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D H Raulet

Publications and source records attributed to D H Raulet.

At least 73 records · Page 4Linked to original sources
PubMed1994

Multiple natural killer cell-activating signals are inhibited by major histocompatibility complex class I expression in target cells.

Several lines of evidence indicate that major histocompatibility complex class I molecules expressed by target cells can prevent natural killer cell (NK) lysis, possibly by engaging inhibitory receptors expressed by NK cells. On the other hand it is likely that NK cells must be activated to lysis by the recognition of unidentified NK target structures on target cells. To investigate the relationship between positive activation of NK cells by NK target structures versus inhibition by target cell class I molecules, we have examined various NK/target cell interactions for which the expression of inhibitory class I molecules by the target cells is known. The results suggests that specific properties of the target cell other than the absence of class I expression are necessary to activate NK-mediated lysis. Furthermore, different effector cell populations, i.e. freshly isolated versus interleukin-2 activated NK cells, differ in their capacity to kill class I-deficient lymphoblast target cells. In general, class I-deficient target cells that are resistant to direct lysis by a given NK population can be lysed by the NK cells when the reaction is mediated by antibody-dependent cellular cytotoxicity (ADCC). Most significantly, all types of NK-mediated lysis of lymphoblasts, of tumor cells and of almost any target by ADCC can be inhibited by appropriate class I gene expression in the target cell. These results suggest a model in which lysis by NK cells must be triggered by any one of a set of distinct target cell ligands, but that all of these signals can be overruled by class I-mediated inhibition.

Animals↗
PubMed1994

MHC class I-deficient mice.

A great deal has already been learned from the analysis of beta 2m-mutant mice, but it is clear that a great deal remains to be learned. A significant (though unanticipated) problem with this model system is that it is functionally leaky: residual functional class I expression can be detected in beta 2m- mice, and small numbers of functional CD8+ lymphocytes are present in the animals. In many cases, this has frustrated the initial attempts at obtaining immediate definitive resolution of important questions regarding the function of class I molecules. This has occurred primarily in instances in which the class I-deficient mice fail to express an expected phenotype--for example, in studies showing that beta 2m- mice make adequate protective immune responses against certain intracellular pathogens, and are able to reject some allogeneic tissues with a relatively normal pace. On the other hand, it appears that combining the use of beta 2m- mice with other methods (for example, antibody-mediated depletion of CD8+ T cells) is usually adequate to circumvent these difficulties. It remains to be seen whether other better class I deficiencies can be engineered--for example, large deletions of class I genes or mutations in transcription factors essential for class I gene expression. The extent of immunocompetence of beta 2m- mice was somewhat surprising. It was widely expected that class I-deficient mice would be exquisitely sensitive to many viral infections, though the results indicate that sensitivity varies dramatically with the virus and conditions of infection. However, it appears that in lieu of one major arm of the immune system, compensatory immune mechanisms are in many cases able to deal with infection. Similar conclusions are developing from the analysis of several other recently generated mutant mice. Nevertheless, the results indicate a very important role for class I-directed responses in clearing infections mediated by various viral and parasitic agents, particularly in the case of more severe conditions of infection. Although the class I-deficient mice were initially considered primarily a vehicle for analysis of the role of CD8+ T cells, evidence is accumulating that they manifest deficiencies in several other types of lymphocytes, including NK cells, TCR alpha beta+CD4-CD8- cells, and a subset of TCR gamma delta+ cells. This has been a boon for analysis of the development of these cells, but at the same time it has created difficulties in assigning a biological effect of the mutation to a specific lymphocyte deficiency.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

CD28-induced costimulation of T helper type 2 cells mediated by induction of responsiveness to interleukin 4.

Type 1 and type 2 cloned T helper (Th) cells are believed to require different antigen-presenting cell (APC)-derived costimuli for proliferation. In the case of Th1-cloned T cells, CD28 signaling costimulates production of autocrine interleukin 2 (IL-2). Th2 cells produce their autocrine growth factor, IL-4, without costimulation, but require APC-derived costimuli, or IL-1, to respond to IL-4. Here we demonstrate that engagement of CD28 on Th2 cells with anti-CD28 antibody or with APC-associated B7 costimulates Th2 responsiveness to IL-4 but does not affect IL-4 or IL-2 production by Th2 cells. Costimulation of Th2 cells via CD28 appears to involve the induction of IL-1 production by Th2 cells, which acts in an autocrine fashion to induce IL-4 responsiveness. These results suggest that CD28-induced costimulation plays an important role in responses mediated by both types of Th cells.

Animals↗
PubMed1993

The role of viral enhancer "core" motif-related sequences in regulating T cell receptor-gamma and -delta gene expression.

T cells express clonally distributed alpha beta or gamma delta Ag receptor heterodimers. Transcriptional enhancers for the genes of all four subunits are active in both gamma delta and alpha beta T cells, but are less active or inactive in other cells. Conserved sequence motifs are present in all four enhancers, suggesting that common transcription factors regulate TCR gene expression. One of these motifs in the gamma 3 site of the TCR-gamma enhancer is similar to motifs found in several other lymphoid-specific and viral enhancers. This conserved "core" sequence is present in the enhancers of Moloney and SL3-3 murine leukemia viruses, important for transcription in T cells and in determining disease specificity. Here we characterize the gamma 3 site of the gamma enhancer and a corresponding homologous site, delta E3, of the TCR-delta enhancer. Our results suggest that the core site is critical for activity of the 200-bp gamma enhancer fragment and of the gamma 3 and delta E3 sites. Furthermore, we identify a nuclear factor in human T cell lines that specifically binds the core region in these and several other core-containing enhancers. This factor may be identical to or related to a purified bovine nuclear core binding factor that binds the core region of the Moloney murine leukemia virus enhancer, gamma 3 and delta E3 sites, suggesting that similar proteins regulate the TCR-gamma, delta and Moloney murine leukemia virus enhancers. Other sequences in the gamma 3 site upstream of the core sequence are also critical for activity in T cells, suggesting that at least two different factors are required for functional activity of the gamma 3 site.

Animals↗
PubMed1993

Selection is not required to produce invariant T-cell receptor gamma-gene junctional sequences.

Recombination of V-, D- and J-gene segments can generate an enormous diversity of T-cell antigen receptor (TCR) gene sequences. Although many gamma delta T cells fully exploit this diversification process, those in the epidermal and vaginal epithelium do not, predominantly expressing invariant gamma delta receptors in which the V-(D)-J junctional sequences in almost all the productive rearrangements are identical. The almost exclusive use of identical TCRs by cells in these sites is thought to reflect recognition of a stress-induced autologous antigen. To explain the prevalence of the invariant junctional sequences, it has been proposed that thymic selection operates on a population of originally diverse progenitor cells, resulting in a homogeneous repertoire. Alternatively the invariant sequences may result from biases in the recombination machinery in the fetal thymic progenitors of these cells. We report here the use of mice into which mutated TCR gamma-gene rearrangement substrates have been introduced as transgenes to demonstrate directly that the canonical TCR V gamma 3-J gamma 1 and V gamma 4-J gamma 1 sequences occur at high frequency in the absence of the possibility of selection for the protein products.

Animals↗
PubMed1993

Ordered rearrangement of variable region genes of the T cell receptor gamma locus correlates with transcription of the unrearranged genes.

T cell receptor V gamma genes rearrange to the J gamma 1 gene segment in a highly ordered fashion during development. We demonstrate a striking correlation between the pattern of expression of unrearranged V gamma genes and the timing of their rearrangement. Thus, the increases in V gamma 2 rearrangements, and decreases in V gamma 3 and V gamma 4 rearrangements observed during development are paralleled by increasing or decreasing levels of the corresponding unrearranged V gene transcript. We also provide evidence that both the V gamma 3 and V gamma 4 genes are accessible in mature V gamma 3+ cells, but that the V gamma 4 gene may be inaccessible in the progenitors of V gamma 3 cells. The results suggest that regulated local accessibility of the chromatin surrounding V gamma genes is responsible for ordered V gamma gene rearrangement during development.

Animals↗
PubMed1992

Expression of the Mls-1a superantigen results in an increased frequency of V beta 14+ T cells.

Minor lymphocyte-stimulating (Mls) Ag are alloantigens that stimulate T cells expressing specific V beta regions. Recent studies have established that Mls Ag are examples of endogenous superantigens encoded by the products of endogenous mouse mammary tumor virus (MLV) genomes. In a mouse strain that expresses a given mammary tumor virus (Mls) Ag, reactive T cells expressing the corresponding V beta region are profoundly deficient, due at least in part to clonal deletion of the cells during their development. Expression of Mls and other endogenous superantigens, therefore, results in profound alterations in the ultimate repertoire of T cells in an animal. A role for endogenous superantigens in positive selection of T cells has not been previously established. Here we present evidence that expression of Mls-1a leads to a specific increase in the abundance of V beta 14+ T cells. Genetic studies indicate linkage of the effect to the Mls-1a gene. Neonatal tolerance studies argue against the possibility that the increase is due solely to the deletion of Mls-reactive V beta 14- T cells. The results are consistent with the Mls-1a product playing a role in the positive selection of V beta 14+ T cells.

Animals↗
PubMed1992

CD28-mediated signalling co-stimulates murine T cells and prevents induction of anergy in T-cell clones.

Occupancy of the T-cell antigen receptor is insufficient to induce T-cell activation optimally; a second co-stimulatory signal is required. Exposure of T-cell clones to complexes of antigen with major histocompatibility complex molecules in the absence of the co-stimulatory signal induces a state of clonal anergy. This requirement for two stimuli for T-cell activation could have an important role in vivo in establishing peripheral tolerance to antigens not encountered in the thymus. The receptor on T cells required for the co-stimulatory stimulus involved in the prevention of anergy has not been identified. The human T-cell antigen CD28 provides a signal that can synergize with T-cell antigen receptor stimulation in activating T cells to proliferate and secrete lymphokines. Here we report that a monoclonal antibody against the murine homologue of CD28 (ref. 7; J.A.G. et al., manuscript in preparation) can provide a co-stimulatory signal to naive CD4+ T cells and to T-cell clones. Moreover, we demonstrate that this co-stimulatory signal can block the induction of anergy in T-cell clones.

Animals↗
PubMed1991

Identification of a T-cell-specific transcriptional enhancer located 3' of C gamma 1 in the murine T-cell receptor gamma locus.

A transcriptional enhancer element has been localized 3 kilobases 3' of the murine T-cell receptor C gamma 1 locus using a chloramphenicol acetyltransferase reporter gene construct. As a monomer the enhancer functions only in PEER gamma delta cells and Jurkat alpha beta cells of the T-cell lines tested. However, a tetramer of the enhancer functions in virtually all T-cell lines tested, including alpha beta T-cell lines, but not in other cell types. These results suggest that elements other than the enhancer are responsible for the failure of rearranged C gamma 1 genes to be expressed in alpha beta T cells. The enhancer has been localized to a 200-base-pair Rsa I restriction fragment, which contains sequence motifs similar to those found in the other T-cell receptor enhancers but not in the immunoglobulin enhancers.

Animals↗
PubMed1990

Beta 2-microglobulin deficient mice lack CD4-8+ cytolytic T cells.

Mice homozygous for a beta 2-microglobulin gene disruption do not express any detectable beta 2-m protein. They express little if any functional major histocompatibility complex (MHC) class I antigen on the cell surface yet are fertile and apparently healthy. They show a normal distribution of gamma delta, CD4+8+ and CD4+8- T cells, but have no mature CD4-8+ T cells and are defective in CD4-8+ T cell-mediated cytotoxicity. Our results strongly support earlier evidence that MHC class I molecules are crucial for positive selection of T cell antigen receptor alpha beta+ CD4-8+ T cells in the thymus and call into question the non-immune functions that have been ascribed to MHC class I molecules.

Animals↗
PubMed1990

Expression of the V beta 5.1 gene by murine peripheral T cells is controlled by MHC genes and skewed to the CD8+ subset.

We have examined the usage of the V beta 5.1 region in peripheral T cell populations of several mouse strains by measuring V beta 5.1 transcript levels. The results show that V beta 5.1 is expressed predominantly by CD8+ T cells in mice of several MHC haplotypes. This finding suggests that V beta 5.1 may confer restriction to class 1 molecules present in these strains. Interestingly, however, T cells expressing V beta 5.1, like those expressing V beta 17a and V beta 11, are clonally deleted from both CD4 and CD8 subsets in mice that express MHC IE molecules. The latter result implies that V beta 5.1 confers reactivity to a class 2 molecule (IE). These results are discussed in terms of positive selection and clonal deletion. Finally we provide evidence that genes in the K or A regions of the MHC also control V beta 5.1 usage.

Animals↗
PubMed1990

Selective expression of V delta 6 genes by B2A2- CD4- CD8- T cell receptor gamma/delta thymocytes.

Most CD4-CD8- adult murine thymocytes characterized by absence of the B2A2 (J11d) antigen express T cell receptors (TcR) alpha/beta and utilize preferentially V beta 8.2 segments. To a much lesser extent, B2A2-CD4-CD8- thymocytes also express TcR gamma/delta, as evidenced by biochemical and Northern blot analysis. We have now been able to exclude the possibility that these cells might co-express both types of TcR: V beta 8+ B2A2- CD4-CD8- thymocytes expressed no TcR delta mRNA whereas the corresponding V beta 8- subset transcribed full-length TcR gamma as well as delta mRNA. Furthermore, the TcR gamma/delta expressing B2A2- thymocytes were found to use preferentially V delta 6 genes. Conversely, they did not express V delta 5 genes which are most frequently used by other TcR gamma/delta-bearing populations such as B2A2+ CD4-CD8- thymocytes or CD4-CD8- peripheral lymph node cells. RNase protection experiments showed that two particular V delta 6 transcripts predominate in these gamma/delta populations, the most prominent V delta 6 sequence being highly homologous if not identical to V alpha 7.1. Our observations extend previous information on overlapping V alpha and V delta gene repertoires, particularly in the cross-hybridizing V alpha 7/V delta 6 gene family. Moreover, our data suggest that B2A2-CD4-CD8- thymocytes represent a developmentally unique subset in which both V delta and V beta segments are nonrandomly expressed.

Animals↗
PubMed1990

Expression of human adenosine deaminase in mice reconstituted with retrovirus-transduced hematopoietic stem cells.

Recombinant retroviruses encoding human adenosine deaminase (ADA; adenosine aminohydrolase, EC 3.5.4.4) have been used to infect murine hematopoietic stem cells. In bone marrow transplant recipients reconstituted with the genetically modified cells, human ADA was detected in peripheral blood mononuclear cells of the recipients for at least 6 months after transplantation. In animals analyzed in detail 4 months after transplantation, human ADA and proviral sequences were detected in all hematopoietic lineages; in several cases, human ADA activity exceeded the endogenous activity. These studies demonstrate the feasibility of introducing a functional human ADA gene into hematopoietic stem cells and obtaining expression in multiple hematopoietic lineages long after transplantation. This approach should be helpful in designing effective gene therapies for severe combined immunodeficiency syndromes in humans.

Adenosine Deaminase↗
PubMed1990

The immunobiology of gamma delta+ T cells.

T cells expressing the gd receptor are the major lymphocyte type represented in intraepithelial layers of various organs in the mouse. The gd cells found in distinct anatomical locations express distinct restricted subsets of Vg and Vd genes. Cells in each site are probably derived from progressive intrathymic waves of gd cells expressing these restricted V gene subsets. These features of the cells suggest a role in monitoring epithelial layers for distinctive ligands, and recent studies implicate mycobacterial "stress proteins' as antigens for g/d T cells. Thus gd T cells may represent an arm of the immune system devoted to elimination of infected, transformed or otherwise stressed autologous epithelial cells, based on recognition of induced stress proteins. They may also be devoted to mycobacterial immunity by virtue of specificity for mycobacterial stress proteins and other antigens.

Animals↗
PubMed1989

IL-6 and IL-1 synergize to stimulate IL-2 production and proliferation of peripheral T cells.

Purified T cells can be induced to proliferate and to produce the autocrine growth factor IL-2 with mAb to the TCR and costimulatory cytokines. In a previous report we demonstrated that human IL-6 stimulates IL-2 production and proliferation of purified T cells, in conjunction with the insolubilized anti-TCR V beta 8 mAb, F23.1. Here we show that when CD4+ T cells are rigorously purified to greater than 99% CD4+CD8-, they respond only weakly to F23.1 and IL-6. Instead, there is an additional requirement for IL-1, which dramatically synergizes with IL-6 to induce prolonged (greater than 7 days) proliferative responses and IL-2 production. Similar results were observed when the highly mitogenic anti-CD3 mAb 145-2C11 was substituted for F23.1. The proliferation induced by F23.1, IL-1, and IL-6 was substantially (greater than 80%) inhibited by a mAb to mouse IL-2, and was not inhibited by an anti-IL-4-mAb. In accordance with this finding, medium conditioned by the activated CD4+ cells contained large amounts of IL-2, which increased over a 7-day culture period. These results demonstrate that IL-6 and IL-1 stimulate T cell proliferation by inducing production of the autocrine growth factor IL-2. In addition, the two lymphokines must be present simultaneously for activation to occur. The possible roles of IL-6 and IL-1 in IL-2 gene regulation and in Ag-induced T cell activation are discussed.

Adjuvants, Immunologic↗