Untersuchung genetisch modifizierter Mäuse bezüglich IgE vermittelter allergischer Reaktionen, T-Zellentwicklung und der Abwehr endogener Retroviren

The current study consists of four different projects: the study of active systemic anaphylaxis (ASA) in IgE knock-in mice, the generation of transgenic knock-in mice overexpressing human IgE, the generation of mice with an inducible knock-out of PLCγ1 and the relevance of TLR3, TLR7 and TLR9 in controlling endogenous retroviruses (ERV) and ERV induced tumours. In the first project IgE knock-in mice were analysed. In these mice the regulatory mechanism of IgG1 was transferred to IgE. As a result they show a strong overexpression of IgE in vivo and in vitro during a normal B and T cell development. In vitro analyses confirmed the expression of membrane bound IgE on the surface of their B-cells. Furthermore twice as much IgE bound to FcεRI could be detected in IgE knock-in mice than in their wild type littermates. In mice immunized with the model antigen TNP-OVA an extreme increase of antigen specific IgE was shown. By injecting mice with TNP-OVA an ASA was triggered, that was much stronger in IgE knock-in mice than in the controls. Therefore it could be determined that an ASA in IgE knock-in mice is mediated by IgE and not by IgG1. Moreover the depletion of basophils by Ba103 antibodies showed that an IgE mediated ASA is activated predominantly by basophils and less by mast cells when there is a high specific IgE level. The second project was the generation of knock-in mice with a strong overexpression of human IgE. The new model should add to a better understanding of IgE mediated reactions in humans. In the third project a mouse with an inducible knock-out of the phospholipase-Cγ1 (PLCγ1) should be generated. Therefore two loxP sites were inserted in the gene of PLCγ1. It is possible to genered tissue specific PLCγ1-iko mice from such floxed mice by a deletion of the loxP flanked exons. In this way it is possible to generate mice e.g. with a knock-out only in T cells to analyse the importance of PLCγ1 in T cell development especially in regulatory T cells. The appropriate targeting vectors and embryonal stem cells could be generated successfully. But after the injection into blastocystes no germ line transmission occured despite a hight chimerity of the offspring. In the last part of this study the importance of the endosomal nucleic acid recognizing toll like receptors 3, 7 and 9 for controlling endogenous retroviruses and tumours they induce was analysed by use of corresponding knock-out mice. Thereby a spontaneous uncontrolled viremia of the murine leukemia virus (MuLV) in TLR7 deficient mice was detected. But only TLR3, TLR7 and TLR9 triple deficient animals developed virus induced pre-T-cell acute lymphoblastic lymphomas (T-ALL). The insertion of the MuLV provirus into the oncogenes Nup214 and Notch-1 leads to a deregulation of the corresponding proteins, which could contribute to the development of T-ALL. Additionally an increased autoimmune reaction in TLR379-/- mice could be shown.