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W H Chambers

Publications and source records attributed to W H Chambers.

At least 55 records · Page 3Linked to original sources
PubMed1993

Interleukin 7-induced expression of specific T cell receptor gamma variable region genes in murine fetal liver cultures.

We previously reported that culture of murine fetal liver (FL) cells with interleukin 7 (IL-7) results in expression of high levels of T cell receptor (TCR) gamma transcripts by a population of cells expressing Thy-1 and Pgp-1, suggesting that IL-7 promotes the growth and/or differentiation of pre-T cells. We demonstrate herein that culture of FL cells for 7 d with IL-7 caused the rearrangement and expression of TCR gamma variable (V) region genes V gamma 4 and V gamma 6, but not V gamma 5 or V gamma 7. Since this effect was not blocked by hydroxyurea, it appeared to represent induction of expression of these genes by IL-7 rather than expansion of a preexisting positive population. We also show that IL-7 induced RAG-1 and RAG-2 mRNA expression by FL cells. These data provide evidence that specific TCR gamma/delta V region genes can be rearranged and expressed by T lineage cells before their migration to the thymus, in response to IL-7.

Animals↗
PubMed1993

Coexpression of NKR-P1 and alpha beta-TCR on lymphoid cells in fully xenogeneic (rat-->mouse) chimeras and syngeneically reconstituted (A-->A) rats.

We have identified three populations of cells among rat splenocytes expressing NKR-P1, including cells of NKR-P1bright/alpha beta-TCR-, NKR-P1dim/alpha beta-TCR+, and NKR-P1dim/alpha beta-TCR- phenotypes. To study the phenotypic characteristics and development of these various cell populations, we have made use of transplanting untreated rat bone marrow into recipient rats (syngeneic) or mice (fully xenogeneic) conditioned with total body irradiation. Rat NK cells exhibit normal phenotypic markers (NKR-P1+, CD8+) and are normally functional by 28 days after reconstitution. We have found that the various populations of NKR-P1+ cells are enriched significantly in the spleen and follow a characteristic pattern of development in the first mo after reconstitution. After syngeneic bone marrow reconstitution (rat-->rat), NKR-P1dim and NKR-P1bright cells (3-15%) can be demonstrated among splenocytes as early as day 3 after bone marrow transplantation. By day 7, the NKR-P1+ cells reach peak levels and comprise as much as 80% of splenic lymphoid cells, with 35% being NKR-P1bright and 45% being NKR-P1dim. The percentage of NKR-P1+ cells decreases over the next several wk until they constitute "normal rat" levels with 8 to 20% being NKR-P1bright and only 1 to 5% being NKR-P1dim. These same populations are also present in fully xenogeneic chimeras. In both models, approximately 80 to 90% of the NKR-P1dim cells were found to coexpress alpha beta-TCR at all time points. These NKR-P1dim/alpha beta-TCR+ cells are not large granular lymphocytes and lack NK cell lytic activity against YAC-1 target cells. Additional analyses of cells derived from spleen, bone marrow, and thymus indicated that NKR-P1+ cells develop, for the most part, in a thymic-independent manner in our fully xenogeneic chimeras and syngeneically reconstituted rats. At present the developmental pathway of these NKR-P1dim cells remains speculative.

Animals↗
PubMed1993

Degradation of enkephalins by rat lymphocyte and purified rat natural killer cell surface aminopeptidases.

Enkephalins have been reported to induce an elevation in natural killer (NK) cell cytolytic function. In the central nervous system, the short-lasting biological activity of the enkephalins may be attributable to their rapid hydrolysis at the cell surface. In a similar manner, a potential mechanism for regulating the effects of enkephalins on NK cells is through their degradation at the cell surface. The purpose of this study was to determine if NK cells were capable of enzymatically degrading Met- and Leu-enkephalin and to determine the type(s) of enzymes responsible. We report that rat nylon wool enriched splenocytes, purified NK cells, and interleukin-2 activated NK (A-NK) cells were capable of hydrolyzing the N-terminal Tyr residue from Met- and Leu-enkephalin as determined by high-performance liquid chromatography. The rate of Tyr cleavage from Met-enkephalin was approximately twice that of Leu-enkephalin for both splenocytes, NK, and A-NK cells. On a cellular basis, enkephalin degradation was four to five times greater with A-NK cells than with splenocytes. Only a Tyr cleavage product was detected, which suggested the possibility of an aminopeptidase activity. This was confirmed by the ability of bestatin, a specific inhibitor of cell surface aminopeptidases, to almost completely inhibit enkephalin degradation by splenocytes (85%) and A-NK cells (96%). A-NK cells were more sensitive to bestatin inhibition as indicated by their IC50 values (0.01 mM for splenocytes and 0.001 mM for A-NK cells). In addition, the chelator 1,10-phenanthroline was also capable of effectively inhibiting enkephalin degradation, suggesting that the enzyme responsible has the characteristics of a metalloprotease. In contrast to the effects of bestatin or phenanthroline, typical inhibitors of serine and thiol proteases were without effect.

Amino Acid Sequence↗
PubMed1992

Functional heterogeneity between NKR-P1bright/Lycopersicon esculentum lectin (L.E.)bright and NKR-P1bright/L.E.dim subpopulations of rat natural killer cells.

In this report, we present data on heterogeneity of rat NK cells utilizing a combination of antibody and lectin-binding characteristics. Among NKR-P1bright NK cells, two discrete populations characterized as Lycopersicon esculentum lectin (L.E.)bright (60 to 80%) and L.E.dim (20 to 40%) were identified by flow cytometry. Comparison of the morphology of sorted NKR-P1bright/L.E.bright and NKR-P1bright/L.E.dim cells indicated that both were greater than 90% LGL. An analysis of the functional capabilities of the sub-populations indicated that NKR-P1bright/L.E.bright NK cells were more efficient in lysis of YAC-1 target cells (1743 LU20/10(7) cells) than were NKR-P1bright/L.E.dim cells (504 LU20/10(7) cells). Conversely, NKR-P1bright/L.E.dim NK cells were much more efficient at lysis of antibody-sensitized erythrocytes (antibody-dependent cellular cytotoxicity (ADCC)) (1412 LU20/10(7) cells) than were NKR-P1bright/L.E.bright cells (165 LU20/10(7) cells). Lysis of antibody sensitized P815 target cells yielded similar results as NKR-P1bright/L.E.dim cells and NKR-P1bright/L.E.bright cells had 905 LU20/10(7) and 189 LU20/10(7), respectively. Additional experiments indicated that NKR-P1bright/L.E.bright NK cells had the capacity to trigger lytic activity via NKR-P1 whereas NKR-P1bright/L.E.dim NK cells did not. NKR-P1bright/L.E.bright sorted cells had a greater capacity to form conjugates with YAC-1 target cells than did NKR-P1bright/L.E.dim sorted cells. Conversely, NKR-P1bright/L.E.dim NK cells were demonstrated to form E-A rosettes whereas the NKR-P1bright/L.E.bright NK cells were not. Additional experiments indicated that tomato lectin itself was not responsible for the differences in reverse ADCC activity or ADCC activity among the subsets. However, lysis of YAC-1 target cells was modulated to some degree by the lectin. These data indicate that NKR-P1bright/L.E.bright and NKR-P1bright/L.E.dim subpopulations of rat NK cells have different capacities for: 1) triggering through NKR-P1; and 2) E-A rosette formation and lysis of antibody-sensitized target cells by ADCC.

Animals↗
PubMed1991

Natural killer cell cytolytic granule-associated enzymes. I. Purification, characterization, and analysis of function of an enzyme with sulfatase activity.

An enzyme with sulfatase activity has been isolated from the granules of a rat NK leukemia cell line, CRNK-16. The enzyme has been purified from crude preparation, with a specific activity of 52 nmol/min/mg of protein, by DEAE ion exchange and Con A-Sepharose affinity chromatography, resulting in a specific activity of 230 nmol/min/mg of protein. The molecular mass of the purified enzyme was estimated to be 40 kDa by gel filtration chromatography at pH 7.4, but the enzyme had the ability to complex to molecular masses of greater than 300 kDa at low pH when crude granule extract was used as the starting sample, suggesting that it associates with other granule components. The enzyme was determined to be an arylsulfatase by its ability to (a) hydrolyze p-nitrophenyl sulfate (Km = 26.0 mM) and p-nitrocatechol sulfate (pNC sulfate) (Km = 1.1 mM) and (b) be inhibited by sulfite (Ki = 6.0 x 10(-7) M), sulfate (Ki = 1 x 10(-3) M), and phosphate (Ki = 4 x 10(-5) M) in a competitive manner. The pH optimum for enzymatic activity was determined to be 5.6. The role of this enzyme in cytolytic function was investigated by examining the effect of its substrates and inhibitors on granule- and cell-mediated lysis. pNC sulfate was shown to cause a dose-dependent inhibition of target cell lysis by isolated cytolytic granules (complete inhibition at 12.5 mM). Sulfite induced an incomplete inhibition (50% at 1 mM), whereas phosphate was essentially without inhibitory effect. Sulfate, on the other hand, altered lytic activity in a biphasic manner, inasmuch as it induced an inhibition of lysis at high concentrations and an increase of lysis at low concentrations. Cell-mediated lysis was inhibited by pNC sulfate in a dose-dependent fashion at concentrations greater than 2.5 mM, with nearly complete inhibition at 50 mM. Sulfate also altered the lytic activity by intact cells in a biphasic manner, although the effect was much less pronounced. Sulfite and phosphate caused only a 30% inhibition of lytic activity. These results suggest that the sulfatase enzyme is involved in NK cytolytic function, presumably at the lethal hit stage.

Animals↗
PubMed1991

Sorting minor subpopulations of cells: use of fluorescence as the triggering signal.

Flow cytometric cell sorting is commonly used to obtain purified subpopulations of cells for use in in vitro and in vivo assays. This can be time-consuming if the subpopulations of interest represent very low percentages of the cell suspension under study. Often the desired subpopulations are identified by two-color immunofluorescence staining. Generally, cell sorting is performed with a flow cytometer configured to trigger on light scatter signals, then sort windows are set based upon the signals from both fluorescent markers. We demonstrate that triggering the cytometer with the fluorescence signal from antibody staining common to both of the desired subpopulations, then sorting the subpopulations based upon staining of a second marker, substantially increases the speed of cell sorting vis-à-vis traditional methods. This is because undesired events are not analysed, allowing an increase in the throughput rate. While desired subpopulations of cells can be obtained by this method, undesired (i.e., nonstaining) cell "contaminants" increase and may require a second sort. The combined time for the initial enrichment sort and a second sort can be less than sorting once using standard methodology. Alternatively, the degree of contamination may be controlled by adjusting the concentration of the cell suspension and by the sample flow rate.

Animals↗
PubMed1991

Carbohydrates in the functions of natural killer cells.

There is little doubt that carbohydrates are crucial to the functions of NK cells. Exogenous carbohydrates alter the cytolytic capabilities of these cells, treatment of NK cells with glycosidases or inhibitors of glycosylation affect function, NK cells can bind selective sugars, and NK cells can be identified and subdivided into functionally distinct subsets on the basis of cell surface carbohydrates. Yet, despite the large number of observations which have been made concerning carbohydrates and NK cells, there is little consensus regarding these studies and few investigations which satisfactorily demonstrate specific mechanisms for the observed effect of the carbohydrates. Almost certainly, the number of diverse observations implies roles for carbohydrates in multiple areas of NK function, probably including target recognition, tissue distribution and post-binding events in the lytic cascade. Hopefully, these observations made to date will be viewed as exciting preliminary studies which will entice more sophisticated investigations designed to elucidate the precise roles of carbohydrates in the functions of NK cells.

Animals↗
PubMed1990

NKR-P1, a signal transduction molecule on natural killer cells.

Natural killer (NK) cells are a subpopulation of large granular lymphocytes characterized by densely staining azurophilic granules. NK cells are able to recognize and lyse various virally infected or neoplastic target cells without previous sensitization or major histocompatibility complex restriction. A 60-kD disulfide-linked dimer, highly expressed on NK cells, was found capable of mediating transmembrane signaling. The gene encoding this signal transduction molecule was cloned and its nucleotide sequence determined. The encoded protein showed significant homology with a number of lectin-related membrane proteins that share receptor characteristics. This protein may function as a receptor able to selectively trigger NK cell activity.

Amino Acid Sequence↗
PubMed1990

Alterations in cell-surface carbohydrates of rat large granular lymphocytes associated with interleukin-2 activation.

The activation of large granular lymphocytes (LGLs)/natural killer (NK) cells with interleukin-2 (IL-2) has been shown to increase the ability of these cells to lyse NK-resistant tumor target cells. Activated LGLs, termed LAK (lymphokine-activated killer) cells, have been demonstrated to be of therapeutic value in vivo against metastatic tumors. The mechanism by which IL-2 induces broadened cytolytic capability, as well as the molecular basis of target recognition and killing by the activated cells has not yet been elucidated. Since carbohydrate moieties have been demonstrated to be of possible significance in the cytolytic cascade of a variety of effector cells, the current study was undertaken to determine if the activation of LGLs with IL-2 is accompanied by an alteration of cell-surface carbohydrates. Two-color flow cytometry was performed to identify LGL/NK cells in populations of nylon wool-nonadherent splenic mononuclear cells and to assess the binding of various lectins to activated as well as nonactivated LGLs. Increases were observed in the binding of four lectins to LGLs after IL-2 activation; Triticum vulgaris (wheat germ agglutinin), Phytolacca americana (pokeweed mitogen), Lycopersicon esculentum (tomato lectin), and Griffonia simplicifolia I-B4 (GSI-B4). The wheat germ, pokeweed, and tomato lectins recognize complex carbohydrates structure consisting of GlcNAc(Bl,4GlcNAc)n while GSI-B4 recognizes alpha-D-galactose terminal end groups. Lectin binding to the activated LGLs was homogenous (i.e., flow cytometry revealed only a single population of fluorescent cells). Lectin binding to LGLs prior to activation was more heterogeneous, however, the tomato lectin uniquely revealed a bimodal distribution of receptors. These data indicate that LGL/NK cells from the rat are heterogeneous in their ability to bind specific lectins, and that IL-2 activation of these cells results in altered expression of specific cell-surface carbohydrates.

Animals↗
PubMed1990

Alpha-mannosidase treatment of NK cells does not inhibit NK cell lytic function.

Alpha-mannosidase was tested for its ability to inhibit lytic activity of nonadherent, mononuclear peripheral blood leukocytes (PBL) against K-562 target cells. Pretreatment of effector cells (60 min., 37 degrees C, pH 7.3) with this enzyme, prior to and after exhaustive dialysis, was examined. Nondialyzed enzyme preparations completely inhibited NK lytic function at all concentrations tested (1.0, 0.5, and 0.25 units/ml). On the other hand, dialyzed enzyme preparations had no inhibitory effect on NK lytic function over the same range of concentrations. The inhibitory effects of the nondialyzed enzyme were due to the presence of (NH4)2SO4, which could be removed by dialysis. Studies were also performed to determine whether enzyme treatment of effector cells resulted in hexose release from cell surface structures. Treatment of effector cells with alpha-mannosidase (dialyzed preparation) resulted in a dose dependent release of mannose. These data demonstrate that NK cell lytic function is not inhibited by pretreatment of effector cells with alpha-mannosidase even though mannose is quantitatively released from cell surface oligosaccharide structures. These results suggest that NK lytic function does not involve an effector cell surface structure bearing terminal alpha-linked mannose residues as previously reported.

Ammonium Sulfate↗
PubMed1990

Isolation and characterization of a cDNA that encodes the core protein of the cytolytic granule proteoglycan in rat natural killer cells.

In this report, we describe the transcription of messenger ribonucleic acid (mRNA) specific for the core protein of chondroitin sulfate proteoglycan (CSPG), the entire sequence of the message for CSPG core protein and the presence of CSPG in the granules of a highly purified population of recombinant interleukin-2 (rIL-2)-stimulated rat natural killer (NK), i.e. adherent lymphokine-activated Killer (A-LAK), cells. The presence of CSPG in A-LAK cell granules was demonstrated by a variety of biochemical and immunologic methods. Further, we have demonstrated the presence of a 1.1-kilobase (kb) transcript for the core protein of CSPG by Northern blot analysis using a specific probe (pPG6) derived from a rat yolk sac tumor cell line (L-2). Three cell types that contained CSPG in granules produced a transcript of 1.1 kb, whereas L-2 cells, which localize CSPG on the cell surface, produced a transcript of 1.3 kb. A complementary DNA (cDNA) library was prepared from rat A-LAK cells and the gene for the CSPG core protein was cloned. From approximately 1.2 X 10(5) recombinant phages, 5 positive clones were obtained. The longest clone, PG-NK-5, was sequenced in its entirety and it was found to encode the entire sequence of the CSPG core protein. The other 4 clones were partially sequenced and were identical to PG-NK-5. Comparison of the sequence of PG-NK-5 with pPG6 indicated that they were nearly identical. However, all NK-cell-derived cDNAs contained a poly(A) tail that started 20 basepairs upstream from other published sequences for CSPG core proteins. These data represent the first description of the sequence of the core protein of CSPG contained in NK cells.

Aggrecans↗
PubMed1989

Monoclonal antibody to a triggering structure expressed on rat natural killer cells and adherent lymphokine-activated killer cells.

To study the cellular structures involved in NK and lymphokine-activated killer (LAK) cell function, we have produced a panel of mAbs that modulate the cytolytic function of a population of cells with LAK activity that derive from large granular lymphocyte (LGL)/NK cells (adherent LAK [A-LAK] cells). In this report, we describe an mAb (3.2.3; IgG1k) that recognizes a triggering structure that is expressed on rat LGL/NK cells and A-LAK cells. This epitope is also expressed on polymorphonuclear leukocytes (PMN). The expression of the epitope identified by mAb 3.2.3 increased progressively on A-LAK cells after culture in the presence of rIL-2. mAb 3.2.3 enhanced the cytolytic activity of NK and A-LAK cells against FcR+ target cells, but not FcR- target cells. However, this effect was not induced by F(ab')2 fragments of 3.2.3. This antibody also induced the release of N-alpha-benzyloxycarbonyl-L-lysine thiobenzy esteresterase by A-LAK cells. These data suggest that the epitope identified by mAb 3.2.3 is on a triggering structure expressed on rat NK cells and A-LAK cells. The expression of the epitope recognized by mAb 3.2.3 on LGL/NK cells and PMN suggests that this structure may be analogous to that identified by the anti-CD16 (-FcR) mAbs. However, the molecule immunoprecipitated by mAb 3.2.3 was a 60-kD dimer composed of two 30-kD chains. These data suggest that mAb 3.2.3 recognizes a unique triggering structure. As mAb 3.2.3 is the first antibody recognizing a determinant with functional significance, selectively expressed on both rat NK cells and A-LAK cells, it will be a useful tool for the study of NK cell ontogeny and function, and the development of cells with LAK activity from the NK cell compartment.

Animals↗
PubMed1988

Natural killer cell infection and inactivation in vitro by the human immunodeficiency virus.

Cytolytic activity of human mononuclear peripheral blood leukocytes from healthy donors, cultured in interleukin-2 conditioned medium, was abrogated by in vitro infection with the lymphadenopathy associated virus (LAV) isolate of the human immunodeficiency virus (HIV). Although viral antigens are not expressed in cultured cells until 14 days postinfection, cytolytic activity was lost as early as 3 days after infection. Loss of cytolytic function was not a result of the release of suppressive factors from either infected cells or uninfected CEM cells since supernatants from neither infected cultures nor CEM cell cultures had any inhibitory effects on the function of uninfected cells. Cultured lymphocytes expressing Leu 11b were also shown to express HIV antigens via immunofluorescence after 14 days in culture. These results suggest that natural killer (NK) cells, as defined by expression of Leu 11b, were infected by HIV in vitro and the loss of lytic function was likely a direct consequence of that infection.

Acquired Immunodeficiency Syndrome↗
PubMed1986

The effects of hexose 6-O-sulfate esters on human natural killer cell lytic function.

Natural cell-mediated cytotoxicity (NCMC) is inhibited by some neutral hexoses and hexose phosphates at 25 to 100 mM concentrations. In this study we describe the effects of hexose 6-O-sulfate esters on NCMC against K-562 target cells. Mannose 6-sulfate, galactose 6-sulfate, N-acetylglucosamine 6-sulfate, and N-acetylgalactosamine 6-sulfate inhibit NCMC in a dose-dependent manner at concentrations of 10 mM and below. Inhibitory effects of mannose 6-sulfate and galactose 6-sulfate were evident at concentrations as low as 1.25 mM. The neutral forms of these sugars, glucose and glucose 6-sulfate, did not inhibit NCMC over this range of concentrations. Comparison of the inhibitory effects of sulfated and phosphorylated forms of mannose and galactose indicated that the sulfated forms are much more potent inhibitors. Formation of effector cell:target cell conjugates was unaffected by the presence of sugar sulfates. Calcium pulse experiments demonstrated that inhibitory effects of sugar sulfates were exerted after the Ca++-dependent triggering step in the NK lytic process. Kinetic studies showed that addition of sugars as long as 60 min after initiation of cultures yielded potent inhibitory effects. Sugar sulfates were not toxic for effector cell populations and effectors were not refractory for lytic function after removal of sugars. Sugar sulfates were inhibitory against multiple tumor types in both human and murine NK lytic assays. These results suggest that the sugar sulfates inhibit NK cells at a postconjugation, posttriggering step involving lectin-like receptors or lectin-like molecules.

Acetylglucosamine↗
PubMed1985

Isolation of bovine eosinophils by density gradient centrifugation.

A method for the isolation of an enriched population (greater than 60%) of bovine eosinophils was developed, using density gradient centrifugation. Eosinophils were isolated from peripheral blood by centrifugation on a density gradient medium of sp gr 1.092. Viability was greater than or equal to 95%, and the isolated eosinophils were found to be functional in chemokinetic and antibody-dependent cellular-cytotoxicity assays. This method represents a simple, rapid method for obtaining bovine eosinophils that can be used in a variety of assays of eosinophil function.

Animals↗