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Biomedical subjects

M Nabholz

Publications and source records attributed to M Nabholz.

89 records · Page 5Linked to original sources
PubMed1975

Tolerance to histocompatibility determinants in tetraparental bone marrow chimeras.

Tetraparental bone marrow chimeras were produced by injecting lethally X-irradiated F1 hybrids with relatively high numbers of T-cell-depleted bone marrow cells from both allogeneic parental strains. The mice survival in excellent health and showed a stable, approximately 50:50 (parent:parent), lymphoid cell chimerism lasting for at least 7 mo after irradiation; regeneration of host-type hemopoietic cells was very limited. Thymus, lymph node, and thoracic duct lymphocytes showed specific unresponsiveness to host mixed leukocyte reaction (MLR) determinants. Similarly specific tolerance to H-2 antigens of host type was demonstrated in spleen and lymph node. No suppressor cells could be demonstrated in either system and blocking serum factors could not be found. The results suggest specific deletion of functional T cells reactive to host-type MLR and cell-mediated lympholysis determinants.

Animals↗
PubMed1975

I-region-associated determinants: expression on mitogen-stimulated lymphocytes and detection by cytotoxic T cells.

We have studied the expression of Ia-antigens, controlled by genes in the I-region of the H-2 complex, on phytohemagglutinin (PHA)-stimulated lymph node cells and on lipopolysaccharide (LPS)-stimulated spleen cells, and have compared these two types of cell populations as targets for killer cells in the cell mediated lympholysis (CML) assay. PHA targets are almost completely insensitive to complement-mediated lysis by anti-Ia sera while the majority of LPS targets are killed. T cell-mediated lysis against I-region determinants was also detected, and these determinants, in contrast to H-2K and H-2D CML determinants, seem to be much more strongly expressed on LPS-stimulated cells. No differences in the kinetics of the response to K- or I-region CML determinants were observed. Lysis by killer cells can also be obtained against incompatibilities which do not give rise to strong skin graft rejection and against determinants which are most probably controlled by genes outside the K-D interval.

Animals↗
PubMed1975

Human intraspecific somatic cell hybrids: a genetic and karyotypic analysis of crosses between lymphocytes and D98/AH-2.

A number of human intraspecific hybrids were produced by fusing the 8-azaguanine-resistant cell line D98/AH-2 with PHA-stimulated lymphocytes from a normal human male, followed by selection in HAT medium. The parent cells differed in zymogram patterns for 4 enzyme systems. Hypoxanthine-guanine phophoribosyltransferase was missing in D98/AH-2 and was determined in the hybrids by the normal gene derived from the lymphocyte donor's X chromosome. The HL-A antigens of the lymphocyte donor as well as the W28 specificity from HeLa were easily recognized by a cytotoxicity assay on the hybrid cells, while D98/AH-2 itself was not killed in the normal way by any HL-4 typing sera. The initial hybrid karyotype in all lines was relatively stable, but slow loss of chromosomes occurred following extended growth in culture. The importance of the culture conditions for the rate of chromosome loss was demonstrated. The behavior of several chromosomes was followed in the hybrids and their derivatives. There was relatively nonspecific loss of small numbers of chromosomes, showing that loss of chromosomes from both the D98/AH-2 and the normal lymphocyte parent can occur. Cell lines resistant to 6-thioguanine were selected from the sensitive hybrids. Most had lost the lymphocyte donor's X chromosome, thereby losing the only active allele for HGPRT present in the initial hybrids. However, one line, DMR41, apparently retained the X chromosome and may have a mutated allele for HGPRT. Two lines that are the products of spontaneous segregation are also described. DM4CS and DM17A.

Acid Phosphatase↗
PubMed1975

Further miniaturization and automation of in vitro lymphocyte cultures.

A microtechnique (10 mul culture volume) for in vitro lymphocyte cultures is described, which, compared with current miniaturized techniques, permits a four to 20-fold reduction of both medium volume and cell numbers. Furthermore, two alternative procedures for harvesting and washing radioisotope labelled cells are described. The first, making use of a conventional harvesting device, collects cells on glass fibre filters in a two to three-fold shorter time than that needed for the current semi-automatic collectors. The second takes advantage of the possibility of washing and fixing the cells in their culture wells and allows processing of more cultures with fewer manual operations. Various technical aspects of the micro-culture system are described and discussed with special reference to automation problems.

Animals↗
PubMedDate not supplied

Expression of interleukin-2 receptors as a differentiation marker on intrathymic stem cells.

The thymus is regarded as the primary site for T-cell lymphopoiesis, but very little is known about the lineage inter-relationships of cells within that organ. At least four subpopulations of mouse thymocytes can be defined on the basis of staining with monoclonal antibodies directed against the T-cell differentiation antigens Lyt-2 and L3T4 (ref. 2). Thus immunocompetent (medullary) thymocytes, like peripheral T cells, express either Lyt-2 (cytotoxic phenotype) or L3T4 (helper phenotype) but not both, whereas non-functional (cortical) thymocytes express both markers. In addition, a small subpopulation comprising 2-3% of cells in the thymus and expressing neither Lyt-2 nor L3T4 has recently been described. The latter cells have the properties of intrathymic 'stem cells' in that they are the first to appear in the embryonic thymus and at least some can be shown to give rise, both in vivo (ref. 4. and our unpublished data) and in vitro, to other thymocyte subpopulations. We show here that 50% of Lyt-2-/L3T4- cells in the adult thymus express receptors for the polypeptide growth hormone interleukin-2 (IL-2) whereas other cells in the thymus do not. Furthermore, immunohistochemical localization studies on frozen sections indicate a disperse distribution of IL-2 receptor-positive cells in both the cortex and medulla. These novel findings have potential implications in the context of current models of differentiation pathways within the thymus.

Age Factors↗
PubMedDate not supplied

Similarities between interleukin-2 receptor number and affinity on activated B and T lymphocytes.

Interleukin-2 (IL-2) is a T-cell-derived polypeptide hormone of 133 amino acids which exerts its growth-promoting activity via a surface receptor. Originally, IL-2 was believed to be a unique growth factor for activated T cells; more recent studies, however, have demonstrated that certain B-cell tumours as well as normal activated B lymphocytes express a surface molecule which is recognized by monoclonal antibodies directed against the IL-2 receptor. Furthermore, we and others have shown recently that activated B cells proliferate in response to either immunoaffinity-purified or recombinant IL-2. These controversial findings prompted us to undertake a detailed quantitative comparison of IL-2 receptor expression on activated B and T cells. We show here, using biosynthetically labelled IL-2(3H-IL-2) and anti-IL-2 receptor antibody (3H-PC61) that activated B and T cells express both high-affinity (apparent dissociation constant, Kd approximately 20 pM) and low-affinity (Kd approximately 1,000 pM) IL-2 receptors. Binding of IL-2 to both classes of receptor is inhibited by the monoclonal anti-IL-2 receptor antibody PC61. B blasts express half as many total IL-2 binding sites or PC61 binding sites as T blasts, and the ratio of the number of low- to high-affinity receptors for each cell type is approximately 10:1. Immunoprecipitation analysis of surface-labelled blasts indicates that B and T cells have IL-2 receptors of similar relative molecular mass. Taken together, these data suggest strongly that IL-2 can act as a growth hormone for both B and T lymphocytes.

Animals↗
PubMedDate not supplied

The inducible cytotoxic T-lymphocyte-associated gene transcript CTLA-1 sequence and gene localization to mouse chromosome 14.

Classical phenomenological approaches to the study of the mechanism of T-cell-mediated cytotoxicity have now given way to a search for molecules involved in this function; this is attempted either by subcellular and biochemical fractionation of material from cytotoxic cells, or through the characterization of molecules recognized by cytotoxicity-inhibiting monoclonal antibodies Molecules having a role in cytotoxicity may also be identified by detecting the corresponding messenger RNA transcripts. Such an approach may include, as a first step, the search for transcripts as specific as possible to cytotoxic T cells; only secondarily can their actual relevance to cytotoxicity be investigated. We report here the preparation and systematic screening of a differential complementary DNA bank, in which we detected three distinct messenger RNA transcripts (CTLA-1, CTLA-2 and CTLA-3) present in various cytotoxic T cells but not (or less so) in a range of non-cytotoxic lymphoid cells. We describe the co-inducibility of these transcripts and of cytotoxicity in thymocytes and hybridoma cells, the sequence of CTLA-1 cDNA, its protein homology with serine esterases and the localization of the corresponding gene to mouse chromosome 14.

Amino Acid Sequence↗