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G F Fischer

Publications and source records attributed to G F Fischer.

44 records · Page 3Linked to original sources
PubMed1991

Elucidation of apparent non-maternity with DNA probes detecting highly polymorphic single locus systems.

During paternity testing, we encountered the following constellation in the Jk system: the mother's phenotype was Jk(a-b+), while the son was typed as Jk(a+b-). The deduced genotype of the mother would have been Jkb Jkb, and each offspring should then express the Jk(b) antigen. Consequently, non-maternity would be deduced. Since no material was available for extended family studies or HLA typing, except for the DNA of the propositi, only RFLP analysis could bring clarification in this case. The application of four highly polymorphic single locus probes proved the maternity and hence the existence of a Jk-Null allele. We conclude that direct testing at the DNA level may help resolving cases where, by conventional parentage testing, conclusive results are unachievable because of putative 'Null' alleles.

Alleles↗
PubMed1991

[The use of highly polymorphic DNA systems in the demonstration of mixed chimerism following bone marrow transplantation].

The demonstration of restriction fragment length polymorphism (RFLP) of the highly polymorphic systems MS1, MS31, g3, and MS43 to detect mixed chimerism after bone marrow transplantation is discussed. Degree of heterozygosity, somatic stability and sensitivity are the parameters investigated to demonstrate the practicability of this method. Examples of mixed chimerism after bone marrow transplantation are shown.

Bone Marrow Transplantation↗
PubMed1991

[Identification of an old frozen alcohol blood sample using a genetic probe technique].

Determination of ethanol concentration in a blood sample drawn from a person who caused a serious car crash showed a level which was markedly above the upper limit tolerated legally i.e. 0.08%. At the court hearing the accused car driver challenged the drunken driving charge and claimed that there might have been a mix up of the blood samples, whereby his was replaced by another blood sample, since the tube containing his blood was not marked with his name. The blood sample had been stored without anticoagulants for about 6 months at -20 degrees C. Due to haemolysis it was impossible to determine conventional haemogenetic marker systems. We therefore tried to extract DNA from the blood sample and to determine the restriction fragment length polymorphism (RFLP) by means of five DNA probes recognizing highly polymorphic single-locus systems as described by Jeffreys et al. We analyzed the RFLP's of both the old blood sample and of fresh blood drawn from the accused car driver and we were able to identify the blood sample as certainly having been taken from the accused.

DNA↗
PubMed1990

Signal transduction in lymphocytic and myeloid cells via CD24, a new member of phosphoinositol-anchored membrane molecules.

The CD24 Ag is present on human B cells from the earliest stages of B lineage development and is lost on terminal B cell maturation to plasma cells. This Ag is also expressed on mature forms of granulocytes. We studied the effects of CD24 mAb on the function of both lymphocytic and myeloid cell types. We found a clear-cut increase in free cytoplasmic calcium when tonsil B cells or mononuclear cells from B cell chronic lymphatic leukemia patients were preincubated with CD24 mAb and further stimulated with goat F(ab')2 anti-mouse Ig antibodies. The same experimental setting with granulocytes instead of B lymphocytes led to the triggering of hydrogen peroxide production in these cells. CD24 Ag is expressed at higher levels on activated granulocytes and is anchored to the plasma membrane by a phosphoinositol linkage. In conclusion we provide evidence that the CD24 Ag are functional molecules in cells of different lineage, playing a signal transducing role in cell function.

Antibodies, Monoclonal↗
PubMed1990

CD27 expression by a distinct subpopulation of human B lymphocytes.

CD27 is present on the surface of a major subset of peripheral blood T lymphocytes. In this report we show that CD27 is also expressed on a subpopulation of the normal human B cell lineage which is absent from cord blood but present in tonsils and in the peripheral blood of adult individuals. CD27+ B lymphocytes are characterized by the following criteria: (a) in terms of physical properties, the CD27+ B cells form a population with an increased cell size combined with a decreased cell density; (b) the CD27 expression of tonsillar B lymphocytes is postively correlated with mIgA but negatively correlated with membrane IgM/membrane IgD positivity; (c) CD27 on B cells can be induced selectively by the combination of Staphylococcus aureus plus interleukin 2, but not by either treatment alone, and (d) CD27+ B lymphocytes express high levels of the adhesion structures LFA-1 (CD11a), ICAM-1 (CD54), LFA-3 (CD58) and of the lymphocyte homing receptor CD44. These latter findings suggest that CD27+ B cells are predispose to form cell-cell interactions. Accordingly, within 3 h of cell culture CD27+, but not CD27-, B lymphocytes were found to form LFA-1-mediated homotypic B cell clusters.

Antibodies, Monoclonal↗
PubMed1988

T cell stimulation via CD2 molecules is regularly accompanied by an increase in cytoplasmic pH. Different effects of lectins and CD3 antibodies.

The stimulation of different cell types with growth factors is often accompanied by a rapid intracellular alkalinization. By using mitogenic lectins, cluster of differentiation (CD)2 and CD3 mAb, as stimuli, we studied early changes of the intracellular pH in the activation process of resting human PBL. We found increases in free cytoplasmic Ca2+ levels and DNA synthesis but no intracellular alkalinization in the early activation phase upon stimulation with the mitogenic lectins, Con A, and PHA. Similarly stimulation with CD3 mAb led in most instances to no detectable pH shifts. Only in 7 out of 30 experiments was CD3 mAb-induced alkalinization observed. In contrast, stimulation with mitogenic combinations of anti-CD2 mAb led in all instances to rapid and clear-cut intracellular pH shifts very similar to those observed upon stimulation with PMA. In medium lacking sodium bicarbonate the intracellular alkalinization via the CD2 structure could be blocked by the amiloride analogue 5-(N-methyl-N-isobutyl)amiloride (MIA), which indicates that this increase in pH is mediated by the amiloride-sensitive Na+/H+ antiporter. Blockade of this antiporter had no negative effect, however, on T cell proliferation as measured by thymidine incorporation. In contrast, significantly enhanced proliferation rates were observed after stimulation with mitogenic combinations of anti-CD2 antibodies in the presence of MIA. No such effect of MIA could be observed in lectin induced T cell stimulation. These findings indicate that stimulation of the Na+/H+ antiporter via the CD2 structure is neither a prerequisite for T cell proliferation nor does it promote T cell growth. It rather seems to function in a regulatory role. In its absence, superinduction of proliferation can be achieved.

Amiloride↗
PubMed1986

T cell stimulation via the erythrocyte receptor. Synergism between monoclonal antibodies and phorbol myristate acetate without changes of free cytoplasmic Ca++ levels.

We observed that certain E-receptor antibodies (CD2 antibodies) can induce proliferation of resting human T cells in the presence of PMA, while other CD2 antibodies fail to have such an effect. The same CD2 antibodies that were mitogenic in the presence of PMA (9.6, X11, VIT13), but not the nonreactive ones, were also able to induce T cell proliferation via the so-called alternative pathway of T cell activation, i.e., when added pairwise in certain combinations to T cells in the absence of PMA. While the simultaneous addition of two comitogenic CD2 antibodies (9.6 or X11 plus VIT13) or the addition of a single nonmitogenic CD3 antibody (VIT3) led to a clearcut elevation of intracellular Ca++ levels, no such effect could be observed after the addition of one CD2 antibody alone. Even in the presence of PMA, one comitogenic CD2 antibody alone was unable to trigger a significant Ca++ response, although this combination induced a proliferative response. These data indicate that, distinguishable by their influence on free cytoplasmic Ca++, there are two different mechanisms of T cell activation via CD2. While simultaneous triggering with two antibodies leads to cell proliferation preceded by an increase of Ca++ levels, stimulation with one antibody plus PMA results in proliferation without a measurable early Ca++ response. We conclude that T cells treated by certain CD2 antibodies alone already recognize an activation signal probably unrelated to Ca++ homeostasis, a signal that can further be developed by PMA to result in a completely developed proliferative response.

Antibodies, Monoclonal↗