Search PubMed⌕ Search

Biomedical subjects

T F Schulz

Publications and source records attributed to T F Schulz.

At least 109 records · Page 6Linked to original sources
PubMed1989

HIV and HIV-infected cells differentially activate the human complement system independent of antibody.

The human retroviruses HTLV-I and HIV-I have previously been shown not to be lysed by human serum. An interaction between HIV and the complement system, however, has not been investigated in any detail. In this report we show that purified HIV as well as HIV-infected cells activate the complement system. In the case of virus-infected cells this activation is mediated by the alternative pathway of complement, whereas the classical pathway seems to be in operation for the triggering of the complement system by purified virus and recombinant envelope glycoprotein (gp 160). We demonstrate that this leads to the deposition of C3b and/or C3bi on the surface of infected cells. But the HIV-infected cells are not lysed by human complement. C3 fragments deposited on the surface of HIV-infected cells are capable of mediating immune adherence to complement receptor-bearing cells, such as human erythrocytes and phagocytes. Whether this might have an influence on infectivity of HIV for certain cells bearing complement receptors has yet to be shown.

Cell Line↗
PubMed1989

Recombinant peptides derived from the env-gene of HIV-2 in the serodiagnosis of HIV-2 infections.

We produced recombinant envelope-derived peptides of HIV-2 for use in a diagnostic enzyme-linked immunosorbent assay (ELISA) or Western blot by expressing several restriction enzyme fragments from the env gene of HIV-2 in the bacterial fusion vector pEX-3. On Western blots, 17 out of 18 anti-HIV-2-positive sera available to us reacted strongly with those recombinant peptides which were derived from, or extended into, the transmembrane protein of HIV-2. In contrast, recombinant peptides derived from the external envelope glycoprotein were only weakly recognized by two sera. We observed a cross-reactivity of some human sera containing antibodies to HIV-1 with the HIV-2 peptides derived from the transmembrane protein of HIV-2. In spite of this cross-reactivity, a serological distinction between anti-sera to HIV-1 and HIV-2 can be attempted by simultaneous testing in ELISA on recombinant peptides derived from the transmembrane protein of HIV-1 and HIV-2.

AIDS Serodiagnosis↗
PubMed1989

C3bi-binding protein on Candida albicans: temperature-dependent expression and relationship to human complement receptor type 3.

We investigated in detail the previously described capacity of pseudohyphae of Candida albicans to bind C3-coated particles. We show that the expression of the C3bi receptor of C. albicans was dependent upon the growth temperature of the fungi. C. albicans grown at 30 degrees C bound strongly to EAC1423bi, whereas those cells grown at 38.5 degrees C were completely devoid of this capacity. The molecule responsible for the attachment of EAC1423bi was heat labile and trypsin sensitive. Several, but not all, monoclonal antibodies to the alpha-chain of human complement receptor type 3 (CR3) stained C. albicans, and this reactivity was expressed in parallel with the capacity of C. albicans to bind EAC1423bi, i.e., both were dependent on the growth temperature of the fungi and were trypsin sensitive. In contrast to CR3, the binding of EAC1423bi to C. albicans did not require the presence of divalent cations. Rabbit immunoglobulin G antibodies directed against C. albicans inhibited the binding of EAC1423bi to C. albicans but not to human CR3. These inhibiting IgG antibodies recognized antigens expressed on the surface of pseudohyphae but not those of yeast cells. OKM-1, a monoclonal antibody to human CR3 inhibited the attachment of EAC1423bi to CR3 and also to C. albicans. OKM-1 precipitated a 130-kilodalton band from solubilized 125I-labeled C. albicans. We conclude that the complement receptors on C. albicans and human CR3 were antigenically related but not identical and that they differed in their functional characteristics.

Animals↗
PubMed1989

Inoculation of New World primates with the human immunodeficiency virus.

The susceptibility of common marmosets and cotton-top tamarins to infection by HIV-2 in vivo was tested. One year and 19 months, respectively, post-inoculation, sera taken from three of four animals from each species are reactive for HIV-2 antibodies and HIV-specific nucleotide sequences were demonstrated in short-term cultures of PBL from two cotton-top tamarins. The animals remain in good health.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Expression of leucocyte function-associated antigen-1 and 7F7-antigen, an adhesion molecule related to intercellular adhesion molecule-1 (ICAM-1) in non-Hodgkin lymphomas and leukaemias: possible influence on growth pattern and leukaemic behaviour.

In 160 non-Hodgkin lymphomas (NHL) of B and T cell origin the expression of leucocyte function-associated antigen-1 (LFA-1) and one of its counter-structures named 7F7-antigen was studied. Functional and structural similarities and the 7F7-reactivity of pICAM-1 transfected COS-cells prove that 7F7-antigen is identical with ICAM-1. The expression of both adhesion structures occurred variably and clearly depended on the maturation stage and on the B and T cell origin of lymphomas but was not associated with the proliferative status of tumour cells. The concomitant expression of both adhesion molecules was a characteristic feature of germinal centre derived NHL, particularly of those with neoplastic follicular structures (corr. contingency coeff. = 0.506; P less than 0.02), whereas both adhesion structures were less often expressed on lymphomas with a more diffuse pattern of tumour infiltration. Most B-NHL of low-grade malignancy expressed LFA-1 while their counterparts of high-grade malignancy often tended to be LFA-1 negative. In B cell neoplasias of low-grade malignancy the lack of ICAM-1 and a leukaemic course of the disease were significantly correlated (P less than 0.0005). The results indicate that the differential expression of both adhesion molecules may account for distinct patterns of growth and spread in subtypes of lymphoid malignancies.

Antigens, Differentiation↗
PubMed1989

Effect of D-penicillamine on the expression and propagation of the human immunodeficiency virus by H9 T-lymphoblastoid cells.

The effect of D-penicillamine on the replication of the Human Immunodeficiency Virus (HIV) in H9 T-lymphoblastoid cells was evaluated. HIV-infected and uninfected H9 cells were incubated for a period of 6 weeks with various concentrations of D-penicillamine. During the first 8 days, D-penicillamine (at concentrations of 0-150 micrograms/ml) did not influence growth and viability of H9/H9-IIIB cells. However, long term cultures and higher doses of the drug caused a decay in cell number and viability of the cultured cells. Up to the 8th day of culture, D-penicillamine did not exert an inhibiting effect on the number of HIV-infected cells but did suppress HIV-antigen production by up to 29%. After 6 weeks, in addition to a decrease of the relative viral antigen concentration from 390-500 ng/ml in the medium control to 210-320 ng/ml in cultures containing 150 micrograms D-penicillamine/ml, D-penicillamine also reduced the percentage of HIV-positive cells. Thus our results demonstrate an antiviral effect of D-penicillamine in H9 cultures.

Cells, Cultured↗
PubMed1988

[Etiology--characteristics of HIV infection].

In this study the structures of the AIDS-virus are presented, furthermore the cross-reactivity of HIV-1 and HIV-2 is described as well as the known genes of both viruses. The mechanism of cell infection, its kinetics and the special role of activated T-cells and macrophages in this process are outlined. This interrelation characterized phenomenologically based on the neopterin data available is now supported by experiments at a molecular level. This should lead to therapeutical and diagnostical consequences.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Identification and characterization of a novel membrane activation antigen with wide cellular distribution.

A monoclonal antibody, 7F7, raised against the Raji B lymphoblastoid cell line reacted with about 35% of peripheral blood B cells, germinal center B cells, follicular dendritic cells and some vascular endothelial cells. Although not found on resting T cells this antigen was strongly expressed on CD4+ and CD8+ T cells activated with phytohemagglutinin, pokeweed mitogen and anti-T3, and its expression on B cells was enhanced after stimulation with pokeweed mitogen. It is strongly expressed 24 h after stimulation with phytohemagglutinin and its expression is reduced but not eliminated by cyclosporin A treatment. The molecule defined by antibody 7F7 is found on some, but not all, B cell lines, on an HTLV-I-transformed T cell line and on the promyelocytic cell line U937. Immunoprecipitation from externally and metabolically labeled Raji cells revealed a single-chain molecule of 85 kDa.

Animals↗
PubMed1988

Involvement in the initiation of T cell responses and structural features of an 85-kDa membrane activation antigen.

A monoclonal antibody, 7F7, directed at a recently described membrane activation antigen of 85 kDa was found to inhibit the T cell proliferation induced by an anti-CD3 antibody, phytohemagglutinin A and concanavalin A. The T cell response to allogenic stimulator cells was also weakly inhibited. The inhibition of these T cell responses was only obtained if the antibody was added within the first 8 h (first 24 h in the case of the concanavalin A response) of culture. In addition the antibody inhibited the formation of cellular aggregates seen in stimulated cultures when added within the first 8 h. The membrane glycoprotein recognized by 7F7 is shown to have a slightly different molecular mass on cells of different lineage, a protein core of 55 kDa and to contain 30-50% of N-linked as well as a small amount of O-linked carbohydrates and sialic acid residues. This study suggests that the highly glycosylated membrane activation antigen defined by antibody 7F7 could contribute to the contact between those cells which are involved in the initiation of T cell responses.

Antibodies, Monoclonal↗
PubMed1988

Structural and functional relationships among receptors and regulators of the complement system.

The classical and alternative pathway of complement activation are regulated by a series of fluid phase and cell-bound factors, some of which at the same time serve as receptors for fragments of C3 and C4. These molecules are factor H, CR1 (C3b/C4b receptor), CR2 (C3d/EBV receptor), C4BP (C4b binding protein), DAF (decay accelerating factor), MCP (membrane cofactor protein; earlier designated p45/70), CR3 (iC3b receptor or Mac-1) and CR4 (protein 150/95). Due to structural, genetic and functional features these factors are members of one or several newly recognized large families of proteins: (1) molecules with 60 amino acids long repeats (H, CR1, CR2, C4BP, DAF); (2) proteins with 1,2-diacylglycerol membrane anchoring (DAF); (3) proteins with a heterodimer structure and preference for ligands containing the tripeptide arginine-glycine-asparagine (CR3, CR4). Recognizing the above mentioned regulators and receptors of the complement system as belonging to these protein families opens new perspectives for further genetic and functional research of mutual interest to complement and noncomplement scientists.

Amino Acid Sequence↗
PubMed1988

Importance of an 85 kDa membrane glycoprotein for a variety of cell-cell interactions.

The membrane molecule termed "7F7-antigen" has been found to be involved in several examples of cell-cell interactions. This 85 kDa glycoprotein with a protein core of about 55 kDa contains N-linked and O-linked carbohydrates. It has an isoelectric point of 8.0-8.5 and is expressed on 20% of peripheral blood mononuclear cells, 35% of peripheral blood B-cells, follicular dendritic cells and vascular endothelium. It is also expressed on activated T-cells and its expression on B-cells, fibroblasts and monocytes increases after treatment with PWM, interferon-gamma and after three days culture, respectively. The MAb 7F7 used to define this antigen inhibits the initiation of T-cell proliferation induced by anti-CD3, PHA, ConA and (weakly) allogenic stimulator cells, but does not affect the growth of IL-2 dependent T-cells and does not interfere with the killing of PHA-blasts by allogenic IL-2 dependent T-cells. 7F7 also inhibits the binding of C3-coated sheep erythrocytes to B-cells, the PMA-induced aggregation of U937 and the binding of activated T-cells to fibroblasts. The 7F7-antigen is expressed on some non-Hodgkin lymphomas of B-cell differentiation, particularly those with follicular structure, but not on Burkitt's lymphoma, ALL or carcinomas of various tissues. It is, however, found on fibrous tissue surrounding infiltrating carcinoma cells. The expression of a melanoma antigen, P3.58, which was shown to be identical to 7F7-antigen correlates with stage and spread of invasive melanoma. It was concluded that the 7F7-antigen, which is probably related to a previously described adherence molecule (ICAM-1), is of biological importance for the initiation of T-cell responses. With the possible exception of melanoma its expression on neoplastic cells in vivo is unlikely to be of importance for the spread of malignant disease.

Antigens, Neoplasm↗
PubMed1988

Lewis lung carcinoma cells enhance the synthesis of C3 and are opsonized by C3 secreted from murine macrophages.

We investigated the effect of Lewis Lung carcinoma cells on the production of C3 by murine macrophages and examined the capacity of secreted C3 to opsonize Lewis Lung carcinoma cells. C3 released in culture from macrophages obtained from tumor-bearing C57Bl/6 mice as well as from normal macrophages exposed to Lewis Lung carcinoma cells in vitro was measured by hemolytic assays and by Western blot. We found that contact with tumor cells in vivo as well as in vitro enhanced the amount of C3 secreted by murine macrophages by a factor of 2-3. The inflammatory agent carrageenan caused only a small increase in the amount of secreted C3. On Western blots of concentrated macrophage supernatants, there was partial cleavage of secreted C3 which was, however, not more pronounced in the case of C3 from tumor-stimulated macrophages than from normal macrophages. Supernatants from normal as well as tumor-stimulated macrophages were capable of opsonizing Lewis Lung carcinoma cells as shown by their capacity to bind human erythrocyte in an immune adherence reaction. Pretreatment of the tumor cells with a protease inhibitor, PMSF, inhibited the capacity of the tumor cells to bind C3, suggesting that a tumor cell-associated protease might be involved in the binding of C3 to the tumor cell surface.

Animals↗
PubMed1988

Selective induction of mononuclear phagocytes to produce neopterin by interferons.

Interferon-gamma (IFN-gamma) has been shown to be a potent inducer of neopterin secretion by human peripheral blood monocytes/macrophages (1). In this paper, it is shown that other known stimuli of monocytes (e.g., to secrete proteases or to migrate) such as zymosan-activated human serum, lipopolysaccharide, human C3/iC3 and zymosan coated with complement were unable to trigger monocytes/macrophages to release neopterin. Monocytes/macrophages could be stimulated solely by IFN-gamma (25 U/ml) and IFN-alpha at very high concentrations (10,000 U/ml). In the case of human peripheral blood mononuclear cells (PBMNC), basically the same pattern was observed. If however, in the buffer controls PBMNC showed some neopterin release, all stimuli triggered an increase of neopterin secretion: 10,000 U/ml IFN-alpha induced the same amount of secreted neopterin as did 25 U/ml of IFN-gamma. Both caused higher levels of neopterin secretion than ZAS, LPS and C3/iC3. Amongst the supernatants from PBMNC, only those which were obtained from cells activated with IFN-gamma or -alpha stimulated monocytes/macrophages to produce neopterin. Supernatants from lymphocytes activated with zymosan, lipopolysaccharide and interferon did not contain neopterin, nor did the latter induce monocytes/macrophages to generate and secrete neopterin. Antibodies against IFN-gamma inhibited the triggering effect of the supernatants except when generated by IFN-alpha at 10,000 U/ml. These results demonstrate that both interferons, IFN-gamma and IFN-alpha, the latter only at a 400-fold higher concentration, can trigger monocytes/macrophages directly to secrete neopterin. ZAS, LPS and C3/iC3 are weakly effective only on a mixture of lymphocytes and monocytes/macrophages, provided this cell mixture shows already a basic spontaneous neopterin release.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Comparison of Western blot (immunoblot) based on recombinant-derived p41 with conventional tests for serodiagnosis of human immunodeficiency virus infections.

To evaluate the performance of a serological test for human immunodeficiency virus type 1 (HIV-1) infections based on the use of a recombinant envelope gene-derived protein as the antigen, we caused expression of a 1.4-kilobase fragment of HIV.DNA that codes for the complete gp41 transmembrane protein in an Escherichia coli expression vector and used Western blots (WB; immunoblots) prepared with recombinant material (pEX-41) to detect antibodies to HIV-1. This test detected all 339 sera which were positive by a combination of conventional serodiagnostic assays and produced no false-positive results with 311 negative samples. Also no false-positive results were obtained with 20 sera from systemic lupus erythematosus patients which had high titers of cross-reactive autoantibodies. In six cases, the pEX-41 WB proved to be more sensitive than individual assays applied on their own, and in five cases it was even more sensitive than a combination of conventional assays. We tested 221 sera in both our pEX-41 WB and a commercially available recombinant enzyme immunoassay (EIA [Abbott]). The results were identical in 188 cases. A total of 27 sera containing antibodies to gp41 as demonstrated in the pEX-41 WB, as well as the Abbott recombinant EIA, had no antibodies to the recombinant core antigen as measured in the Abbott EIA. However, 25 of these sera did stain the 24-kilodalton band on a WB with purified virus. Six sera that were positive in all of the conventional confirmatory assays and reacted strongly with the pEX-41 WB did not recognize the surface antigen used in the Abbott recombinant EIA. We conclude that the use of WB prepared with recombinant-derived p41 offers a very sensitive and specific method to detect antibodies to HIV.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Structural and functional analysis of CR2/EBV receptor by means of monoclonal antibodies and limited tryptic digestion.

The receptor for the C3d fragment of the third component of complement, CR2, has recently been shown also to act as the receptor for the Epstein-Barr virus (EBV) and to be involved in the control of B-cell proliferation. In order to define functionally important domains on this molecule, we produced monoclonal antibodies to several distinct epitopes. CR2 was purified from a NP-40 lysate of human tonsils by a new method involving sequential chromatography on lentil lectin Sepharose 4B and DEAE-Sephadex and used to immunize mice. After fusion we obtained four stable hybridoma lines producing antibody to CR2. Specificity of these antibodies for CR2 was ascertained by immunofluorescence analysis on a panel of various cells known to possess CR2, by their reactivity in a recently described ELISA for C3 receptors, by Western blotting with purified CR2 and immunoprecipitation from 125I-labelled Raji cells. These four antibodies were found to recognize three distinct epitopes localized on the same fragments of 95,000, 72,000, 50,000, 32,000 and 28,000 MW obtained after mild tryptic digestion of CR2. The 72,000 MW fragment contains the binding site for C3d. Two monoclonal antibodies recognizing the same epitope did not inhibit the binding of C3d-coated sheep erythrocytes to Raji cells, whereas the other two antibodies against distinct epitopes did inhibit in the presence of a second antibody. All four monoclonal antibodies stimulated the proliferation of human peripheral blood B cells.

Antibodies, Monoclonal↗
PubMed1988

Individual epitopes of an 85,000 MW membrane adherence molecule are variably expressed on cells of different lineage.

The recently reported 85,000 MW membrane activation antigen, provisionally termed 7F7 antigen, is involved in the initiation of T-cell responses, in the binding of C3b-coated sheep erythrocytes to B cells and in the phorbol ester-induced aggregation of U937, suggesting that it represents a membrane molecule important for cell-cell adherence. Three new monoclonal antibodies were raised against the purified antigen and used to examine the expression of individual epitopes on cells of different lineage. All antibodies reacted with the purified membrane antigen on Western blots. Antibodies 7G2 and 7C6 reacted only weakly with activated T cells, although the 85,000 MW 7F7 antigen is recognized on T cells by antibodies 7F7 and 8B9. Whereas 7F7 and 8B9 inhibit the phorbol ester-induced aggregation of U937 and the attachment of phytohaemagglutinin (PHA)-activated T cells to fibroblasts, antibody 7G2 was without inhibitory effect. Four antibodies raised against the P3.58 glycoprotein, a melanoma-associated antigen with biochemical features similar to the 7F7 antigen were shown to react with the purified 7F7 antigen on Western blots. These four antibodies also failed to react with activated T cells. In addition, 7F7 bound to a L cell transfectant prepared with human chromosomal DNA which expressed the P3.58 antigen. The results indicate that the 7F7 antigen and the P3.58 melanoma antigen are identical, that some epitopes of this adherence molecule are differentially expressed on individual cell types and that one epitope, which is only weakly expressed on activated T cells, does not contribute to the role of the 7F7 antigen in some examples of cell-cell adherence.

Antibodies, Monoclonal↗
PubMed1988

Cell cycle control of a Burkitt lymphoma cell line: responsiveness to growth signals engaging the C3D/EBV receptor.

CR2, the receptor for the C3d fragment of the third complement component and for Epstein-Barr virus (EBV) has been shown, on mouse B cells, to be involved in the control of B-cell proliferation by acting as a receptor for macrophage-derived growth factors. We examined whether the growth of a Burkitt lymphoma cell line, RAJI, could be influenced by ligands of human CR2. In serum-free culture, purified human C3d, as well as three monoclonal antibodies to distinct epitopes on human CR2, were capable of enhancing the growth rate of RAJI cells two to five-fold. This effect could not be observed if even trace amounts of serum were present in the culture medium. Simultaneous addition of pairs of antibodies did not enhance the growth rate, suggesting that a particular engagement of CR2 may be critical in order to induce a stimulatory effect. These results indicate that in a homologous serum-free human B-cell system human C3d as well as monoclonal antibodies to human CR2 can induce B-cell proliferation and that CR2-mediated triggering of B cells can be induced via epitopes other than the C3d-binding site. In addition we conclude that--unlike normal human B cells--at least some human B-lymphoma cells respond to CR2-mediated stimuli in the absence of any T-cell derived factors. Therefore the control mechanisms exerted through CR2 must still be intact on these autonomously growing cells.

Antibodies, Monoclonal↗