Jochen Hoch

Tr1 and naturally occurring regulatory T cells induce IgG4 in B cells through GITR/GITR‐L interaction, IL‐10 and TGF‐β

Regulatory T cells exert their function through the modulation of both T and B cell responses. Our previous studies demonstrated that IL‐10‐producing Treg (Tr1) can induce B cells to secrete IgG4 in a cell‐contact‐dependent manner. The benefit of such non‐inflammatory B‐cell responses is apparent in the hyporesponsive state of patients with helminth infections such as Onchocerciasis. Here, we investigated the mechanisms involved to induce IgG4, within B:Tr‐cell co‐cultures, using IL‐10‐producing tetanus‐toxoid‐specific regulatory T cell lines and clones (Tr‐TCC) from human PBMC. During the generation process, we found that increasing Foxp3 levels in regulatory T cell lines correlated with their ability to induce IgG4 in B cells. Using Tr‐TCC, we found that blocking glucocorticoid‐induced tumour necrosis factor receptor‐related protein (GITR) molecules selectively prevented IgG4 production as did neutralizing Ab to glucocorticoid‐induced tumour necrosis factor receptor‐related protein ligand (GITR‐L), IL‐10 and TGF‐β. Furthermore, the prevention of IgG4 induction by anti‐GITR Ab was reversed by excess rIL‐10 but not rTGF‐β. In contrast, anti‐ICOS and anti‐CTLA‐4 Abs had no effect. When compared with Tr‐TCC, freshly isolated CD4+CD25+ T cells, but not effector T cell populations, induced low levels of IgG4, which were also blocked by anti‐GITR and anti‐GITR‐L Ab. Thus, the mechanism of IgG4 induction by regulatory cells involves GITR–GITR‐L interactions, IL‐10 and TGF‐β.

Human Plasmacytoid Dendritic Cells Support Th17 Cell Effector Function in Response to TLR7 Ligation

Signals involved in the commitment of Th17 differentiation are of substantial interest for our understanding of antimicrobial defense mechanisms and autoimmune disorders. Various ways in which myeloid dendritic cells modulate Th17 differentiation have been identified. However, although plasmacytoid dendritic cells (PDCs) are regarded as important players in antiviral/antimicrobial host defense and autoimmune diseases, a putative modulatory role of PDCs in Th17 differentiation has not yet been elucidated in detail. We demonstrated that PDCs are capable of promoting Th17 differentiation in response to TLR7 stimulation. Further, both the differentiation of Th17 cells from naive T cells and the amplification of Th17 effector functions of memory T cells are promoted by PDCs after TLR7 activation. Our data are of strong clinical relevance because TLR7 activation in PDCs might represent one of the missing links between innate and adaptive immune mechanisms and contribute to the amplification of Th17-driven autoimmune disorders as well as viral host defense.

Maternal intravenous immunoglobulin treatment does not prevent intracranial haemorrhage in fetal alloimmune thrombocytopenia

SUMMARY. In fetal alloimmune thrombocytopenia (FAIT) the fetus is threatened by intracranial haemorrhage (ICH); therefore early diagnostic and therapeutic intervention is required. We followed the clinical course of a 30‐year‐old woman during her fifth pregnancy after she had given birth to a child with alloimmune thrombocytopenia due to anti‐Zwa. The fetus was monitored by 13 fetal blood samplings (FBS) always followed by transfusion of either maternal or compatible donor platelets. Intravenous immunoglobulin (ivIg) treatment of the mother was begun at 20 weeks of gestation when the fetal platelet count was 36 times 109/1. The fetal platelets were typed Zwa positive by DNA analysis. Despite 11 weeks of maternal ivIg treatment fetal platelet counts progressively declined to 6 times 10/1 and ICH occurred. Subsequently, the fetus was successfully managed by intrauterine platelet transfusions at shorter intervals (3–5 days) and elective Cesarean section was carried out at 35 weeks of gestation. We conclude that maternal ivIg treatment does not prevent ICH in FAIT. The treatment of choice for severely affected cases is serial FBS combined with transfusion of compatible platelets.

Therapy with intravenous immunoglobulin G (ivIgG) during pregnancy for fetal alloimmune (HPA-1a(Zwa)) thrombocytopenic purpura

We have evaluated the effect of maternal intravenous immunoglobulin G (ivIgG) treatment on platelet counts in fetal alloimmune thrombocytopenia. Seven patients were studied. All of them were multiparous women who had been immunized against the HPA‐1a antigen during previous pregnancies and had given birth to at least one severely thrombocytopenic infant. In this study, umbilical blood collection was performed first at the 20th week of gestation and repeated 2–13 times (mean 6 times), depending on the degree of fetal thrombocytopenia. Fetal platelet counting was combined with intrauterine transfusion of 20–30 ml of HPA‐1a‐negative platelet concentrates to prevent bleeding following umbilical cord puncture. Initial fetal platelet counts ranged from 10 000 to 91 000 per μl. Maternal treatment with ivIgG (1 g per kg body weight; mean dose 70 g) was given once a week over 7 weeks. In five of seven cases, the basal platelet count did not rise and in two of these cases, it decreased during maternal ivIgG treatment. In one fetus, the baseline platelet count increased from 10 000 to 35 000 per μl during ivIgG, and in another fetus from 23 000 to 64 000 per μl. Our observations suggest that ivIgG has no definite benefit for fetal alloimmune thrombocytopenia. Since platelet counts can be very low, careful fetal monitoring by umbilical blood sampling is required. Frequent platelet transfusions in short intervals may be necessary to increase platelet counts in extremely thrombocytopenic fetuses.

Development, validation and evaluation of a homogenous one-step reverse transcriptase-initiated PCR assay with competitive internal control for the detection of hepatitis C virus RNA

Abstract Nucleic acid amplification testing for hepatitis C virus (HCV) RNA has become an essential tool for the prevention and clinical management of hepatitis C. We describe the development, validation and evaluation of a homogenous reverse transcriptase-initiated HCV-PCR assay with competitive internal control that is applicable to both the quantitative detection of HCV genomes in single patient samples and the screening of blood donations by mini-pool testing. For the implementation of a positive run control, a HCV RNA-positive plasma sample was calibrated against an international HCV RNA standard preparation. For quantification purposes, an in vitro-transcribed RNA calibrator sequence was used. The detection limit of the assay (95% positive cut-off) was determined by probit analysis and was calculated as 114IU/mL. Comparable sensitivity to different HCV template sequences was verified for HCV genotypes 1–5. Quantitative test results correlated well with viral loads that had been previously determined by the Bayer VERSANT HCV RNA 3.0 bDNA assay (n=53, R=0.943, p<0.001). During more than 5years of blood donation testing, the specificity of the assay was found to be 99.51%. All assay components showed constant performance during this time period. In conclusion, we introduce a well-proven method that allows fast and reliable quantification of HCV genomes.

A new platelet alloantigen, Swia, located on glycoprotein Ia identified in a family with fetal and neonatal alloimmune thrombocytopenia

BACKGROUND: Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a bleeding disorder caused by transplacental passage of maternal antibodies to fetuses whose platelets (PLTs) express the corresponding human PLT antigen (HPA).

Maternal and fetal hepatitis C virus exposure by intrauterine transfusion

We report a case of accidental exposure to hepatitis C virus by an intrauterine transfusion that resulted in infection of the mother but not the child.

Antikörperinduktion nach intrauterinen Eingriffen

In einer retrospektiven Analyse wurden immunhamatologische und klinische Daten der letzten 2 Jahre von 48 Patientinnen, deren Feten wegen einer Erythroblastose intrauterin transfundiert wurden, reeval