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Biomedical subjects

G Hoffmann-Fezer

Publications and source records attributed to G Hoffmann-Fezer.

At least 19 recordsLinked to original sources
PubMed1998

Inhibition of the development of spontaneous autoimmune thyroiditis in the obese strain (OS) chickens by in vivo treatment with anti-CD4 or anti-CD8 antibodies.

The involvement of CD4+ and CD8+ T cells in pathogenesis of spontaneous autoimmune thyroiditis (SAT) in obese strain (OS) chickens has not been studied in depth until now. We depleted CD4+ or CD8+ T cells in OS chickens by treatment with murine monoclonal anti-CD4 or anti-CD8 antibodies at 3 day intervals beginning at hatching. The birds were killed at 19-25 days of age. Treatment with anti-CD4 antibody completely prevented SAT development, while treatment with anti-CD8 antibody partially inhibited SAT. These results show the critical role of CD4+ T cells in the development of SAT in OS chickens, and indicate that CD8+ T cells are also involved in SAT pathogenesis.

Age Factors↗
PubMed1997

Preclinical evaluation of biotin labeling for red cell survival testing.

Biotin labeling of red cells was tested in dogs as a preclinical study for cell survival. Red cells were labeled with either spacered Biotin-X-NHS (BxNHS) or water-soluble biotin compounds. After reinfusion, biotinylated red cells were detected in small blood samples (5 microliters) with flow cytometry. Improved BxNHS labeling allows an easy detection of positive red cells for almost 100 days, whereas labeling with watersoluble compounds-despite strong labeling during the first days-results in a decrease of label, which prevented a discrimation between labeled and negative cells after about 4 weeks. When biotin labeling of red cells was compared with 51Cr labeling, slopes of red cell survival were quite similar after the latter were corrected for elution. Survival slopes were linear, and the mean survival time was t = 93 d. In two blood-donor dogs the slopes of red cell survival where log linear and the mean survival time was t = 45 d. In conclusion, BxNHS, but not the water-soluble biotin compounds, is a good nonradioactive, nontoxic alternative for red cell survival studies. No health hazards are to be expected from the very low dose of Dimethylformamide, which is used as a solvent for biotin-x-NHS.

Animals↗
PubMed1996

Comparison of T-cell subpopulations in cats naturally infected with feline leukaemia virus or feline immunodeficiency virus.

T-cell subsets were studied by flow cytometry in 58 feline leukaemia virus (FeLV)-positive cats with naturally acquired FeLV infection to determine whether the changes in CD4+ or CD8+ T cell populations differed from those observed in 55 feline immunodeficiency virus (FIV)-positive cats with naturally acquired FIV infection. The sole criterion for inclusion into the study was seropositivity. Mean (SD) CD4+ T cell values of FeLV positive cats were decreased to 31.1 (8.0) per cent and their CD8+ T cell values were increased to 22.8 (6.3) per cent in comparison with uninfected control cats (37.9 [9.5] per cent CD4+; 15.2 [6.3] per cent CD8+). The CD4+/CD8+ ratio was reduced to 1.5 (0.7), compared with 3.0 (1.5) in 39 FeLV-and FIV-negative control cats. Differences from control values were significant, but there was no significant difference between CD4+ and CD8+ lymphocytes of FeLV-versus FIV-infected cats. These findings indicate that FeLV and FIV have similar effects on T lymphocyte subsets. Both retrovirus infections can induce immunodeficiency, both viruses infect a broad range of lymphohaemopoietic cells, despite having different primary target cells, and can induce the killing of lymphocytic cells in vitro. It is concluded that a decreased CD4+/CD8+ ratio is not restricted to FIV infections but may also occur in FeLV infection.

Animals↗
PubMed1996

Prevention of spontaneous autoimmune thyroiditis in the obese strain (OS) chickens by treatment with a monoclonal anti-CD4 antibody.

Untreated control OS chickens develop spontaneous autoimmune thyroiditis (SAT). In contrast, OS chickens treated with a monoclonal anti-CD4 antibody failed to develop SAT. The preventive effect of anti-CD4 antibody on SAT was associated with the marked depletion of CD4+ T-cells by anti-CD4 treatment. These results indicate that CD4+ T-cells play a crucial role in SAT of OS chickens.

Animals↗
PubMed1995

Rat monoclonal antibodies differentiating between the Epstein-Barr virus nuclear antigens 2A (EBNA2A) and 2B (EBNA2B).

Rat monoclonal antibodies were produced against the C-terminus of Epstein-Barr virus nuclear antigens 2A (EBNA2A) and 2B (EBNA2B) expressed as bacterial trpE fusion proteins. The initial screening was performed using a soluble bacterial extract containing the fusion proteins. Positive hybridomas were confirmed by immunofluorescence on SF158 (Spodoptera frugiperda) insect cells infected with recombinant baculovirus (Autographa californica nuclear polyhedrosis virus) and expressing the complete EBNA2A or EBNA2B genes. We selected a panel of antibodies which reacted either with both antigens or specifically with EBNA2A or with EBNA2B. The antibodies were extensively characterized using immunoprecipitation, Western blotting, epitope mapping on synthesized peptide segments of EBNA2A, immunocytology, and immunohistology on both cryostat sections and paraffin sections of AIDS-associated primary central nervous system lymphomas.

Animals↗
PubMed1995

Preferential TCR V beta 1 gene usage by autoreactive T cells in spontaneous autoimmune thyroiditis of the obese strain of chickens.

We studied T cell receptor variable beta (TCR V beta) gene usage by autoreactive T cells in spontaneous autoimmune thyroiditis (SAT) of obese strain (OS) chickens. Chicken alpha beta T cells may express either V beta 1 or V beta 2 genes, the products of which can be recognized by TCR2 and TCR3 monoclonal antibodies, respectively. Selective depletion of V beta 1+ or V beta 2+ T cells in OS chickens was accomplished by repeated injections of TCR2 or TCR3 antibodies into embryonic and 1-3-week-old chickens. The birds were killed at 20 days of age and their spleens and thyroid glands evaluated by immunohistochemistry. We found that V beta 1+ T cells preferentially infiltrated OS chicken thyroid glands. Antibody treatments resulted in a 41% reduction in frequency of V beta 1+, and a 87% reduction of the frequency of V beta 2+ cells in the circulation, and in a profound decrease of the respective T cells in spleens and thyroid glands. Selective suppression of V beta 1+ T cells partially inhibited SAT development in that thyroid-infiltrating cells and destruction of thyroid follicles were reduced by more than 50%. Thyroglobulin autoantibody serum levels were also reduced in V beta 1+ T cell-depleted OS chickens, whereas selective depletion of V beta 2+ T cells did not inhibit SAT development. These findings indicate preferential TCR V beta 1 gene usage by autoreactive T cells in SAT of OS chickens.

Animals↗
PubMed1995

Peripheral blood leukocyte grafts that induce human to mouse graft-vs.-host disease reject allogeneic human skin grafts.

Allogeneic graft-versus-host disease is characterized by skin, gut, and bile duct destruction by relatively few donor type lymphocytes. In contrast, we can now show that human-to-mouse xenogeneic graft-versus-host disease is characterized by vasculitis and tumor-like infiltrations of the murine lymphohemopoietic organs with many human CD25+, HLA-DR+, CD4+ lymphoblasts. Using the technique of serial transplantation, it appears that at least 90% of the human lymphoblasts were unreactive to murine tissues. It is demonstrated consistently that the donor type lymphoblasts induced typical allogeneic rejection of distantly located full thickness human unmatched fetal skin grafts. The fact that the human grafts show primary immune responses in vivo indicates that the graft-versus-host disease murine model may be suitable for vaccination studies.

Animals↗
PubMed1995

Suppression of normal and neoplastic human T cells with unconjugated monoclonal antibodies in SCID mouse chimeras.

The aim of this study was to establish a preclinical in vivo model to evaluate the suppressive effect of unconjugated anti-human T (CD3, 5, 7)-cell monoclonal antibodies (mAb) of mouse IgG2a or rat IgG2b isotype. Therefore, severe combined immunodeficient (SCID) mice were transplanted with human peripheral blood lymphocytes (PBL) of healthy donors (hu-PBL-SCID) or with neoplastic T cells of the human T-ALL cell line Jurkat. In preselected hu-PBL-SCID mice with substantial T cell chimerism single antibody injection caused prompt suppression of circulating human T lymphocytes within 2 days followed by occasional T cell recovery during the following weeks. Furthermore, antibody-mediated T cell suppression was measured by prolonged survival of SCID mice that had been injected with Jurkat cells preadapted to cause 100% mortality within 40 days. Injection of preadapted Jurkat cells caused fatal metastasis in lymphoid as well as non-lymphoid organs. The progression of leukemic cells was successfully suppressed when cells and anti-T cell mAb were given i.p. In contrast to control mice, tumor mortality of antibody-treated animals was delayed or completely suppressed. We conclude that SCID mice with reproducible human T cell chimerism are a relevant animal model to test the suppressive effect of anti-human T cell mAb in preclinical studies.

Animals↗
PubMed1994

A mouse model for the preclinical evaluation of immunosuppressive effector functions of human isotypes. The human IgG1 isotype is superior to IgG3.

Antibodies against T cells are widely used as immunosuppressive agents in clinical therapy. As effector functions of chimeric or humanized anti-T cell antibodies cannot be predicted in vitro, we compared T cell-depleting effects of human isotypes in vivo with their immunosuppressive consequences in a mouse BMT model. This system is based on chimeric antibodies with a mouse pan T cell specificity and human constant regions. To secure optimal immunosuppression, the specificity for Thy-1.2--one of the best-characterized T cell antigens--was selected, as Thy-1.2-specific antibodies prevent graft-versus-host disease in fully mismatched mice. Chimeric mouse anti-Thy-1.2 antibody with the human IgG1 Fc part was found to be equally effective in preventing graft-versus-host disease mortality as the highly protective anti-Thy-1.2 mouse IgG2a isotype, while human IgG3 was far less effective. This was not predictable by measuring the degree of T cell depletion in peripheral blood. T cell depletion in lymph nodes, however, exactly reflected the results obtained in the BMT system. In addition, this system offers the advantage of assessing the influence of reduced antigen density by using heterozygous Thy-1.2 mice.

Amino Acid Sequence↗
PubMed1993

Immunohistology and immunocytology of human T-cell chimerism and graft-versus-host disease in SCID mice.

Surprisingly little graft-versus-host disease (GVHD) has been observed in severe combined immunodeficient (SCID) mice injected intraperitoneally (IP) with human blood lymphocytes (hu-PBL-SCID), which raised the question as to whether GVHD in such a distant species is sporadic or suppressed because of immunologic reasons. After screening for blood T-cell chimerism, we hereby describe generalized lethal xenogeneic human GVHD in unconditioned SCID chimeras, which resembles GVHD in SCID mice injected with allogeneic lymphocytes. We adapted an immunocytochemical slide method for minute cell numbers, which allowed us to follow, by multimarker phenotyping of weekly mouse-tail bleeds, the chimeric status of 100 hu-PBL-SCID injected with 10(7) or 10(8) hu-PBL of Epstein-Barr virus- (EBV-) donors. More than half of the mice showed no or less than 2% T cells. However, 13% to 21% developed substantial blood T-lymphocyte chimerism (10% to 80% human CD+ cells) and high mortality. Immunohistology showed more human CD8+ than CD4+ T cells in the splenic white pulp. The cells developed HLA-DR activation markers and infiltrated the red pulp where human B cells also appeared. Expression of activation and proliferation markers increased within 5 to 6 weeks. Many human CD3+ cells were also found in the portal triads of the liver and in the lung, pancreas, and kidney. The thymus also became heavily infiltrated. The intestines and skin of hu-PBL-SCID were less infiltrated by donor cells than in SCID with allogeneic GVHD. The tongue contained almost no human T cells. Our data show that a relatively low overall incidence of human xenogeneic GVHD, even when high numbers of human PBL are injected, is the consequence of a dichotomy between mice with no or transient T-cell chimerism and a minority of mice with high-blood T-lymphocyte chimerism and GVHD mortality.

Animals↗
PubMed1993

Biotin labeling as an alternative nonradioactive approach to determination of red cell survival.

Biotin labeling of red cells was studied using different approaches to see if biotinylation is a useful label for determination of erythrocyte survival. Mouse red cells were labeled with biotin, either in vivo by injection or in vitro. In vivo labeled red cells were followed up in some mice without transfusing the labeled erythrocytes. Furthermore, in vivo labeled as well as in vitro labeled red cells were transfused into syngeneic mice. The biotin label allows an easy discrimination between labeled and unlabeled red cells during FACS analysis, and it is relatively stable for at least 50 days. All the three different approaches give similar results. Mean red cell life spans of in vivo or in vitro labeled red cells either transfused or followed up in vivo were between 44 and 52 days (T50 mean 23.9 days) when red cell destruction was assumed to be only a result of senescence. Mean red cell life spans were between 8 and 18 days (T50 mean 9.5 days) when a random destruction independent of red cell age was suggested. All the survival slopes are neither simple linear functions of time nor logarithmic functions, but they show an overlay of linear function by a logarithmic function where the components of both are unknown.

Animals↗
PubMed1993

Identification and characterization of a mouse monoclonal antibody (M10) directed against canine (dog) CD8+ lymphocytes.

Monoclonal antibodies (mAb) were produced by immunizing BALB/c mice with non-adherent dog lymphocytes. M10 was specific for a subset of dog lymphocytes. M10 belonged to the IgG1 subclass and reacted with 26% of dog peripheral blood lymphocytes, 24% of spleen lymphocytes, 81% of thymus cells, 1.2% of bone marrow cells (5.8% of bone marrow lymphocytes) and 23% of PHA-stimulated lymphocytes. Immunohistology of snap-frozen thymus and spleen showed that the spleen B-cell area stained negative, whereas the spleen T-cell area and the thymus medulla exhibited positive reaction in 20-30%. The thymus cortex was strongly positive. M10 diminished cell lysis by 58% in cell mediated lysis assays (CML). Immunoblot assays revealed that M10 recognized an antigen with a molecular weight of 76 kD under non-reducing and 33 kD under reducing conditions. Finally, M10 bound to a canine CD8 alpha transfected rat T-cell line (NB2). These findings characterize M10 as an antibody directed against the dog CD8 antigen.

Animals↗
PubMed1993

In vivo depletion of chicken T-cell subsets.

In the chicken three types of T-cell receptors can be defined by monoclonal antibodies TCR1, TCR2 and TCR3, which recognize gamma delta T cells, and V beta 1- and V beta 2-expressing alpha beta T cells, respectively. In the present report we have analysed means of selectively depleting the gamma delta T cells and the V beta 1+ alpha beta T cells. gamma delta T cells, which represent up to 66% of all T cells in blood of a 6-month-old chicken, can be effectively depleted by neonatal thymectomy (Tx) to levels as low as 1%. Immunohistology demonstrates a similar depletion in lymphoid organs while intestinal epithelium-associated gamma delta T cells are affected by Tx to a lesser extent. V beta 1-bearing alpha beta T cells, which comprise about 80% of the alpha beta T cells, were depleted by embryonic and neonatal injection of the TCR2 antibody. In the thymus such treatment depleted only the V beta 1+ alpha beta T cells with high density expression of T-cell receptor. Therefore, we thymectomized TCR2-treated animals in order to prevent development of mature V beta 1+ alpha beta T cells from the low density immature thymocytes. Treatment of chickens with a total of 22 mg of TCR2 antibody plus Tx reduced V beta 1+ alpha beta T cells from an average of 65% to 10% of all T cells. In these TCR2 antibody-treated animals the V beta 2-expressing alpha beta T cells become the predominant type of T cell (average 85%).

Age Factors↗
PubMed1992

Peritoneal sanctuary for human lymphopoiesis in SCID mice injected with human peripheral blood lymphocytes from Epstein-Barr virus-negative donors.

The successful engraftment in SCID mice of intraperitoneally (i.p.) injected human lymphocytes (hu-PBL-SCID) and the failure of intravenously injected peripheral blood lymphocytes (PBL) directed the present study to investigate the early events of donor cell proliferation in the peritoneal cavity. We found focal lymphocyte engraftment together with histio-monocytic interleukin (IL)-6+ cell phenotypes which must have been transferred with the human cell inoculum, which could explain certain immune functions observed in hu-PBL-SCID chimeras. Following i.p. injection of 10(8) PBL, human cells suspended in peritoneal fluid as well as those adherent to the serosal peritoneum and abdominal organs were investigated by immunocytology and immunohistology. Human cells were found to form foci consisting predominantly of proliferating human lymphoblastoid CD3+ cells, which were mostly activated HLA-DR+ CD8+ lymphocytes. Among the lymphoid cells larger epithelioid-like cells were found to belong to the monocytic series and to stain strongly with anti-HLA-DR and anti-CD11c antibodies. Some of these cells were also positive with anti-ICAM and anti-IL-6. Congenic as well as allogeneic mouse PBL, injected i.p. into SCID mice, temporarily produced analogous foci, which shifted later on to foci similar in appearance to milky spots. However, the human cell foci appeared less compact, more closely resembling in vitro-culture soft agar colonies. It is possible that cytokines in the human histio-monocytic cells of the foci may have a feeder effect on the human lymphocytes and be a prerequisite for proliferation of human PBL in SCID mice. The observed early HLA-DR activation of human lymphocytes in the peritoneal foci could reflect triggering of immune reactions like xenogeneic graft-versus-host reactions in the peritoneal site, where the human CD11c+ HLA-DR+ histio-monocytic cells may act as antigen-presenting cells.

Animals↗
PubMed1992

Use of two virustatica (AZT, PMEA) in the treatment of FIV and of FeLV seropositive cats with clinical symptoms.

In the present study the therapeutic efficacy and the side effects of two antiretroviral compounds used in human acquired immunodeficiency syndrome (AIDS) research, 3'-azido-2',3'-dideoxythymidine (AZT, zidovudine, Retrovir) and 9-(2-phosphonylmethoxyethyl)adenine (PMEA), were investigated in the treatment of cats naturally infected with feline immunodeficiency virus (FIV) and cats naturally infected with feline leukemia virus (FeLV). AZT was administered subcutaneously at a dose of 5 mg kg-1 body weight every 12 h and PMEA was administered subcutaneously at a dose of 2.5 mg kg-1 body weight every 12 h during a 3 week hospitalization. The therapeutic efficacy of both compounds was investigated. There was a stronger potency of PMEA than of AZT on the regression of stomatitis in FIV and in FeLV infected cats. In addition, in FIV infection PMEA had a stronger effect on the improvement of the general clinical status. Both antiretroviral compounds were potent agents to improve the immunologic status of FIV infected cats by raising the CD4/CD8 ratio. In FeLV infection PMEA and AZT appeared to reduce antigenemia. The hematological side effects caused by PMEA were severe and stronger than those of AZT. Therefore the advantage of PMEA in clinical and immunologic improvement was diminished by the hematologic disorders, which do not allow long term treatment with this drug in the dose used.

Adenine↗
PubMed1992

Decline in CD4+ cell numbers in cats with naturally acquired feline immunodeficiency virus infection.

T-cell subsets were studied by fluorescence-activated cell sorter analysis in 57 feline immunodeficiency virus (FIV)-seropositive cats with naturally acquired FIV infection to see whether CD4(+)-CD8+ alterations were comparable to those observed in human immunodeficiency virus-infected patients. CD4+ values were decreased and CD8+ values were increased. The CD4+/CD8+ ratio was reduced to 1.6, compared with 3.3 in 33 FIV-seronegative control cats. Variance analysis of data showed a significant influence of FIV seropositivity, sex, and spaying of female cats on CD4+ values. CD8+ values were significantly influenced by FIV seropositivity, age, and breed. These findings indicate a similarity between FIV and human immunodeficiency virus infections, as far as alterations of T-cell subsets are concerned.

Age Factors↗
PubMed1991

T cells expressing the V beta 1 T-cell receptor are required for IgA production in the chicken.

While alpha beta T cells in mammals may express one of many variable (V) gene families in the beta locus, chickens have only two V beta gene families. The avian V beta 2+ T cells are recognized by the T-cell receptor 3 (TCR3) monoclonal antibody and V beta 1+ T cells are recognized by the TCR2 antibody, which we used to selectively suppress development of V beta 1+ T cells in order to examine their functional role. Suppression was accomplished by multiple injections of anti-TCR2 antibodies beginning in embryonic life and perpetuated by thymectomy 8 days after hatching. Young birds thus depleted of V beta 1+ T cells had greater than normal numbers of V beta 2+ T cells and appeared as healthy as thymectomized and untreated controls. While production of IgM and IgG antibodies was unimpaired, IgA antibody production was severely compromised in the V beta 1-depleted birds. The levels of secretory IgA in bile and lung lavage fluid were reduced 1000- to 10,000-fold and secretory IgA antibodies were not produced in response to mucosal immunization. B-cell production of IgA antibodies thus appears to require T cells expressing the V beta 1 genes, whereas T cells that express the V beta 2 genes lack this capacity.

Animals↗