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D M Pardoll

Publications and source records attributed to D M Pardoll.

At least 91 records · Page 5Linked to original sources
PubMed1990

Interleukin-2 production by tumor cells bypasses T helper function in the generation of an antitumor response.

A poorly immunogenic murine colon cancer was used to investigate mechanisms of antitumor immunity. Injection of tumor cells engineered by gene transfection to secrete IL-2 stimulated an MHC class I-restricted cytolytic T lymphocyte (CTL) response against the parental tumor. The tumor cells secreting IL-2 produced an antitumor response in vivo, even in the absence of CD4+ T cells. Animals immunized with the engineered cells were protected against subsequent challenge with the parental tumor cell line. Similar findings were demonstrated for other tumor types. Thus, provision of a helper lymphokine in a paracrine fashion induced a tumor-specific immune response involving activation of endogenous CTLs and other immune effector cells. These findings demonstrate that the failure of an effective antitumor immune response may be primarily due to a helper arm deficiency of the immune system rather than a paucity of tumor-specific cytotoxic effector cells. Furthermore, they outline a novel strategy for augmenting tumor immunity.

Animals↗
PubMed1990

A murine thymocyte clone expressing gamma delta T cell receptor mediates natural killer-like cytolytic function and TH1-like lymphokine production.

The murine CD4- CD8- (double negative, DN) thymocyte cell line and clones expressing T cell receptor gamma delta chains in association with CD3 complex have been established and characterized. This line and a representative clone (DN7.12.11) which appear to derive from the minor population of CD3+ DN thymocytes can be stimulated to proliferate and to produce lymphokines by anti-CD3 or anti-Thy-1 antibodies or calcium ionophore plus phorbol ester. Autocrine proliferation is dependent on binding of interleukin (IL)2 to functional IL2 receptor. Upon stimulation, these cells produce IL2 and IFN-gamma but not IL4, resembling conventional CD4+ TH1 cells in this regard. The cloned line also mediates spontaneous cytolysis against a variety of tumor targets without regard for the presence of conventional major histocompatibility complex molecules on the target cell surface. Blocking and modulation experiments suggest that target recognition by the gamma delta/CD3 complex is not involved in the spontaneous lysis, resembling natural killer (NK) cells. The results suggest that gamma delta +DN T cells are able to have mature functions such as NK-like cytotoxicity and lymphokine secretion as peripheral gamma delta +T cells. They also provide a possible role of gamma delta + DN thymocytes in establishing a intrathymic environment for differentiation and selection of alpha beta-expressing T cells.

Animals↗
PubMed1990

Are the IL-2 receptors expressed in the murine fetal thymus functional?

It is well established that the majority of murine fetal thymocytes (day 15 of gestation) express receptors for interleukin 2 (IL-2), but the functional significance of these IL-2 receptors (IL-2Rs) is not clear. In situ hybridization data show a developmentally regulated expression of IL-2 and IL-2R mRNA. IL-2 binding studies were performed on fetal thymocytes and the results show the presence of both high (kD approximately equal to 20 pM) and low (kD approximately equal to 10 nM) affinity IL-2Rs. These IL-2Rs are indeed functional: intact fetal thymic lobes (but not cell suspensions) cultured in IL-2 exhibited an in vitro proliferative response at 20 pM of IL-2, corresponding with the presence of a functional high-affinity IL-2R on fetal thymocytes. The IL-2-dependent growth was primarily observed in the IL-2R+ thymic subset, which contains the CD3-/CD4-/CD8- precursor thymocytes. Furthermore, in vitro blocking of IL-2 in intact fetal thymic lobes resulted in a reduction in the cell yield, which predominantly affected the expansion of the immature CD3-/CD4-/CD8- thymocytes. Our findings strongly support the concept that the IL-2/IL-2R pathway is responsible for the proliferation of precursor cells within the fetal thymus.

Animals↗
PubMed1990

Molecular mechanisms for lineage commitment in T cell development.

Thymocyte development is characterized by the ordered expression of T cell receptors as well as the accessory molecules, CD4 and CD8. Interactions of these critical surface molecules with MHC ligands expressed on thymic stromal cells mediate additional developmental processes. Now that the stages of thymic differentiation have been delineated, current investigations are addressing the mechanisms that underlie T cell lineage commitment and selection.

Animals↗
PubMed1989

Activation of gamma delta T cells in the primary immune response to Mycobacterium tuberculosis.

Although the immunologic role of T cells bearing the conventional alpha beta T cell receptor (TCR) has been well characterized, little is known about the function of the population of T cells bearing the gamma delta TCR. Therefore, the role of gamma delta T cells in the immune response to Mycobacterium tuberculosis (MT) was investigated. The number of TCR gamma delta cells in the draining lymph nodes of mice immunized with MT was greatly increased in comparison with the number of TCR alpha beta cells. Three biochemically distinct gamma delta TCRs were detected. Analyses of cell cycle, of interleukin-2 receptor expression, and of interleukin-2 responsiveness showed that a large proportion of the gamma delta T cells were activated in vivo. TCR gamma delta cells responded to solubilized MT antigens in vitro but, in contrast to MT-specific alpha beta T cells, the response of gamma delta T cells to MT did not require major histocompatability complex class II recognition. These results provide an example of antigen-specific activation of gamma delta T cells in vivo and indicate that gamma delta T cells may have a distinct role in generating a primary immune response to certain microorganisms.

Animals↗
PubMed1988

Effects of cyclosporine A on T cell development and clonal deletion.

Cyclosporine A (CsA) is an important immunosuppressive drug that is widely used in transplantation medicine. Many of its suppressive effects on T cells appear to be related to the inhibition of T cell receptor (TCR)-mediated activation events. Paradoxically, in certain situations CsA is responsible for the induction of a T cell-mediated autoimmunity. The effects of CsA on T cell development in the thymus were investigated to elucidate the physiologic events underlying this phenomenon. Two major effects were revealed: (i) CsA inhibits the development of mature single positive (CD4+8- or CD4-8+) TCR-alpha beta+ thymocytes without discernibly affecting CD4-8- TCR-gamma delta+ thymocytes and (ii) CsA interferes with the deletion of cells bearing self-reactive TCRs in the population of single positive thymocytes that do develop. This suggests a direct mechanism for CsA-induced autoimmunity and may have implications for the relative contribution of TCR-mediated signaling events in the development of the various T cell lineages.

Animals↗
PubMed1988

Deletion of self-reactive thymocytes occurs at a CD4+8+ precursor stage.

As T cells develop in the thymus, they become tolerant of self-antigens. A major advance in the understanding of how this process occurs was the direct demonstration that cells bearing autoreactive T-cell receptors (TCRs) are physically eliminated from the population of functionally mature T cells present in both the thymus and periphery. We have sought to determine the developmental stage at which autoreactive T cells are eliminated by examining the expression of V beta 17a anti-I-E TCRs under various experimental conditions. In vivo antibody blockage of the CD4 molecule on developing thymocytes of I-E+ C57BR mice was found to inhibit the deletion of V beta 17a-bearing cells from the CD4-8+ single positive thymocyte subset. This result provides strong evidence that deletion of potentially autoreactive T cells occurs at a CD4+8+ precursor stage, that the non-clonally distributed accessory molecules (CD4, CD8) are significant participants in the self-recognition process that leads to clonal elimination, and that thymic class II major histocompatibility complex (MHC) molecules can influence the repertoire of CD4-8+ cells.

Animals↗
PubMed1988

Thymus-dependent and thymus-independent developmental pathways for peripheral T cell receptor-gamma delta-bearing lymphocytes.

To elucidate the developmental pathways of T cells that bear TCR gamma delta, we have analyzed the kinetics of expression and biochemical characteristics of gamma delta receptors in the thymus and spleen of normal and athymic (nude) mice, as well as nude mice engrafted with neonatal thymuses. TCR gamma delta-bearing thymocytes and splenocytes have a CD4-8- phenotype, and both populations express products of the C gamma 1 locus. TCR gamma delta-bearing cells develop in the thymus before their appearance in the spleen. Young nude mice have no detectable TCR gamma delta-bearing cells in their spleens. When young nude mice are given thymus grafts, TCR gamma delta-bearing cells of host origin first develop in the engrafted thymus, followed by their appearance in the spleen. In the absence of a thymus graft, the spleens of old nude mice eventually develop small numbers of TCR gamma delta + cells, as well as TCR alpha beta + cells. These results demonstrate that there is a major thymic-dependent pathway for TCR gamma delta expression, as well as a minor thymic-independent pathway seen in older nude mice. The development of TCR gamma delta + cells in the thymus before their appearance in the spleen, both in normal ontogeny as well as in the thymus-engrafted nude mouse model, suggests that thymic TCR gamma delta + cells are precursors of the thymus-dependent population of peripheral TCR gamma delta + cells.

Aging↗
PubMed1988

Proliferation and production of IL-2 and B cell stimulatory factor 1/IL-4 in early fetal thymocytes by activation through Thy-1 and CD3.

To examine which cell surface molecules can operate as transducers of activation signals to early fetal thymocytes, we analyzed the ability of mAb to CD3 and Thy-1 to induce fetal thymocyte activation. Both proliferation and lymphokine secretion were used as measures of activation. We show that anti-CD3 antibodies induce activation of fetal thymocytes as early as day 13 of fetal thymus development, 2 days before CD3 can be detected by flow cytometry. In addition, an alternative activation signal can be delivered to fetal thymocytes through the Thy-1 molecule as early as it is expressed, i.e., day 13. Both CD3- and Thy-1-mediated activation of day 15 fetal thymocytes results in expansion of cells expressing a CD3-gamma delta receptor complex; no CD3-alpha beta receptor complex could be detected. IL-2 production induced by CD3- and Thy-1-induced activation of fetal thymocytes is evident at the 13th day of gestation. Finally, an additional lymphokine B cell stimulatory factor-1 (BSF-1)/IL-4 (so far known only to be produced by mature CD3- cells), is also produced by fetal thymocytes. The results demonstrate that at least two cell surface molecules, Thy-1 and CD3, can function as pathways of activation in fetal thymocytes, and that at least two lymphokines, IL-2 and BSF-1/IL-4, are produced upon activation. These findings may well reflect a role for the early appearance of CD3- cells in thymus ontogeny.

Animals↗
PubMed1988

T cell receptor gamma/delta chain diversity.

The TCR-gamma and -delta chains of six murine hybridomas were compared by one-dimensional SDS-PAGE and two-dimensional NEPHGE/SDS-PAGE analysis. This allowed the identification of three distinct gamma chains (gamma a, gamma b, and gamma c) and three distinct delta chains (delta a, delta b, and delta c). Four gamma/delta chain combinations (gamma a delta a, gamma b delta b, gamma b delta c, and gamma c delta a) were observed. These results indicate that multiple forms of the delta chain are expressed and suggest that the delta chains are encoded for by an Ig-like rearranging gene. This delta chain polymorphism significantly enhances the potential diversity of TCR-gamma/delta, which may be of importance for a better understanding of the putative ligand(s) recognized by this receptor.

Animals↗
PubMed1988

Activation properties of T cell receptor-gamma delta hybridomas expressing diversity in both gamma- and delta-chains.

To elucidate the structure, diversity, and activation properties of the murine T3-associated gamma delta-receptor, examination was made of the gamma delta and T3 components, T cell receptor (TCR) gene transcription, activation properties, and lymphokine production in a panel of four cloned T cell hybridomas expressing a TCR-gamma delta. Biochemical analysis of the gamma and delta proteins expressed on these hybridomas reveals new gamma and delta species not observed in whole populations of dLy-1 Lyt-2-L3T4-thymocytes from which these hybridomas were derived. Thus, analysis of expression of the TCR-gamma delta complex at the clonal level indicates that both gamma and delta appear to be expressed as multiple distinct gene products within a homozygous inbred mouse strain. Northern blot analysis reveals that, whereas all gamma delta hybridomas had mature 1.5-kb TCR-alpha-chain and mature TCR-gamma-chain transcripts, none had mature 1.3-kb TCR-beta-chain transcripts, thus indicating that the type of TCR heterodimer expressed reflects of the state of TCR gene transcription in these hybridomas. Our results also reveal striking similarities between TCR-gamma delta and TCR-alpha beta cells with respect to their activation properties. First, all five of the T3 components associated with the gamma delta-complex are of the same size and have the same glycosylation patterns as those associated with alpha beta-heterodimers. Second, induction of function in these gamma delta cells (assayed by lymphokine production) can be achieved with a variety of stimuli known to elicit activation signals in alpha beta cells as well: direct receptor-engagement (i.e., through anti-Thy-1), and phorbol 12-myristate 13-acetate-plus-ionomycin-mediated. Collectively, these findings suggest that gamma delta T cells express a receptor of at least limited diversity and use T3-mediated activation pathways very similar to those employed by TCR-alpha beta-bearing T cells.

Animals↗
PubMed1987

Early genetic events in T cell development analyzed by in situ hybridization.

In situ hybridization was used to investigate the expression of T cell receptor (TCR) alpha, beta, and gamma mRNAs in developing fetal and adult precursor thymocytes. gamma transcription was observed at the earliest time tested (day 12), followed by beta 12 h later, and TCR alpha on day 16. The early beta transcripts appeared to be from unrearranged or incompletely rearranged (D-J-C) beta loci. V beta region transcription was first detectable on day 14 and transcription of different V beta genes was induced at different times. These results delineate a schedule sequence of TCR gene activation, which begins within 1 d after entry of stem cells into the fetal thymus.

Animals↗
PubMed1987

Carrier detection in X-linked agammaglobulinemia by analysis of X-chromosome inactivation.

We used a recently developed strategy to analyze patterns of X-chromosome inactivation in human cell populations in order to study female members of families with X-linked agammaglobulinemia--i.e., to detect the carrier state and to test the hypothesis that the disorder results from a defect intrinsic in the development of B cells. According to this strategy, recombinant-DNA probes simultaneously detect restriction-fragment-length polymorphisms and patterns of methylation of X-chromosome genes. Random X-inactivation patterns were observed in isolated peripheral-blood granulocytes, T lymphocytes, and B lymphocytes of women who were not carriers. In contrast, one of the two X chromosomes was preferentially active in the peripheral B cells, but not the T cells or granulocytes, of three carriers of the disorder. This observation strongly supports the hypothesis that X-linked agammaglobulinemia results from an intrinsic defect in B-cell development. Moreover, the analysis described here can be used for direct identification of carriers in families with this disease.

Agammaglobulinemia↗
PubMed1987

Analysis of T-cell receptor gamma chain expression in the thymus.

While much is known about the structure and function of the T-cell receptor (TCR) alpha beta heterodimer, information has just begun to emerge about the gamma protein, the product of a third rearranging T-cell receptor gene. We describe the use of antiserum to a carboxy-terminal peptide common to several of the murine gamma chain constant regions and a monoclonal antibody to the murine T3 complex to identify products of this T-cell receptor gene family in a subpopulation of Lyt2-, L3T4- thymocytes. The gamma chain has a molecular weight of 35kD, is disulfide bonded to a 45kD partner termed delta (delta) and is associated with the T3 complex. The cells that bear this second T-cell receptor appear to represent a distinct lineage differentiating within the thymus.

Animals↗
PubMed1987

Molecular events in the induction of a nonresponsive state in interleukin 2-producing helper T-lymphocyte clones.

Exposure of normal interleukin 2 (IL-2)-producing helper T-cell clones to antigen and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide-treated antigen-presenting cells results in proliferative unresponsiveness to subsequent stimulation with antigen and normal antigen-presenting cells. In the present study, we have examined the molecular events that accompany the induction of this unresponsive state. T cells stimulated in this manner failed to produce IL-2, but interleukin 3, interferon-gamma, and IL-2 receptors were partially induced and T-cell receptor beta mRNA was fully induced. Although T-cell unresponsiveness correlated with an IL-2 production defect, addition of IL-2 during the induction phase failed to prevent development of the unresponsive state. The critical biochemical event appeared to be an increase in intracellular calcium. Removal of calcium from the medium prevented induction of the unresponsive state, whereas addition of the calcium ionophore ionomycin induced unresponsiveness as well as all of the related partial activation events. Thus, an increase in intracellular calcium under nonmitogenic conditions appears to initiate an alternative activation program that prevents the T cell from producing IL-2 in response to subsequent normal activation signals. The significance of this in vitro model for tolerance induction in vivo is discussed.

Animals↗
PubMed1987

The unfolding story of T cell receptor gamma.

Antigen-specific, major histocompatibility complex-restricted recognition by classical T cells is mediated by a T cell receptor (TCR) consisting of a disulfide-linked alpha beta heterodimer. During the search for the genes encoding the alpha and beta proteins, a third immunoglobulin-like gene, termed gamma, was uncovered. Like the TCR alpha and beta genes, the TCR gamma gene consists of variable and constant segments that rearrange during T cell development in the thymus. Although the physiological role of TCR gamma remains an enigma, much has been learned with the recent identification of the protein products of this gene family in both mice and humans. The gamma chain is associated with a partner chain, termed delta. The gamma delta heterodimer is associated with an invariant T3 complex, very similar to that associated with the alpha beta heterodimer, and appears predominantly, if not exclusively, on cells with a CD4-, CD8- phenotype both in the thymus and in the periphery. TCR gamma delta is the first T3-associated receptor to appear during thymocyte development and defines a separate T cell lineage distinct from alpha beta-bearing cells. Although TCR alpha beta-bearing cells and TCR gamma delta-bearing cells follow parallel developmental pathways, the diversity of expressed gamma delta receptors is extremely limited relative to that of alpha beta receptors.

Alleles↗