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Biomedical subjects

A Schimpl

Publications and source records attributed to A Schimpl.

At least 73 records · Page 4Linked to original sources
PubMed1982

Expression of endogenous retroviral glycoprotein 70 by antigen-activated cytotoxic and suppressor T lymphocytes of nice.

Concanavalin A-stimulated murine spleen cells and antigen-stimulated B lymphocytes of normal mice express an antigen that reacts with goat antiserum against glycoprotein (gp) 70. Structural analysis of this antigen characterizes it as endogenous viral gp70 that is most likely of xenotropic origin. Activated nonspecific T suppressor cells and cytotoxic T lymphocytes express endogenous viral gp70, whereas nonactivated mouse T or B lymphocytes do not. The presence of endogenous retroviral gp70 is thus a novel marker for activated mouse lymphocytes in general.

Animals↗
PubMed1980

Stimulation of murine B cells with anti-Ig antibodies: dominance of a negative signal mediated by the Fc receptor.

While soluble intact rabbit anti-mouse kappa chain antibodies (RaMK) fail to stimulate [3H] thymidine incorporation in B cells of young mice, the F(ab')2 fragments thereof are stimulatory. This stimulation can be abrogated by the addition of soluble intact RaMK, pointing at the dominance of a negative signal mediated by intact antibodies, probably via their Fc portion. Blocking the interaction between intact antibody, and the Fc receptor of B cells by staphylococcal protein A renders the intact antibodies also stimulatory. Protein A itself is not mitogenic in this system nor does its addition influence B cell activation induced by rabbit F (ab')2 anti-mouse kappa chain antibodies. The data indicate that the Ig receptor of murine B cells can serve as a triggering receptor provided the negative signal mediated by cross-linkage involving the B cells' Fc receptor is avoided.

Animals↗
PubMed1980

Chemical characterization of macrophage cytotoxicity factor, macrophage migration inhibitory factor, T-helper cell-replacing factor and colony-stimulating factor from culture supernatants of concanavalin A-stimulated murine spleen cells.

Supernatants from Concanavalin A-stimulated murine spleen cells were subjected to hydrophobic interaction chromatography on phenyl-Sepharose. Macrophage cytotoxicity factor (MCF), macrophage migration inhibitory factor (MIF), T-helper cell-replacing factor (TRF) and colony-stimulating factor (CSF) were bound at high ionic strength and were released stepwise at low ionic strength. CSF thus could be separated from MCF, MIF and TRF and the bulk of other proteins. Chromatograhy of pools containing MCF, MIF and TRF on Sephadex did not lead to a separation of the three activities which were all found in a molecular weight range of 25.000-55.000. Isoelectric focusing of these pools in pH range from 4 to 9 gave two peaks for MCF in a single sharp peak at pH 5.3. The results demonstrate that the four biological activities can be distinguished on a chemical basis and are accessible for purification and chemical characterization.

Animals↗
PubMed1979

[Soluble mediators as a means of communication between lymphozytes in immune reactions (author's transl)].

Soluble mediators play an important role in the positive and negative regulation of immune reactions. This has been particularly well documented for T-B-cooperation in the humoral immune response to T-dependent antigens. T-helper cells produce a T-cell replacing Factor (TRF) upon mitogenic or antigenic stimulation. It provides the signal to antigen triggered B-cells to begin with active antibody synthesis and secretion and thus it is a positively regulating mediator. Additional functional and some structural characteristics of TRF are described. Antigen specific and non-specific suppressor factors seem to be involved in the negative regulation of immune responses. Thus, the communication between cells of the immune system is largely conducted via soluble signal substances.

Antibody Formation↗
PubMed1979

Studies on the generation and expression of H-2-controlled T helper function in chimeric mice: evidence for two levels of H-2 resitriction.

F1 leads to parental, semisyngeneic/semiallogeneic and fully allogeneic bone marrow radiation chimeras were used as a source of helper T cells in the in vitro anamnestic response to dinitrophenylated keyhole limpet hemocyanin. In F1 leads to parental and in semisyngeneic/semiallogeneic chimeras, a small population of helper T cells restricted to the H-2 haplotype present in the donor only was shown to co-exist with T cells restricted to the shared haplotype. Only the population restricted to the donor H-2 could be demonstrated in allochimeras, presumably due to a lack of antigen-presenting cells of host origin during priming. Under assay conditions where, in addition to T cell/macrophage interactions, a direct T-B cell contact was necessary ("linked" cooperation), the H-2 restrictions observed were absolute. When direct T-B cell contact was made unnecessary by a special experimental protocol ("unlinked" cooperation), H-2 restriction between T and B cells was overcome. Thus, the cellular interactions during the anamnestic immune response to T-dependent antigens seem to be H-2-restricted at two levels: T cell/macrophage and T-B cell interactions.

Animals↗
PubMed1979

Purification and characterization of a mitogenic lectin and a lectin-binding protein from Vicia sativa.

From the seeds of Vicia sativa, a novel mitogenic lectin was isolated. Purification was carried out by affinity chromatography on Sephadex G-100. The tetrameric lectin is a glycoprotein with a molecular weight of Mr 40 000; it consists of two large beta-subunits (Mr 14 000) and two small alpha-subunits (Mr 6000). The N-terminal sequence of both subunits and their amino acid compositions were determined. The lectin agglutinates human erythrocytes, preferring group B, and erythrocytes from rabbits and horses; no agglutination takes place with sheep erythrocytes. Agglutination is inhibited by mono-, di- and tri-saccharides with the configuration of glucose at the free 4-hydroxyl group. The lectin stimulates mitosis in lymphocytes of mice. From the seeds of the same plant, a protein was isolated which binds to the lectin described above. The lectin binder consists of subunits with a molecular weight of 53 500.

Amino Acid Sequence↗
PubMed1977

Mechanism of T-cell help in the immune response to soluble protein antigens. I. Evidence for in situ generation and action of T-cell-replacing factor during the anamnestic response to dinitrophenyl keyhole limpet hemocyanin in vitro.

The involvement of a nonantigen-specific T-helper factor in the anamnestic immune response to dinitrophenyl keyhole limpet hemocyanin is demonstrated employing cultures of unseparated spleen cell populations. In such cultures of primed and boosted spleen cells, a good IgG anti-DNP response could be obtained if the hapten was presented on a heterologous carrier, provided that the homologous carrier was added simultaneously. T-cell depletion and reconstitution experiments show that such a factor, presumably identical with T-cell-replacing factor is produced by primed helper cells upon rechallenge and helps primed B cells, stimulated by soluble heterologous carrier hapten conjugates, to become IgG-secreting cells.

Animals↗
PubMed1977

Mechanism of T-cell help in the immune response to soluble protein antigens II. Reconstitution of primary and secondary in vitro immune responses to dinitrophenyl-carrier conjugates by T-cell-replacing factor.

Spleen cells of dinitrophenyl keyhole limpet hemocyanin (DNPKLH) primed and boosted mice produced a nonantigen-specific helper factor upon in vitro challenge with DNPKLH. This helper factor displays all of the biological characteristics so far described for TRF produced by allogeneic or Concanavalin A stimulation of mouse spleen cells. It restores the primary anti-SRBC response in nude spleen cultures following the same kinetics of action as T-cell-replacing factor (TRF). Conversely, TRF restores the primary in vitro immune response of nude spleen cultures to DNPKLH. TRF also restores the secondary anti-hapten IgG response of T-cell-deprived spleen cell cultures derived from DNPKLH primed and boosted mice. Here the need for carrier specificity is fully overcome. The data therefore suggest that TRF, as a nonantigen-specific maturation signal, is involved in the primary and secondary immune responses to both particulate and soluble antigens.

Animals↗
PubMed1974

Autoradiographic studies on the proliferation of antibody-producing cells in vitro.

A rapid and reliable autoradiographic technique for plaque-forming cells (PFCs) using (14)C rather than tritiated thymidine is described. Its application to PFCs developing in vitro shows that (a) practically all PFCs derive from precursors dividing steadily during the culture period, (b) PFC precursors divide in the absence of T-cell helper function, and (c) at least some PFCs may continue to divide.

Animals↗