Friedrich-Alexander-University of Erla ngen-Nuremberg, Ge rmanyFakultät für BiologieRegulation of B cell receptor signaling by CD22 and its ligand alpha-2, 6 Sialic acidDen Naturwissenschaftlichen FakultätenDer Friedrich-Alexander-Universität Erlangen –Nürnbergzur Erlangung des Doktorgradesvorgelegt von Snigdha GhoshausGhaziabad, IndiaRegulation of B cell receptor signaling by CD2 2 and its ligand alpha-2 , 6 Sialic acidDen Naturwissenschaftlichen FakultätenDer Friedrich- Alexander-Universität Erlangen –Nürnbergzur Erlangung des Doktorgradesvorgelegt von Snigdha GhoshausGhaziabad, IndiaAls Dissertation genehmigt von den Naturwissen-schaftlichen Fakultäten der Universität Erlangen-NürnbergTag der mündlichen Prüfung: 19.01.07Vorsitzender derPromotionskommission: Prof. Dr.Eberhard Bänsch Erstberichterstatter: Prof. Dr. Lars NitschkeZweitberichterstatter: Prof. Dr. Andre GessnerDeclaration I hereby declare that the submitted dissertation was completed by myself and none other, and I have not used any sources or materials other than those indicated. Moreover, I declare this dissertation has not been submitted elsewhere in this form and has not been used for obtaining any other equivalent qualification in any other organization. Additionally, other than this degree I have not applied or will not attempt to apply for any other degree, title or qualification in relation to this work. Erlangen, 14.10.06 Snigdha G hosh 1 INTRODUCTION.........