 in the CD4+ lineage.

Animals↗
PubMed1988

B cells expressing Ig transgenes respond to a T-dependent antigen only in the presence of Ia-compatible T cells.

We sought a quicker and easier method for the isolation of B cells enriched for a given Ag specificity. Here, we report our results using transgenic mice bearing mu- and kappa-transgenes that encode an IgR against the hapten phosphorylcholine. Splenic B cells from such mice had a high percentage of phosphorylcholine-binding cells and differentiated in vitro in response to T cell hybridomas in an Ag-specific, Ia-restricted manner. Supernatants from such in vitro cultures could not transfer helper activity, nor could the T cell be replaced in other ways tried when using a classical T-dependent Ag. These results support the model of a cognate interaction between T and B cell, and we present evidence that the interaction may consist of two or more steps.

Animals↗