Gertrud Mueller-Eckhardt

348 cases of suspected neonatal alloimmune thrombocytopenia

pump to allow pulsatile tocolytic infusion, hoping to reduce the total dose and thus the side effects. In 33 patients pulsatile bolus tocolysis was compared with continuous tocolysis in a control group of 38 patients. Bolus tocolysis required considerably less beta-sympathomimetic agent for comparable therapeutic success (median dosage 3.0 versus 15.9 mg, P < 0.001). Duration of therapy under bolus tocolysis was also significantly shorter (P < 0.05). Birth weight was higher after bolus tocolysis (median 3,070 versus 2,580 gm, P = 0.05). Additional indicators favored bolus tocolysis but were not statistically significant: a longer gestational period, fewer infants weighing < 2500 gm, and a lower incidence of respiratory distress syndrome. Pulmonary edema occurred in one patient during continuous tocolysis.

Detection of platelet autoantibodies by a radioactive anti-immunoglobulin test.

Abstract. A direct and an indirect version of a platelet radioactive anti‐immunoglobulin test (PRAT) has been developed. It is shown that this assay is sensitive, reproducible and quantitative for the demonstration of HLA as well as incomplete P1A1 antibodies. Furthermore, platelet autoantibodies were searched for in sera of 105 thrombocytopenic patients. Positive results were obtained in 15 out of 45 patients with chronic idiopathic thrombocytopenic purpura (ITP), in 1 of 17 cases with acute ITP and in 3 of 4 patients with ITP‐like syndrome of systemic lupus erythematosus (SLE). The platelet autoantibodies mostly had low titers, reacted with autologous platelets and did not show any specificity. An elevated concentration of IgG on autologous platelets was detected by the direct PRAT in 11 of 18 patients with ITP and in 4 of 5 patients with thrombocytopenia and suspected SLE. 4 of the 7 negative ITP cases were in clinical remission or had platelet counts of over 50,000/μl. There appeared to be an inverse correlation between the concentration of surface‐bound IgG and the platelet number in patients with ITP and SLE. It is concluded that the PRAT is a new and valuable tool for the detection of various types of platelet antibodies and therefore a true alternative to existing serological techniques in platelet immunology.

HLA‐DRw6, a New Immune Response Marker for Immunization against the Platelet Alloantigen Bra

We have recently detected a new platelet alloantigen, Br a , which also belongs to a diallelic system (Br a /Br b ) and resides on glycoprotein Ia. Maternal immunization against the Br a antigen of the fetus is the second most frequent cause of neonatal alloimmune thrombocytopenia in the German population. We here report a strong association of Br a immunization with the presence of HLA-DRw6

Islet cell antibodies and the development of diabetes mellitus in relation to mumps infection and mumps vaccination.

SummaryIslet cell antibodies were investigated in 127 non-diabetic children after mumps infection and in four out of seven children who developed diabetes mellitus shortly after active mumps vaccination. Twenty-one of the children who had mumps and all four vaccinated children who were tested had islet cell cytoplasmic antibodies. In contrast, islet cell surface antibodies were detected in 43 out of 68 patients with mumps infection and in 32 out of 44 patients with other viral diseases. All but one mumps-infected child and all the other viral infected patients investigated did not develop diabetes mellitus. The mumps-infected ICA positive children did not show those HLA-frequencies associated with Type 1 diabetes.

Immunogenetic and serological investigations in nonpregnant and in pregnant women with a history of recurrent spontaneous abortions

In the context of a controlled multicenter study on intravenous immunoglobulin (IVIG) treatment of patients with a history of unexplained recurrent spontaneous abortions (RSA), a number of controversial immunological parameters were evaluated prior to and during pregnancy with respect to their diagnostic and/or prognostic significance. A total of 390 serum samples from 52 patients were investigated. Sharing of 2 or more HLA (A, B, DR, DQ) antigens was significantly more frequent in RSA couples than in controls. The rate of cytotoxic or Fc-receptor (FcR)-blocking antibodies was not significantly lower in RSA patients than in individuals with normal pregnancies. Both tumor necrosis factor-alpha (TNF-alpha) levels and IgG anticardiolipin antibodies (IgG-ACA) were significantly increased in the patient group. While the occurrence of HLA sharing, cytotoxic/FcR-blocking antibodies and IgG-ACA did not correlate with the outcome of pregnancy, TNF-alpha levels were found to be significantly higher in patients with subsequent miscarriage than in those with successful pregnancy. IgG-ACA, if present, significantly decreased during the course of successful pregnancy but remained high in patients with subsequent abortion. It is concluded that the diagnostic and/or prognostic value of HLA sharing and cytotoxic/FcR-blocking antibodies has been overestimated while TNF-alpha and ACA levels are potential diagnostic markers and/or exhibit prognostic significance in subgroups of RSA patients.

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.

Post-transfusion thrombocytopenic purpura: Immunological and clinical studies in two cases and review of the literature

ZusammenfassungEs werden die ersten beiden Patienten mit posttransfusioneller thrombozytopenischer Purpura beschrieben, die in Österreich und in Deutschland diagnostiziert werden konnten. Beide Patienten waren Frauen im Alter von 51 und 60 Jahren. Die Purpura wurde durch Bluttransfusionen ausgelöst mit einer Latenzzeit von zwei bzw. sieben Tagen. Die thrombozytopenische Phase dauerte 22 bzw. länger als 60 Tage. In einem Fall bestand neben der Thrombozytopenie eine Agranulozytose infolge einer vorübergehenden Knochenmarksinsuffizienz. Beide Patienten waren negativ für das thrombozytenspezifische Antigen PlA1 (= Zwa). Ihr Serum enthielt sowohl PlA1- als auch starke HLA-Antikörper. Die klinischen und serologischen Befunde beider Patienten werden eingehend dargestellt. Eine Literaturübersicht mit bisher 25 beschriebenen Fällen ist angefügt.SummaryTwo patients with post-transfusion thrombocytopenic purpura are described, the first cases recognized in Austria and Germany. Both patients were female, 51 and 60 years of age. The purpura was evoked by blood transfusions with a latent period of 2 and 7 days. The thrombocytopenic episode lasted for 22 and over 60 days. In one case, thrombocytopenia was associated with agranulocytosis due to transient bone marrow failure. Both patients were negative for the platelet-specific antigen PlA1 (= Zwa). Their sera contained PlA1 as well as potent HLA antibodies. Detailed clinical and serological data are presented. The literature with a total of 25 cases so far reported is surveyed.

HLA antigens on platelet membranes. In vitro and in vivo studies.

Abstract. In order to determine whether HLA‐A,B antigens of platelets are integral membrane constituents or rather represent adsorbed plasma proteins, their presence in plasma and their adsorbability onto platelet membranes was studied by in vitro and in vivo experiments. The amount of HLA antigens was quantitated by inhibition of lymphocytotoxicity (LCT) and by enzyme‐linked immunosorbent assay (ELISA) using operationally monospecific polyclonal HLA antibodies or murine HLA‐specific monoclonal antibodies, respectively. We found that in 11 out of 13 HLA‐A2 and in 9 out of 10 HLA‐B13 experiments, platelets from antigen‐negative donors pretreated with plasma from the same number of antigen‐positive donors inhibited LCT to the same extent as platelets from antigen‐positive donors. Nevertheless, the in vitro adsorbed HLA antigens onto antigen‐negative platelets were, unlike those on antigen‐positive platelets or in plasma, not reactive with monoclonal antibodies as quantitated by ELISA. Similarly, infusion of HLA‐A2‐negative platelets from single donors into 3 HLA‐A2‐positive, thrombocytopenic patients with bone marrow failure led to a good platelet increment, but did not convert the HLA type of donor platelets, neither at 2 h nor at 18 h posttransfusion. On the basis of these results, we conclude that soluble HLA antigens can be taken up by human platelets from plasma in small amounts. However, the major portion of HLA antigens appears to be integral membrane constituents.

Autoimmunization against the neutrophil-specific NA1 antigen is associated with HLA-DR2

A significant association of autoimmune neutropenia (AIN) in infants due to NA1-specific autoantibodies and HLA-DR2 is reported. Nineteen of 26 infants presenting with AIN and NA1 autoantibodies possessed the DR2 antigen, while only one out of six children with AIN, but non-NA1-specific autoantibodies, was DR2 positive. Furthermore, one adult patient with primary biliary cirrhosis and periods of neutropenia due to NA1 autoantibodies also carried the DR2 antigen. All DR2-negative patients were positive for DRw6. These findings indicate that a close relationship exists between autoimmunization against the NA1 antigen and HLA-DR2 and possibly also DRw6.

The clinical significance of HLA antigens on red cells. Survival studies in HLA-sensitized individuals

To investigate the clinical significance of HLA determinants expressed on red cells (RBCs), 51Cr survival studies were carried out in six women (four healthy individuals, two patients with solid carcinoma) immunized against HLA antigens by pregnancy or blood transfusions, respectively. Donors were selected who were compatible in typical RBC antigen systems assayed by conventional techniques but were mismatched for the HLA antigens in question. Crossmatches also were performed with RBC, as well as with lymphocytes, by means of a radioimmune anti‐IgG test (RIAT). We found that RBC survival was shortened in all cases. The mean life‐span of RBCs depended on antigen specificity rather than on the antibody strength. HLA incompatibility of RBCs could be monitored by the RIAT in all donor/recipient pairs. We conclude that a shortened mean life‐span of RBC is to be expected by HLA antibodies, especially when HLA‐B7 is involved, but the severity of an in vivo immune reaction in HLA incompatible transfusions cannot be predicted from the in vitro tests used.