In vivo and in vitro evolution of molecular mechanisms - Importance in B cell development and phage display

Sammanfattning: Bone marrow resident hematopoietic stem cells differentiate into all different types of lymphoid populations, there among mature naive B cells expressing IgM and IgD. During the maturation, the B cells are subjected to several steps of selection to ensure proper development of the antigen receptor. The mechanisms regulating the selection are to great extent unknown. In paper I of this thesis, we demonstrate the presence of the Fas system in late stages of B lymphopoiesis and further discuss the implication of these findings. In paper II, we investigated the molecular events accompanying the apoptotic process observed in pre-B cells following cross-linking of MHC class I. We were able to show that the apoptotic process was not linked to activation of protein kinase C nor to changes in cytosolic Ca2+ concentrations, intracellular events common in cells undergoing apoptosis. We utilised the differential display technology to detect two genes important in MHC class I mediated apoptosis. The objective in paper III was to functionally dissect the protein responsible for the infection of bacterial cells by filamentous bacteriophage i.e. the adsorption protein. The improved understanding of the mechanisms behind the infection process could be utilised in the construction of phage display systems used for improved protein expression, as in paper IV, or for studying protein – protein interactions, as in paper V.