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C L Sentman

Publications and source records attributed to C L Sentman.

35 records · Page 2Linked to original sources
PubMed1996

Cloning of minimally divergent allelic forms of the natural killer (NK) receptor Ly-49C, differentially controlled by host genes in the MHC and NK gene complexes.

We have investigated whether expression of Ly-49C, detected by the mAb SW5E6, is subject to similar regulation by host MHC as is Ly-49A. Ly-49C expression was regulated by host MHC differentially in mice of A/Sn (A) and C57BL/6 (B) origin. Analysis of AXB recombinant inbred strains suggested two loci regulating the expression, one segregating with the NK gene complex and the other with the MHC. In MHC congenic strains, the A form of Ly-49C had a low expression level and was further down-regulated in the presence of the H-2b haplotype (very low). The B form of Ly-49C had a high expression level and was down-regulated in the presence of H-2Kk (medium). To test the hypothesis that the Ly-49C receptor in A/Sn and C57BL/6 mice may be differentially regulated by MHC products because they represent allelic forms, cDNAs for Ly-49C were cloned by reverse-transcriptase PCR from A/Sn and C57BL/6 mouse strains. The Ly-49C sequences from the two strains differed by six nucleotides leading to four predicted amino acid changes. Both cDNAs could be detected by the Ly-49C-specific Ab when expressed in EL-4 cells. Thus, like Ly-49A, Ly-49C expression is regulated by MHC class I molecules. Furthermore, A/Sn and C57BL/6 mice express different forms of Ly-49C that are down-regulated by different MHC class I molecules.

Alleles↗
PubMed1996

H-2Dp transgene alters natural killer cell specificity at the target and effector cell levels. Comparison with an H-2Dd transgene.

The expression of MHC class I molecules is an important determinate of natural killer (NK) cell specificity. The missing self hypothesis proposes that NK cells express receptors for self-MHC class I molecules so that target cells that share MHC class I alleles with the NK cells are not killed by those NK cells. However, some effector cells fail to kill some allogeneic target cells suggesting that shared motifs between different MHC class I alleles can interact with the effector cell class I receptors and prevent lysis. We have used transgenic mice to critically assess whether different MHC class I alleles can exert common influences on NK cell specificity at the host/effector and target cell levels. The specificity of NK cells have been compared between C57BL/6 (H-2b) mice and B6DP (H-2b, H-2Dp) and D8 (H-2b, H-2Dd) transgenic mice. The data indicate that H-2Dp and H-2Dd confer similar protection and specific lysis, such that NK cells from either of the H-2Dp or H-2Dd transgenic mice kill nontransgenic target cells yet they do not kill either of the transgenic target cells. The expression of an H-2Dp transgene also provides protection for C57BL/6 lymphoblasts from allogeneic BALB/c (H-2d) NK cells. Furthermore, H-2Dp and H-2Dd transgenic target cells are lysed to a similar extent by H-2k effector cells. These data suggest that H-2Dp and H-2Dd may be able to inhibit the same NK cell population. This may occur through a shared motif recognized by the same receptor, or different motifs recognized by different, but co-expressed receptors.

Animals↗
PubMed1996

Influence of glycosylphosphatidylinositol-linked H-2Dd molecules on target cell protection and natural killer cell specificity in transgenic mice.

The expression of certain major histocompatibility complex (MHC) class I ligands on target cells is one important determinate of their susceptibility to lysis by natural killer (NK) cells. NK cells express receptor molecules that bind to MHC class I. Upon binding to their MHC class I ligand, the NK cell is presumed to receive a signal through its receptor that inhibits lysis. It is unclear what role the MHC class I molecules of the effector and target cells play in signaling to the NK cell. We have investigated the role of the cytoplasmic and transmembrane domains of MHC class I molecules by producing a glycosylphosphatidylinositol (GPI)-linked H-2Dd molecule. The GPI-linked H-2Dd molecule is recognized by H-2Dd-specific antibodies and cytotoxic T lymphocytes. Expression of the GPI-linked H-2Dd molecule on H-2b tumor cells resulted in protection of the tumor cells after transplantation into D8 mice (H-2b, H-2Dd) from rejection by NK cells. In addition, NK cells from mice expressing the GPI-linked H-2Dd molecule as a transgene were able to kill nontransgenic H-2b lymphoblast target cells. The GPI-linked MHC class I molecule was able to alter NK cell specificity at the target and effector cell levels. Thus, the expression of the cytoplasmic and transmembrane domains of MHC class I molecules are not necessary for protection and alteration of NK cell specificity.

Animals↗
PubMed1995

Peripheral T-cell lymphoma in lckpr-bcl-2 transgenic mice.

t(14;18) is the most common translocation in human lymphoid malignancy and results in bcl-2 overexpression. Bcl-2 blocks apoptosis and constitutes the initial member of a new category of oncogenes, ie, regulators of cell death. Bcl-2-Ig transgenic mice develop follicular hyperplasia and progress to malignant B-cell lymphoma. To assess the oncogenic potential of bcl-2 in the T-cell lineage, a cohort of 68 lckpr-bcl-2 transgenic mice and 56 control littermates were monitored for signs of malignancy over a 24-month period. Eighteen (26%) lckpr-bcl-2 mice developed diffuse, predominantly large-cell lymphomas at a mean age of 18 months. In contrast, only one nontransgenic control mouse developed lymphoma. CD3 surface expression and clonal T-cell receptor beta rearrangements support the T-lineage classification of these neoplasms. lckpr-bcl-2-enforced lymphomas are predominantly CD4+CD8-, consistent with a mature peripheral T-cell phenotype. These data provide support for the thesis that violation of homeostasis through the repression of cell death can be a primary mechanism of tumorigenesis in multiple lineages.

Animals↗
PubMed1995

Altered phenotype and function of natural killer cells expressing the major histocompatibility complex receptor Ly-49 in mice transgenic for its ligand.

The Ly-49 molecule has been shown to interact with major histocompatibility complex (MHC) class I molecules, and the lytic function of Ly-49+ natural killer (NK) cells from C57BL/6 (H-2b) mice is inhibited by the recognition of H-2Dd on tumor target cells. Introduction of a Ly-49 ligand, H-2Dd, into C57BL/6 mice did not alter the percentage of Ly-49+ NK cells (13-18%), but it led to three functional effects on this subset. (i) The Ly-49 expression in the positive population was reduced by 30-50% compared to C57BL/6 control mice. (ii) While this Ly-49+ subset (Ly-49lo) in the transgenic mice failed to kill BALB/c concanavalin A (Con A) blasts, which have high H-2Dd expression, it was capable of killing SP2/0 tumor cells, which have low H-2Dd expression. Ly-49+ NK cells (Ly-49hi) from nontransgenic mice failed to kill both of these H-2Dd-expressing target cells. (iii) In the transgenic mice, the Ly-49+ subset acquired the ability to kill C57BL/6 Con A blasts, in contrast to the Ly-49+ NK cells of C57BL/6 mice. We propose a "receptor-calibration" hypothesis, where low receptor density on the effector cells imposed by selection or adaptation to the environment allows higher sensitivity for detection of reduced self-MHC ligands on potential target cells.

Animals↗
PubMed1995

Glycosylphosphatidylinositol-linked Db does not induce an influenza-specific cytotoxic T lymphocyte response or recycle membrane-bound peptides.

Major histocompatibility complex (MHC) class I molecules, as well as MHC class I-bound peptides, are known to recycle between the cell surface and an undefined, endosomal-like compartment. Little is known about the functional significance of this process. We have explored this using two different forms of the H-2Db molecule expressed in transgenic mice, either transmembranous (Db-tm) or with a glycophosphatidylinositol (GPI)-lipid anchor (Db-GPI). The recycling capacity of peptides bound to Db-tm and Db-GPI was investigated using glycosylated Db-binding glycopeptides, which were detected by flow cytometry. Only the tm form of Db was found to readily internalize and recycle glycopeptides to the cell surface. When transgenic mice were immunized with influenza A virus (PR8) strain and tested for cytotoxic T lymphocyte (CTL) responses against an immunedominant nucleoprotein epitope (366-374, ASNENMETM), only Db-tm mice were found to generate specific CTL responses. The results support the idea that membrane recycling of MHC class I-bound peptides on antigen-presenting cells may be important for the generation of certain CTL responses.

Animals↗
PubMed1995

Inhibition of natural killer cell-mediated bone marrow graft rejection by allogeneic major histocompatibility complex class I, but not class II molecules.

The role of major histocompatibility complex (MHC) class I and class II molecules in natural killer (NK) cell-mediated rejection of allogeneic, semisyngeneic and MHC-matched bone marrow grafts was investigated. The use of beta 2-microglobulin (beta 2m) -/- and beta 2m +/- mice as bone marrow donors to MHC-mismatched recipients allowed an analysis of whether the presence of semi-syngeneic and allogeneic MHC class I gene products would be triggering, protective or neutral, in relation to NK cell-mediated rejection. Loss of beta 2m did not allow H-2b bone marrow cells to escape from NK cell-mediated rejection in allogeneic (BALB/c) or semi-allogeneic (H-2Dd transgenic C57BL/6) mice. On the contrary, it led to stronger rejection, as reflected by the inability of a larger bone marrow cell inoculum to overcome rejection by the H-2-mismatched recipients. In H-2-matched recipients, loss of beta 2m in the graft led to a switch from engraftment to rejection. At the recipient level, loss of beta 2m led to loss of the capability to reject H-2-matched beta 2m-deficient as well as allogeneic grafts. When MHC class II-deficient mice were used as donors, the response was the same as that against donors of normal MHC phenotype: allogeneic and semi-syngeneic grafts were rejected by NK cells, while syngeneic grafts were accepted. These data suggest a model in which allogeneic class I molecules on the target cell offer partial protection, while certain syngeneic class I molecules give full protection from NK cell-mediated rejection of bone marrow cells. There was no evidence for a role of MHC class II molecules in this system.

Animals↗
PubMed1995

Missing self recognition by natural killer cells in MHC class I transgenic mice. A 'receptor calibration' model for how effector cells adapt to self.

It is now clear that NK cells can perform 'missing self' recognition, that is eliminate cells because these fail to express certain critical MHC class I products adequately. Although isolated NK cell subsets can be turned off by self as well as non-self MHC molecules, genetic studies, mainly in vivo, argue that NK cells always learn to spare cells expressing critical self MHC alleles. This article reviews work on receptor expression and specificity of NK cells in MHC class I transgenic mice. A 'receptor calibration' model is proposed to account for how NK cells can interact with self as well as non-self MHC and adapt their receptors to perform optimally to detect alterations of self MHC.

Animals↗
PubMed1994

H-2 allele-specific protection from NK cell lysis in vitro for lymphoblasts but not tumor targets. Protection mediated by alpha 1/alpha 2 domains.

In vivo murine NK cells are known to mediate graft rejection in allogenic as well as in "F1 anti-parental" situations. We have studied an in vitro system based on rIL-2-activated spleen cells and Con A lymphoblast targets in relation to the genetics of F1 hybrid resistance and NK cell activity. We demonstrate that NK cells in this in vitro model are regulated by MHC class I genes in an allele-specific manner at the level of the effector and the target. Using rIL-2-activated effector cells from nude C57BL/6 (B6) and BALB/c mice, we observed no killing of MHC syngeneic lymphoblasts. However, B6 as well as BALB/c lymphoblasts were killed by effector cells from allogeneic nude mice as well as by cells from (BALB/c x B6)F1 hybrids. Experiments that used D8 mice (which carry an H-2Dd transgene on B6 background) and beta 2-m-/- mice demonstrated a direct role for MHC class I molecules at the effector as well as at the target cell level: H-2Dd transgenic effector cells with the typical NK phenotype 3A4+/CD8- killed B6 blasts, but expression of the corresponding H-2Dd transgene in the target lymphoblasts protected them from killing. By using transgenic mice carrying exon shuffled MHC class I transgenes, the protective effect of the H-2Dd molecule was mapped to the alpha 1/alpha 2 domains. MHC class I-deficient lymphoblasts from beta 2-m-/- mice were killed by effectors from all strains of mice, including those matched for MHC. The H-2 class I allele-specific protection in this in vitro assay was observed for lymphoblasts but not for tumor cells, despite the fact that these tumor cells are protected in an allele-specific manner in vivo.

Animals↗
PubMed1993

Expression of the Bcl-2 protein in murine and human thymocytes and in peripheral T lymphocytes.

Bcl-2, a proto-oncogene that can block apoptosis, was found to be expressed throughout the thymic medulla, but in only scattered cells in the thymic cortex. In order to determine the precise distribution of Bcl-2 protein during thymocyte development, we utilized mAb specific for either mouse or human Bcl-2. Thymocyte subpopulations were assessed using three-color flow cytometry and a saponin-permeabilization method. Staining of adult mouse and human thymocytes was comparable, with 20 to 35% of cells expressing Bcl-2. Bcl-2 was expressed in nearly all CD4+ and CD8+, and CD3hi cells, but in only 5 to 10% of CD4+8+ cells. The CD4-8- population was more variable, with 25 to 40% of human cells and 65 to 80% of murine cells expressing Bcl-2. In sorted adult murine CD4-8- cells, the very immature Pgp-1+/IL-2R alpha- subset had a high percentage of Bcl-2+ cells. Bcl-2 expression was also examined during murine fetal development. At fetal day 15.5 to 16.5, 60 to 70% of total thymocytes expressed Bcl-2. By fetal day 17.5, overall Bcl-2 expression fell to adult levels of 20 to 30%. Bcl-2 was present in peripheral T cells from lymph node, spleen, and peripheral blood at uniformly high levels. In vitro stimulation with anti-CD3 or anti-TCR antibodies increased Bcl-2 expression in total thymocyte cultures, but could not induce Bcl-2 expression in CD4+8+ cells, even with the addition of a variety of cytokines. These data suggest that early double negative thymocytes express Bcl-2 but lose Bcl-2 with differentiation to the double positive stage. Thymocytes regain Bcl-2 during selection to a single positive state and retain Bcl-2 in the periphery.

Animals↗
PubMed1991

bcl-2 inhibits multiple forms of apoptosis but not negative selection in thymocytes.

The vast majority of cortical thymocytes die during T cell development while those that survive this selective process accumulate in the medulla. bcl-2, an inner mitochondrial membrane protein, has been shown to inhibit apoptosis in certain cell lines. In the thymus, bcl-2 is regionally localized to the mature T cells of the medulla. To assess the role of bcl-2 in the programmed death of thymocytes, we generated transgenic mice that redirected bcl-2 expression to cortical thymocytes. bcl-2 protected immature CD4+8+ thymocytes from glucocorticoid, radiation, and anti-CD3-induced apoptosis. Moreover, bcl-2 altered T cell maturation, resulting in increased percentages of CD3hi and CD4-8+ thymocytes. Despite this, clonal deletion of T cells that recognize endogenous superantigens still occurred. This transgenic model indicates that multiple death pathways operate within the thymus that can be distinguished by their dependence on bcl-2.

Animals↗
PubMed1991

Rejection of bone marrow cell allografts by natural killer cell subsets: 5E6+ cell specificity for Hh-1 determinant 2 shared by H-2d and H-2f.

The 5E6 antigen, defined by anti-5E6 mAb, is expressed on one-half of murine natural killer (NK) cells, and we have previously demonstrated (C. L. Sentman et al., J. Exp. Med. 1989. 170: 1991) that 5E6+ NK cells are necessary for the rejection of BALB/c (Hh-1d) but not C567BL/6 (Hh-1b) bone marrow cells (BMC). In experiments described here, we have characterized the specificity of 5E6+ and 5E6- NK cell subsets for hemopoietic histocompatibility-1 (Hh-1) antigens. Prospective recipient mice were treated with anti-5E6 mAb and challenged with BMC from a variety of donors. In addition, H-2d/Hh-1d C.B-17 scid 5E6+ or 5E6- NK cells were adoptively transferred into irradiated, NK cell-depleted hosts and challenged with H-2b/Hh-1b BMC. The data indicate that the 5E6+ NK cells are necessary for the rejection of only those BMC that express the Hh-1 determinant 2 shared by H-2d and H-2f haplotypes of strains BALB/c (d), A.Ca (f), and B10.M (f). No reactivity to other Hh-1 antigens resides in the 5E6+ population. In contrast, the ability of NK cells to lyse H-2d or H-2b tumor cells was independent of 5E6 expression. These results suggest that the 5E6 molecule is likely to be important in the specific recognition and rejection of BMC that express Hh-1 determinant 2, and is probably not involved in recognition of "tumor target cell structures".

Animals↗
PubMed1989

Identification of a subset of murine natural killer cells that mediates rejection of Hh-1d but not Hh-1b bone marrow grafts.

NK cells demonstrate many immune functions both in vitro and in vivo, including the lysis of tumor or virus-infected cells and the rejection of bone marrow allografts. However it remains unclear whether or not all NK cells can mediate these various functions or if NK cells exist in functionally distinct subsets. We have developed a new NK-specific mAb, SW5E6, which binds to approximately 50% of murine NK cells. The 5E6 antigen identifies a distinct and stable subset of NK cells and is expressed on about one-half of fresh or rIL-2-activated murine NK cells. Both 5E6+ and 5E6- NK cells are capable of lysing YAC-1 tumor cells in vitro and in vivo. By treating animals with SW5E6, we demonstrate that the 5E6+ subset is necessary for the rejection of H-2d/Hh-1d but not H-2b/Hh-1b bone marrow cells. Thus NK cells exist as functionally separable subsets in vivo.

Animals↗
PubMed1989

Effector cell expression of NK1.1, a murine natural killer cell-specific molecule, and ability of mice to reject bone marrow allografts.

The rejection of Hh-1 incompatible bone marrow cells in irradiated mice is mediated by NK cells and is genetically regulated. We tested the role of the NK-specific gene, NK1.1, in regulating the rejection of allogeneic bone marrow cell grafts. NK1.1+ mice, that are known to display strong resistance against Hh-1 incompatible grafts, were crossed to H-2/Hh-1 identical NK1.1-, poor responder mice, and the progeny were backcrossed to the poor responder parent. The segregating mice were individually typed for their expression of NK1.1 and the ability to resist Hh-1 incompatible bone marrow cells (BMC). A strong correlation was noted between expression of NK1.1 and rejection of H-2d/Hh-1d BMC. Our results support the idea that NK1.1 is one of the genes responsible for strong resistance to Hh-1d (determinant 2) but not for Hh-1j (determinant 3) BMC grafts. We suggest that the NK1.1 molecule functions as an accessory molecule in the cellular interactions involving the recognition of Hh-1 determinants.

Animals↗
PubMed1989

Pan natural killer cell monoclonal antibodies and their relationship to the NK1.1 antigen.

The study of natural killer (NK) has been difficult because they account for a small percentage of peripheral blood and splenic lymphocytes and the paucity of NK specific antigens that have been identified. We have isolated pure populations of C57BL/6 (H-2b) NK cells using the IgG2b monoclonal antibody PK136 (anti-NK1.1). These NK1.1+ cells were used to immunize 129/J (H-2b) mice, and in this report, we describe three new NK specific monoclonal antibodies (SW3A4(IgM), SW4B12(IgG1), and SW2B4(IgG2b] and their relationship to the known murine NK antigen NK1.1. We have further characterized the NK1.1 antigen as a 39 kd molecule which is coded for by a gene which appears to map to chromosome 6.

Animals↗
PubMed1988

Kinetics and location of bone marrow cell graft rejection by irradiated mice.

Natural killer (NK) cells were eliminated with rabbit anti-Asialo GM1 (anti-ASGM1) serum to test the kinetics and location of bone marrow cell (BMC) rejection. Anti-ASGM1 serum was injected intravenously in mice at various times before or after irradiation (8.6 Gy) and transfer of parental-strain or allogeneic BMC. Growth of BMC was determined by measuring splenic 5-iodo-2'-deoxyuridine-125I incorporation 5 days after cell transfer. Anti-ASGM1 serum weakened hybrid resistance even if injected intravenously as late as 24 h post-BMC transfer and even in recipients injected with polyinosinic:polycytidylic acid so as to boost NK activity. If regenerating spleen cells (higher rate of cell cycling) were used as donor cells instead of BMC, the length of time required for rejection was unaffected. Anti-ASGM1 serum injected intravenously rapidly inhibited splenic NK activity and lung clearance of YAC-1 tumor cells, but when injected intratracheally, it only inhibited lung NK activity. Thus, BMC rejection occurs in the hematopoietic tissue and requires at least 24 h.

Animals↗