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L Mauser

Publications and source records attributed to L Mauser.

10 recordsLinked to original sources
PubMed1990

Growth of murine thymocytes in vitro in chemically defined medium.

Immature T cells proliferate, diversify their repertoire of antigen specificity, are selected for MHC-restricted function, are selected for non-self reactivity and undergo maturation in the thymus. The mechanisms underlying thymic development are poorly understood. One reason for this is that murine thymocytes generally die when cultured in vitro under conditions which normally support lymphocyte growth. We describe conditions under which CD4-CD8- thymocytes proliferate at a high rate and acquire maturation-associated markers in vitro in the absence of exogenous mitogenic stimuli. CD4+CD8- cells also multiplied in the absence of added lymphokines while CD4-CD8+, but not CD4+CD8+, cells proliferated in the presence of exogenous IL-2. Proliferation of CD4-CD8- cells was associated with production of both IL-1 and IL-2. Proliferation of unfractionated, CD4-CD8- and CD4+CD8- thymocytes was dependent upon interaction of IL-2 with its receptor. CD4-CD8- cells acquired CD4 and/or CD8 markers during culture, indicating that, in addition to the proliferation, some maturation occurred. Proliferation occurred in complexes containing one or more central stromal cells. The results are discussed in relation to their possible relevance to thymocyte development.

Animals↗
PubMed1988

Characterization of cells comprising murine thymocyte multicellular complexes.

Characterization of complexes between thymocytes and thymic stromal cells was facilitated in the present study by demonstrating that complexes would reform if cells were incubated for 1.5 to 2 h in vitro at ambient temperature. Several immunologic approaches were used to determine the phenotype of complexed cells. Bound T cells were 97% double-positive (CD4 and CD8), 3% double-negative and greater than 99% CD3 positive by using immunoperoxidase immunohistology on cytospins. Five percent expressed the TCR beta-chain and 1 to 2% were IL-2R positive. The percentages were the same whether complexes were preformed in vivo or formed in vitro. Despite the apparent absence of single positive cells in complexes, when isolated CD4 or CD8 positive cells were tested for their ability to bind to adherent thymic macrophages, each subpopulation contained some cells which were capable of complex formation. When thymocytes were fractionated by density, steroid sensitivity or peanut agglutinin positivity then allowed to form complexes, cells with an immature phenotype had a greater propensity for complex formation. Central stromal cells all were class II MHC gene product (I-A and I-E) positive, expressed macrophage-associated Ag (B23.1 and MAC-1), were negative for cytokeratin but positive for vimentin, were reactive with a polyclonal antimacrophage serum, but did not express dendritic cell Ag (33D1). The data demonstrate that immature thymocytes bind exclusively to class II MHC gene product positive thymic macrophages. This binding step may play a role in the acquisition of T cell function in the thymus.

Animals↗
PubMed1983

Level and temporal pattern of naturally cytolytic cells during acute Graft-versus-Host Disease (GVHD) in the rat.

The purpose of the present study was to determine the level of nonadherent lymphoid cells from Graft-verus-Host Disease (GVHD) rats able to naturally kill (NK/NC cells) various solid tumor or lymphoma cells in vitro. Acute lethal GVHD was produced in either newborn or adult (DA x LEW)F1 rats by iv injection of LEW spleen and lymph node (LN) cells. Controls received the same dose of syngeneic cells. At 7, 14, and 21 days after cell injection, the ability of non-adherent mononuclear cells from the LN, spleen, peripheral blood lymphocytes (PBL), marrow, and thymus to kill 51Cr-labeled dog (DT-5) lymphoma, and undifferentiated sarcoma (11031) or human (HUS-2) sarcoma cells in vitro was determined. Only spleen and marrow of controls caused significant 51Cr release from the target cell lines. However, LN, spleen, marrow, PBL, and thymus from neonates and adults with GVHD of 7 days duration caused greater release from all targets than controls (P less than 0.05-0.001). By Day 14 the level of 51Cr released was significantly less than controls except for the values from LNs and thymus which remained elevated. By Day 21 all lymphoid compartments exhibited a decrease in NK/NC cells. Thus, early during acute GVHD, there is an activation and/or expansion of NK/NC cells while later-stage GVHD rats have depressed NK/NC levels.

Acute Disease↗
PubMed1983

Polypeptide chain initiation in eukaryotes: reversibility of the ternary complex-forming reaction.

In the last step of polypeptide chain initiation in eukaryotes, the interaction of the 40S preinitiation complex eIF-2.GTP.Met-tRNAi.40S [the complex between the 40S ribosomal subunit and the ternary complex containing equimolar amounts of eukaryotic initiation factor 2 (eIF-2), GTP, and eukaryotic initiator methionyl tRNA (Met-tRNAi)] with a 60S ribosomal subunit in the presence of mRNA, cap binding protein (with "capped" messengers), ATP, and the initiation factors eIF-3, eIF-4a, -4b, -4c, and eIF-5, results in the formation of an 80S initiation complex (Met-tRNAi.80S.mRNA) with concomitant hydrolysis of GTP and liberation of eIF-2 for recycling in subsequent initiation events. However, at physiological Mg2+ concentrations, GDP is known to have approximately equal to 100-fold greater affinity than GTP for eIF-2 and eIF-2 is believed to be released in the form of an eIF-2.GDP complex. Previously, we have shown that initiation factor SP (for eIF-2-stimulating protein) promotes the exchange of eIF-2-bound GDP for GTP and catalyzes ternary complex formation in the presence of Met-tRNAi. Binding of GDP by eIF-2 is indeed so tight that, as we now show, homogeneous preparations of eIF-2 contain upward of 0.5 mol of GDP/mol of eIF-2. We further show that, in the presence of Mg2+ and catalytic amounts of SP, ternary complex formation conforms to the overall reversible reaction eIF-2.GDP + GTP + Met-tRNAi in equilibrium eIF-2.GTP.Met-tRNAi + GDP.

Eukaryotic Initiation Factor-2↗
PubMed1982

Initiation of protein synthesis in eukaryotes. Nature of ternary complex dissociation factor.

Excessive concentrations of the eukaryotic initiation factor 2(eIF-2).stimulating protein, a factor that catalyzes the formation of binary (GTP.eIF-2) and ternary (GTP.eIF-2.initiator methionyl-tRNA) initiation complexes at physiological Mg2+ concentrations, can cause ternary complex dissociation when the Mg2+ concentration is raised from 0.5 to 5.0 mM. Stimulation of ternary complex formation and dissociation have similar (a) pH optima, (b) metal ion specificity, and (c) sensitivity to phosphorylation of the eIF-2 alpha subunit. The results suggest that ternary complex dissociation is an artifact with no physiological significance.

Animals↗
PubMed1982

Mechanism of polypeptide chain initiation in eukaryotes and its control by phosphorylation of the alpha subunit of initiation factor 2.

Earlier, we isolated eukaryotic initiation factor 2 (eIF-2)-stimulating protein (SP) as a homogeneous complex with eIF-2 (eIF-2-SP) and showed that, in the presence of Mg2+, eIF-2-SP promotes formation of a ternary complex with GTP and eukaryotic initiator methionyl tRNA (Met-tRNAi) (eIF-2-GTP-Met-tRNAi) catalytically. We now show that SP-bound eIF-2 exchanges with eIF-2 (eIF-2 exchange). Furthermore, in the presence of Mg2+, eIF-2-SP catalyzes the exchange of eIF-2-bound [3H]GDP with unlabeled GDP or GTP (GDP exchange) and the release of [3H]GDP when the ternary complex is formed from eIF-2-[3H]GDP, GTP, and [35S]Met-tRNAi. All these reactions are blocked by alpha-subunit, but not by beta-subunit, phosphorylation of eIF-2. The eIF-2 and GDP exchanges are compatible with the reaction eIF-2-GDP + SP in equilibrium EIF-2-SP + GDP reminiscent of the exchange between the Tu and Ts components of prokaryotic elongation factor 1 (EF-Tu and EF-Ts, respectively) EF-Tu-GDP + EF-Ts in equilibrium EF-Tu-EF-Ts + GDP. Due to the high affinity of GDP (approximately 100 times greater than that of GDP) for eIF-2, 40S (eIF-2-GTP-Met-tRNAi-40S) to 80S (Met-tRNAi-mRNA-80S) initiation complex conversion, which is accompanied by GTP hydrolysis, probably releases eIF-2 as eIF-2-GDP. Our results suggest that, in the presence of Mg2+, GDP binding restricts the availability of eIF-2 for chain initiation and that SP relieves this restriction in a catalytic fashion, provided that the alpha subunit of eIF-2 is not phosphorylated.

Animals↗
PubMed1981

A rapid technique for detecting IgGFc and complement receptors on T and B cells in the neonatally thymectomized and normal adult rat.

Numerous studies have demonstrated the presence of IgGFc and C3 receptors on mammalian lymphoid cells. However, the further characterization of these cells as T, B, or null has been cumbersome and time consuming. A simple method is described for surface fluorescent labeling of (DA X L)F1 rat cell suspensions indirectly with either anti-rat IgM (sIg+) or monoclonal anti-rat thymocyte (sT+) antibody and then rosetting with EA or EAC. Staphylococcus protein A had no significant effect on the level of sIg+ or sT+ attained. From 58-78% of IgGFc+ cells were SIg+ with 14-18% sT+ in the spleen, lymph nodes, and peripheral blood. Almost 100% of C3+ cells were sIg+. Neonatally thymectomized adults exhibited a 254-413% decrease in sT+ cells but a 154-329% increase in sIg+ and a 177-330% increase in null cells. They also exhibited a 140-400% increase in IgGFc+ and C3+ cells in all lymphoid compartments. Fifty-two to 65% of IgGFc+ cells and again almost 100% of C3+ were sIG+. The methods and results are discussed as a basis for studies of B and T lymphocyte maturation and function within various rat lymphoid compartments.

Animals↗
PubMed1975

Immunologic properties of mast cells from rats infected with Nippostrongylus brasiliensis.

The concentration of IgE in the serum of Sprague-Dawley rats increased after infection with Nippostrongylus brasiliensis (NB). The IgE concentration in normal rats was less than 1 mug/ml. After re-infection with NB, the concentration increased in 100 to 300 mug/ml. Mast cells were purified from peritoneal cells of both normal and NB-infected animals. Purified mast cells from the infected animals released histamine upon exposure to NB antigen. The antibody specific for IgE released histamine from purified mast cells of both normal and infected animals. Dose-reponse curves of histamine release suggested that mast cells from NB-infected animals bear more IgE molecules than normal mast cells. Binding of 125I-labeled rat E myeloma protein with normal mast cells was demonstrated by autoradiography. Under the same experimental conditions, mast cells of infected animals were not labeled with 125I-IgE. Mast cells from both normal and infected animals failed to combine 125I-labeled IgG. The number of IgE molecules bound per mast cell was determined by incubating 125I-labeled IgE with purified mast cells. When mast cells were incubated incubated in 0.6 to 2 mug/ml of IgE, the number of IgE molecules combined with the mast cells from infected animals was about 10% of that bound with normal mast cells. The results indicated that a large proportion of IgE receptors on mast cells of infected animals was occupied by their own IgE. No significant difference was observed between normal mast cells and those of infected animals with respect to histamine content and intracellular levels of cyclic nucleotides.

Ancylostomatoidea↗