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Biomedical subjects

M Waer

Publications and source records attributed to M Waer.

At least 145 records · Page 8Linked to original sources
PubMed1990

Angiotensin-converting-enzyme inhibitors and anaphylactoid reactions to high-flux membrane dialysis.

In a retrospective study, 9 of 236 haemodialysis patients treated with high-flux polyacrylonitrile 'AN 69' membranes were found to have had anaphylactoid reactions. Treatment with angiotensin-converting-enzyme (ACE) inhibitors had been recently started in all 9 affected patients; only 5 of 227 unaffected patients had been treated with ACE inhibitors, and anaphylactoid reactions disappeared after discontinuation of ACE inhibitors.

Adult↗
PubMed1990

Induction of transplantation tolerance in mice across major histocompatibility barrier by using allogeneic thymus transplantation and total lymphoid irradiation.

The use of allogeneic thymus transplantation as a means of inducing tolerance across MHC barriers was investigated in thymectomized, total lymphoid irradiated BALB/c mice. In 90% of the animals long term outgrowth of histologically normal C57BL thymus grafts was observed. None of the latter animals was chimeric. All thymus graft-bearing mice showed specific nonresponsiveness for C57BL MHC Ag in mixed lymphocyte reaction and cell-mediated lympholysis. Spleen cells of the C57BL thymus-bearing mice were unable to induce lethal graft-vs-host disease in neonatal (BALB/c X C57BL) F1 mice but provoked a vigorous graft-vs-host disease reaction in (BALB/c x C3H) F1 neonates. Tolerant mice permanently accepted C57BL heart and pancreas grafts, but all rejected C3H grafts. Induction of tolerance of BALB/c pre-T cells through allogeneic thymus graft and/or specific suppressor cells seems to be involved. The present model offers new opportunities to study thymocyte maturation in a fully allogeneic environment and may yield applications for clinical organ transplantation.

Animals↗
PubMed1990

Determination of mixed chimerism by a simple flow cytometry method.

A simple, sensitive and accurate method was developed to determine the level of lymphoid chimerism in bone marrow-transplanted rodents. The method is based on flow cytometry using polyclonal alloantisera and labeled second step anti-IgG antibodies. Using mixtures of spleen cells from different mouse strains, it was demonstrated that low levels of chimeric cells (less than 1%) could easily be detected. Moreover, using two-color fluorescence analysis, the level of chimerism could also be determined in subpopulations of lymphoid cells, e.g., CD4 or CD8 cells and was found to be identical to the results obtained in unseparated lymphoid populations. The method was compared to the complement dependent cytotoxicity assay (CDCA) and to the flow cytometric determination of chimerism using labeled monoclonal antibodies against specific MHC antigens. CDCA was found to be more labor intensive and could only estimate the composition of the cell mixtures without detecting low levels of chimerism (less than 5%). The results of flow cytometry, using directly labeled monoclonal antibodies or polyclonal antibodies with second step reagents, were identical. It is concluded that, due to its simplicity and high sensitivity, the method described permits reliable determination of the level of mixed chimerism in rodents and is an excellent alternative when no anti-MHC mAbs are available.

Animals↗
PubMed1990

Measurement of alloantibody by flow cytometry.

A new method based on flow cytometry has been developed to determine IgG alloantibodies in the serum of immunized rodents. The method utilizes target lymphoid cells, diluted serum and labeled anti-mouse or anti-rat IgG antibodies. In serum from highly immunized animals alloantibodies could be demonstrated up to a dilution of (3 x 10(4))-1 which makes the test approximately 300 times more sensitive than a simultaneously performed complement-dependent cytotoxicity assay (CDCA). Moreover a linear relationship between the amount of alloantibody and the log value of the mean fluorescence of the target cells was found. This linearity permits the comparison of alloantibody production between individual samples by comparing the mean fluorescence values. The reproducibility of the assay was excellent since the coefficients of variation for all dilutions were less than 15%. By using two-color fluorescence the method can discriminate alloantibodies directed against class I and class II MHC antigens. Finally, in addition to its high sensitivity and good reproducibility, the method was found to be at least twice as fast as CDCA.

Animals↗
PubMed1990

Induction of mixed lymphocyte reaction nonresponsiveness after chimeric thymus transplantation.

Discussion still continues regarding whether self-tolerance is imparted within the thymus by the thymic epithelial cells (TEC) or by the bone marrow-derived (BMD) dendritic cells and macrophages. Many experiments suggest that BMD cells may be the major cells responsible for inducing tolerance within the thymus. In order to address this question and to see whether thymus chimerism could play a role in establishing transplantation tolerance, we looked in the present experiments at the induction of in vitro tolerance after transplantation of chimeric thymuses. Chimeric thymuses were constructed by injecting T-depleted C3H (H2k) bone marrow into lethally irradiated BALB/c (H2d) mice and were thus composed of TEC of BALB/c and BMD cells of C3H origin, something which was verified with immunoperoxidase staining. Subsequently, chimeric thymuses were transplanted into thymectomized BALB/c mice that were lethally irradiated and reconstituted with T-depleted syngeneic BALB/c bone marrow. In 8 out of 11 BALB/c mice this procedure was successful, and in all chimeric thymus graft-bearing mice, specific tolerance for C3H (H2k) antigens was documented in the mixed lymphocyte reaction (MLR). These experiments thus show that: (1) immunological tolerance can be imparted by BMD cells in the thymus and (2) the presence of chimerism within the thymus could be one of the mechanisms involved in the establishment or maintenance of transplantation tolerance.

Animals↗
PubMed1990

Mechanisms involved in the differential recovery of CD4 and CD8 T-lymphocytes after local irradiation in mice.

The mechanisms involved in the differential recovery of CD4 (helper/inducer phenotype) and CD8 (cytotoxic/suppressor phenotype) T-lymphocytes after fractionated local irradiation were investigated. In mice, a better recovery of CD4 cells than of CD8 cells was found, while the reverse has been described in humans. Differences in radiosensitivity between CD4 and CD8 mouse splenocytes could not be found. No sequestration of CD8 cells in irradiated tissues could be demonstrated. Irradiation of the thymus did not influence the observed immune changes. Altered thymic production of CD4 and CD8 cells could be excluded by intrathymic injection of FITC (fluorescein isothiocyanate). Hindlimb and tail irradiation did not induce changes in the morphology of the thymus and the phenotype of the thymocytes. These results suggest that the differential recovery of CD4 and CD8 T-lymphocytes after local irradiation is determined by extrathymic factors in man and mice, and that the observed differences in immune recovery between man and mice are due to defective thymic function in the former and normal function in the latter.

Animals↗
PubMed1990

Effects of thymus irradiation on the immune competence of T cells after total-lymphoid irradiation.

Spleen cells from mice receiving TLI, with or without thymus shielding, were investigated for in vitro and in vivo defects. At 4-6 weeks after irradiation spleen cells of both groups showed a normal number of Thy1 (T cells), L3T4 (CD4 positive T cells) cells, and an absence of natural suppressor cells. Splenocytes of the nonthymic shielded TLI group were not able to mount either a normal in vitro response (in MLR or PHA) or an in vivo graft-versus-host-disease reaction when injected into lethally irradiated adult allogeneic recipients or into neonatal F1 hybrids. This was in contrast to the normal immune capacity of spleen cells from the thymus shielded group that gave normal MLR and PHA tests in vitro and provoked GVHD in vivo. Thymuses recovered from mice receiving TLI with or without thymic shielding were however equally efficient in restoring the immune capacity after transplantation into neonatally thymectomized mice as measured by the PHA assay. Thymic irradiation is therefore necessary but not sufficient for creating long-lasting immune defects after TLI.

Animals↗
PubMed1990

Duplex Doppler evaluation of renal allograft dysfunction: Doppler signal quantitation and pathologic correlation.

The value of quantitative duplex Doppler sonography in discriminating the different possible causes of renal transplant dysfunction was prospectively studied in 60 patients during 65 episodes of renal function impairment. Final diagnosis at histology was acute rejection (n: 30), acute tubular necrosis (n: 4), cyclosporin nephrotoxicity (n: 16) and chronic rejection (n: 15). Duplex sonography was done the day a percutaneous biopsy was taken and before any therapy was started. Arterial Doppler signals obtained from the segmental, interlobar and arcuate arteries were both morphologically and quantitatively analysed. For quantitative analysis we used the resistive index as proposed by Pourcelot on the one hand, and introduced a variant resistive index on the other hand. Morphological analysis yielded no discriminative value. Comparing both quantitative methods--the resistive index of Pourcelot and the variant resistive index--clearly higher specificities--71% using the variant resistive index, 28% using the resistive index of Pourcelot--for excluding acute rejection from the other possible causes of renal function impairment could be achieved. A nephrectomy was done on 7 patients with severe transplant dysfunction. Microangiographies performed on these nephrectomy specimens were correlated with previous Doppler studies and with histology.

Graft Rejection↗
PubMed1989

Immunologic changes after loco-regional radiotherapy and fractionated total body irradiation (TBI) in mice.

The immunologic effects of fractionated irradiation to both hind limbs and the tail of adult (2.5-3 months old) male Balb/c mice were investigated. A dose of 34 Gy given in 17 fractions of 2 Gy, 1 fraction per day, 5 days per week, was delivered with a 60Co source. A significant decrease of the total splenocyte count (29% of control value) and of the PHA(phytohemagglutinin)-induced proliferation of T cells (22% of control value) was found immediately after irradiation. Both parameters normalized within 30 days after irradiation. Immediately after irradiation, the MLC (mixed lymphocyte culture) was supranormal (126% of control value), dropped to 45% 1 week later, and normalized within 1 month after radiotherapy. The NK (natural killer) activity was significantly decreased only the first week after loco-regional irradiation, while the LAK (lymphokine activated killer) activity was not altered at all. The percentage of goat-anti-mouse+ cells (mainly B lymphocytes) was not changed immediately after loco-regional irradiation, but rose to supranormal values (175% of control level) 3 months after irradiation. A persistent decrease of the percentage and the absolute numbers of the Lyt2+ cells (= CD8+ cells, suppressor/cytotoxic phenotype) was observed up to 3 months after irradiation, while the percentage of L3T4+ cells (= CD4+ cells, helper phenotype) remained normal for the total follow-up. No differences in allogeneic skin graft survival could be demonstrated between irradiated and control animals. The observed immunological effects could not be explained by the scatter irradiation to the whole body as total body irradiation (TBI) administered in a dose and dose rate similar to the scatter dose did not result in persistent immunologic changes. No dose-rate effect could be demonstrated in a low dose fractionated total body irradiation schedule. A total body irradiation similar to the scatter dose in humans did not result in significant immunologic changes.

Animals↗
PubMed1989

Listeria monocytogenes meningitis.

The history and findings of all patients with Listeria meningitis admitted to the University Hospital of Leuven from 1967 to 1987 were reviewed. Listeriosis during pregnancy or the perinatal natal period was not considered. Predisposing conditions in these 23 patients included renal transplants (9), immunosuppressive therapy (2), diseases of the lympthoreticular system (3) and chronic alcoholism (1). One man had an inversed T4/T8 ratio. In 7 patients no underlying disorder was detected. Disease onset may be acute or subacute. There are no clinical features distinguishing Listeria meningitis from other acute bacterial meningitides. The number of leukocytes in the CSF varied from 3 to 3700, most often with a predominance of mononuclear cells. A decrease of the glucose level in the CSF was not always present. The initial gram stain was often unrevealing and it took up to 4 days for CSF cultures to become positive. Blood cultures were often important for the identification of the organism.

Adolescent↗