04.10.2007 13:24 3kJ Plasma Focus System 4 PhD Thesis.
X-Rays Emitted from the Plasma Focus,” Ph.D.
The aims of this study have been focused on the identification of cell surface structures involved in induction and regulation of apoptosis. Monoclonal antibodies against the major histocompatibility complex class I (MHC-I) were shown to induce apoptosis when cross-linked on the cell surface of different malignant cells having a pre-B or a myeloid precursor phenotype. The apoptotic response was not epitope dependent, since several different anti-MHC-I antibodies, reacting with different monomorphic determinants of the a chain or b2-microglobulin all induced apoptosis in these cells. However, external cross-linking of antibodies was strictly required for the apoptotic effect. Among cells originating from mature peripheral blood lymphocytes, anti-CD40 stimulated B-cells were susceptible to anti-MHC-I induced apoptosis, whereas resting as well as superantigen activated B- and T- cells were non-responsive to MHC-I ligation. The apoptotic process was not linked to protein kinase C activation or changes in cytoplasmic calcium concentration. In situ terminal doxynucleotidyl transferase staining of apoptotic cells at various stages during MHC-I induced cell death revealed that apoptosis occurred predominantly in the G2/M phase of the cell cycle, with the first apoptotic cells appearing after approximately 12 hours of incubation. The results suggest a role for MHC-I mediated apoptosis during differentiation and activation of certain hematopoietic cells.
THESES - Universal Plasma Focus Laboratory Facility
Molecular recognition is fundamental for the function of biological systems. The properties of the participating biomolecules dictate the type of forces, the strength and the dynamics involved in the interaction. Many interactions are very strong whereas others exhibit weak affinity. Typically, weak interactions work in concert to trigger a biological response. The advantage with this approach is the inherent dynamics. It has been shown that this approach can be successful for in vitro applications as well. By exposing analytes to a multitude of specific, weak affinity interactions, which are governed by fast association and dissociation rates, separation based on small differences in affinity is possible. The same principles can also be used to characterize biological weak affinity binders and for analytical purposes. This thesis has discussed biomolecular interactions in the weak affinity range (defined in this investigation as dissociation constants (KD) larger than 10 mM) in general and has focused on how they can be studied and exploited in vitro. Weak affinity monoclonal antibodies were used as model systems in three different applications: (i) to explore how weak affinity chromatography based on monoclonal IgM can be employed to separate structurally related steroids under non-denaturing conditions. (ii) to investigate the possibilities of studying weak interactions between antibodies and haptens with an optical biosensor based on surface plasmon resonance. A rationale for the design of such experiments to avoid inaccurate results was suggested. (iii) to introduce continuous real-time immunosensing for monitoring fluctuating concentrations of biomolecules in a flow.