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Biomedical subjects

V Kiefel

Publications and source records attributed to V Kiefel.

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

Pregnancy-maintaining antibodies: workshop report (Giessen, 1988).

To analyse the nature of antibodies which are purported to be essential for the maintenance of normal human pregnancy, six centers participated in a workshop of "blind" tests on 19 allosera. Fc-receptor dependent assays detected antibodies with specificity only for HLA. In addition to cytotoxic antibodies, the Fc-receptor dependent immune phagocytosis inhibition test revealed two non-cytotoxic alloantibodies with HLA specificity. These antibodies had high titers and may, therefore, be essentially non-cytotoxic. Murine monoclonal antibodies to HLA-A, B, C or DR (W6/32 and 2MC3) were used to evaluate the methods. These antibodies inhibited immune rosette formation as well as immune phagocytosis. Diluted to concentrations below the threshold of complement-dependent cytotoxicity, the monoclonal antibodies still inhibited the mixed lymphocyte reaction and the immune phagocytosis. A human monoclonal immunoglobulin M with specificity for monomorphic non-HLA lymphocyte antigens inhibited the mixed lymphocyte reaction. The immune rosette inhibition test exhibited several false positive reactions, e.g. three out of four with a serum that did not contain alloantibodies to blood cells. Non-cytotoxic antibodies were therefore rare in the selected sera of the workshop and they exhibited HLA specificity only. No participant was able to identify pregnancy-maintaining non-HLA-antibodies.

Abortion, Habitual↗
PubMed1989

Discrimination of antibodies against antigens of different MHC loci in human sera by monoclonal antibody-specific immobilization of leukocyte antigens.

To detect human antibodies against antigens of different major histocompatibility complex loci, particularly of class II specificity, a newly developed enzyme immunoassay for platelet antibodies was adapted for the use of lymphocytes as target cells. Peripheral blood lymphocytes, phytohemagglutinin-stimulated T cells, or Epstein-Barr virus-transformed B cells were simultaneously incubated with a monomorphic class- or locus-specific monoclonal antibody and the human antibody to be investigated. After solubilization, cell lysates were transferred to an enzyme-linked immunosorbent assay tray coated with a goat anti-mouse Ig antibody. Following immobilization of the monoclonal antibody/antigen complexes, human major histocompatibility complex antibodies were detected by addition of enzyme-labeled goat anti-human Ig. By means of this technique human antibodies against different major histocompatibility complex molecules present in the same sample could be clearly distinguished. Application of the monoclonal antibody-specific immobilization of lymphocyte antigens assay is presented by several examples. Of these, identification of DP-specific antibodies as well as serological DP typing are of particular interest.

Antibodies, Monoclonal↗
PubMed1989

Human platelet alloantigens Bra/Brb are expressed on the very late activation antigen 2 (VLA-2) of T lymphocytes.

We report the molecular localization of the human platelet alloantigens Bra/Brb on activated T lymphocytes. By radioimmunoprecipitation anti-Bra precipitated two proteins from T lymphocytes of Br(a+) donors after long-term activation (24 days), but not from resting or short-term-activated T lymphocytes (4 days). No bands could be precipitated with anti-Bra from T lymphocytes of Br(a-) donors, but the same two bands were seen with anti-Brb. The apparent molecular weights of unreduced molecules were 155 and 130 kDa, respectively. Monoclonal antibody Gil4 directed against an epitope on the platelet membrane glycoprotein Ia/IIa complex precipitated the same two bands with long-term-activated T lymphocytes, whereas MoAb TS2/7 directed against very late antigen (VLA)-1 molecules precipitated two bands with Mr 180 and 130 kDa (alpha 1 beta heterodimer). The physicochemical properties of these two bands precipitated by anti-Bra, anti-Brb or monoclonal antibody Gil4 with molecular weights of 155 and 130 kDa, respectively, correspond to VLA alpha 2 and beta chains and fit defined criteria for the VLA-2 antigen. These results were corroborated by an assay employing monoclonal antibody for antigen immobilization showing that Bra and Brb antigens were present only on long-term activated T lymphocytes. Our results provide evidence for the expression of the Bra/Brb platelet alloantigen system on VLA-2 antigens of activated T lymphocytes and demonstrate a genetic polymorphism of VLA-2 molecules on both cell lines.

Antigens, Differentiation↗
PubMed1989

Immune thrombocytopenia more than a year after allogeneic marrow transplantation due to antibodies against donor platelets with anti-PlA1 specificity: evidence for a host-derived immune reaction.

We report on a male patient transplanted from his HLA-matched sister for Ph1-chromosome positive chronic myelogenous leukaemia who developed immune thrombocytopenia more than 1 year after transplantation. The platelet antibody reacted with the platelet specific antigen PlA1 on donor platelets, and also on recipient platelets after engraftment. A presumed host-versus-donor induced thrombocytopenia was supported by Southern blot analysis using a Y-chromosome specific probe demonstrating residual host-origin cells in the patient's excised spleen.

Adult↗
PubMed1989

Immune-mediated agranulocytosis related to drugs and their metabolites: mode of sensitization and heterogeneity of antibodies.

Two major unresolved problems in drug-related immune agranulocytosis are understanding the mechanism by which sensitization takes place in vivo, and verification of the diagnosis. Using a sensitive, competitive enzyme-linked immunoassay (ELISA) we were able to characterize the causative antibodies in 13 patients with drug-related agranulocytosis [metamizole (n = 5), penicillin (n = 5), dimethylaminophenazone (n = 1), propyphenazone (n = 1) and diclofenac (n = 1)]. Irrespective of the causative drug, the majority of patients appear to have developed autoantibodies (aab) in addition to drug-dependent antibodies (ddab) of the IgG and/or IgM classes. In all cases related to metamizole, and in the single case related to diclofenac, the ddab appeared to recognize only metabolites of the drug since they were reactive in the presence of ex vivo antigens (urine from individuals receiving therapeutic levels of the drugs), but not the native drugs. Only a few ddab were reactive with granulocytes pretreated with the drug (cell-drug complexes); the majority of ddab could not be detected unless the drug or ex vivo antigen was added to the incubation mixture as well as the solution used for subsequent washes. Our results indicate that drugs and/or their metabolites interact with target cells and thereby directly function as immunogenic haptens, even when the drugs do not bind tightly to the cells.

Adolescent↗
PubMed1989

Immunochemical characterization of the new platelet alloantigen system Bra/Brb.

We report the immunochemical characterization of the new platelet-specific alloantigens Bra and Brb. Bra antibodies were from mothers of children with neonatal alloimmune thrombocytopenia (NAIT), and anti-Brb was found in the serum of a polytransfused patient. By radioimmunoprecipitation, anti-Bra and anti-Brb precipitated two proteins with apparent relative molecular masses in sodium dodecyl sulphate-polyacrylamide gel electrophoresis of 155,000 and 130,000 under non-reduced conditions, and of 165,000 and 148,000 under reduced conditions. In two-dimensional polyacrylamide gel electrophoresis, the two bands moved with isoelectric points ranging from 5.2 to 5.4 and from 4.5 to 4.7, respectively. These features fulfil previously defined criteria for platelet membrane glycoproteins (GP) Ia and IIa. The results were supported by data obtained by an assay employing monoclonal antibody (mab)-specific immobilization of platelet antigens (MAIPA). By this technique, Bra and Brb antigens could be immobilized by mabs specific for the GP Ia/IIa complex (mab Gi 14) or a mab specific for the very late antigen-2 (mab 12 F1), but not by a mab specific for GP IIb/IIIa complex (mab Gi3). Furthermore, platelets from a thrombasthenic patient with complete absence of GP IIb/IIIa expressed the Brb antigen normally as shown in MAIPA; this antigen could be immunoprecipitated with anti-Brb and was identical to that of normal platelets. This confirms that the antigens of the Br system are not associated with the GP IIb/IIIa complex. By direct binding studies using mabs Gi3 and Gi14, we calculated that 51,500 +/- 3900 molecules of anti-GP IIb/IIIa and 6,470 +/- 500 molecules of anti-GP Ia/IIa were bound per platelet at saturation. Our results provide evidence for the first platelet-specific alloantigen system residing on the GP Ia. The difficulty in detecting anti-Bra and anti-Brb by direct binding assays may be related to the small number of GP Ia/IIa complexes on platelets.

Antibodies, Monoclonal↗
PubMed1989

HLA-DP antigens in patients with chronic autoimmune thrombocytopenia (AITP).

AITP, a disease with well-defined autoimmune character, has been previously studied for a possible HLA association. However, no such association with antigens of the A, B, C or DR loci was found. As this does not exclude a possible association with HLA-DP antigens, we have investigated 36 patients with AITP for DP w1, w2, w3, w4 and w5 by primed lymphocyte typing using locally derived as well as the original DP reagents as used in the 9th International Histocompatibility Workshop. Comparison of antigen frequencies with those of 254 healthy controls revealed an increased frequency of DPw5 in the patient group which, however, was not statistically significant. Other discrepancies were not observed.

Adolescent↗
PubMed1989

Posttransfusion purpura associated with an anti-Bak.

We describe a 46-year-old white woman with typical clinical features of posttransfusion purpura (PTP) whose serum held a platelet-specific alloantibody reactive with an antigen antithetical to Baka, i.e. anti-Bakb. The specificity of the antibody was confirmed by family analysis, a population study (expected versus observed gene frequency: 0.3651 versus 0.3984; n = 105) and localization of the antigen on glycoprotein IIb in radioimmunoprecipitation. Typing of family members and blood donors for platelet antigens disclosed that the patient had been preimmunized by two blood transfusions in 1981, while fetomaternal incompatibility for Bakb was ruled out (her three children and their father were Bakb negative). Treatment of PTP with corticosteroids and platelet transfusions was ineffective, but infusion of high-dose intravenous IgG resulted in a rapid increase in the platelet count.

Antigens, Human Platelet↗
PubMed1989

Quantitation of platelet antigens after chloroquine treatment.

The effect of chloroquine treatment on the expression of various platelet antigens was studied. For this purpose, the binding of several human platelet-reactive antibodies (polyspecific HLA antibodies; platelet-specific PlA1, PlA2, Baka antibodies; platelet autoantibodies) and of murine monoclonal antibodies specific for epitopes on the glycoprotein (Gp) complexes IIb/IIIa or Ib/IX were quantitated by means of a competitive enzyme-linked immunoassay (CELIA) using fresh and stored chloroquine-treated platelets. We found that HLA antigens were substantially removed from platelets following chloroquine treatment (confirming earlier results) while platelet-specific antigens on the Gp complex IIb/IIIa were but little affected. Epitopes on the Gp complex Ib/IX did not show any alteration. Storage of chloroquine-treated panel platelets known to interfere with immunofluorescence had no effect on quantitative IgG determinations by CELIA. We conclude that chloroquine treatment of platelets is practicable for platelet antibody analysis, but exerts its effect unspecifically and requires cautious interpretation.

Antibody Specificity↗
PubMed1989

The Bra/Brb alloantigen system on human platelets.

Anti-Bra was first identified in four cases of neonatal alloimmune thrombocytopenia (NAIT). The antigen Bra is localized on the glycoprotein Ia/IIa complex of platelets. Anti-Bra can best be detected by a glycoprotein-specific immunoassay using monoclonal antibodies for antigen immobilization (MAIPA assay) and radioimmunoprecipitation (RIP). Recently, we have identified sera from two polytransfused patients that contain an antibody that recognizes Brb, the allele of Bra. Family studies show that both antigens are inherited as autosomal codominant characters. The gene frequency of the new allele Brb is 0.888. Approximately 2,000 anti-Bra binding sites are present on homozygous platelets and 1,000 on heterozygous platelets. Our findings provide evidence for the first polymorphism observed on the glycoprotein Ia/IIa complex. Immunization against these alloantigens is implicated in NAIT and poly-transfused patients.

Antibodies, Monoclonal↗
PubMed1989

[Thrombocyte-specific antigens/antibodies and their clinical importance].

This review updates our present state of knowledge with regard to platelet-specific alloantigens, i.e. Zwa/Zwb (PlAl/PlA2), Baka/Bakb, Koa/Kob, Yuka/Yukb (Penb/Pena), Bra/Brb, Nak, Sib, and summarizes relevant immunogenetical and biochemical data. The impact of corresponding platelet-specific antibodies in clinical conditions such as neonatal alloimmune thrombocytopenia, posttransfusion purpura, and the refractory state of platelet transfusions is reviewed with particular emphasis on our own case material.

Autoantibodies↗
PubMed1988

Deposition of terminal C5b-9 complement complexes on erythrocytes and leukocytes during cardiopulmonary bypass.

Hemolysis, leukopenia, a hemostatic deficit, and nonspecific systemic reactions collectively known as the postperfusion syndrome develop in patients who undergo cardiopulmonary bypass. We now report that terminal C5b-9 complement complexes are deposited on erythrocytes and polymorphonuclear neutrophilic leukocytes during cardiopulmonary bypass. Plasma samples taken from 48 unselected patients during and at the end of cardiopulmonary bypass contained raised levels of fluid-phase SC5b-9 complement complexes, indicating that the complement sequence had been activated to completion. Various degrees of overt intravascular hemolysis were observed in all the patients, and lysed erythrocyte membranes were recovered from the blood samples. Immunoassays performed with use of antibodies to C5b-9 neoantigens demonstrated the presence of C5b-9 on red-cell ghosts but not on intact erythrocytes. The appearance of ghosts carrying C5b-9 always coincided with hemolysis. Furthermore, granulocytes isolated from 20 patients during bypass were all found to carry C5b-9 complexes, whereas cells isolated before or 24 hours after surgery carried no C5b-9. The neoantigen-positive material present in detergent extracts of granulocytes sedimented in a broad peak (25 to 40 sedimentation coefficient [S]) in sucrose-density gradients, exactly as did pore-forming C5b-9 complexes. Deposition of C5b-9 on blood cells during cardiopulmonary bypass may be partly responsible for the hemolysis and may augment granulocyte activation by the stimulation of arachidonate metabolism in those cells.

Autoantibodies↗
PubMed1988

High-dose IgG for post-transfusion purpura-revisited.

Therapy for post-transfusion purpura (PTP) is controversial. We have evaluated the effect of high-dose IgG (HDIgG) in 11 PTP cases investigated in our institution and summarized the clinical data of 8 additional cases reported in the literature. Two of these 19 cases had to be eliminated from the analysis (1 patient received a total dose of less than 30 g of IgG; 1 patient died 2 days after starting HDIgG therapy from congestive heart failure). Out of a total of 17 cases, 16 had good or excellent response reaching normal platelet values within few days; only one failure was observed. Five patients relapsed, but attained complete remission after a second course (dose) of IgG. Total doses per course ranged between 52 and 180 g of IgG. Five different IgG preparations were used and seemed similarly effective. No adverse reactions were observed. We conclude that HDIgG is the treatment of choice for PTP.

Adult↗
PubMed1988

A new platelet-specific alloantigen Bra. Report of 4 cases with neonatal alloimmune thrombocytopenia.

Sera obtained from 4 mothers of children with neonatal alloimmune thrombocytopenia contained a platelet-specific alloantibody, anti-Bra, which defined an antigen apparently different from all known platelet alloantigens. All 4 fathers were Bra positive, whereas all mothers were Bra negative. The minimal postnatal values of platelet counts ranged from 19 X 10(9) to 75 X 10(9)/1. Family studies showed that the Bra antigen is inherited as an autosomal, codominant trait. Its antigen frequency in the German population is 20% (21 of 105 unrelated donors were positive). The estimated gene frequency is 0.11. The antibodies were identified by a glycoprotein-specific enzyme immunoassay using monoclonal antibodies for antigen immobilization, while they could not reliably be detected by binding assays employing whole platelets (platelet immunofluorescence, indirect competitive ELISA).

Adult↗
PubMed1987

Redistribution of platelet glycoproteins induced by allo- and autoantibodies.

The redistribution of platelet glycoproteins (GP) Ib, IIb and IIIa in response to stimulation with human platelet specific alloantibodies, autoantibodies and a quinidine-dependent antibody was investigated using immunofluorescence and a quantitative radioimmunoassay. The platelet GPs carrying the corresponding epitopes were determined using immunoblot technique or radioimmunoprecipitation. In accordance with previous results obtained with murine monoclonal platelet specific antibodies, redistribution upon stimulation with human platelet reactive antibodies was observed only due to reactions with epitopes on GP IIb, IIIa, respectively, but not on GP Ib. We therefore believe that membrane redistribution of human platelets induced by various antibodies is a function of the GP recognized by those antibodies rather than the source of the platelet reactive antibody.

Antibody Specificity↗