Whitby, Helen Elizabeth; (2001) The role of glycosylphosphatidylinositol phospholipase D (GPI-PLD) in type one hypersensitivity. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

GPI-anchored proteins are a diverse group of molecules, which are ubiquitous in nature. The core structure of the GPI-anchor is highly conserved across a number of different species, a feature that implies a biological significance. Glycosylphosphatidylinositol-phospholipase D (GPI-PLD) is a 115 kDa glycoprotein which is found in high concentrations in mammalian serum. GPI-PLD hydrolyses GPI anchors, and it has been suggested that the enzyme is involved in the selective release of GPI-anchored proteins from the cell surface. GPI-PLD and GPI-anchored proteins have been implicated in a number of pathological situations, including T cell activation, insulin-mediated signalling and parasite immune evasion That GPI-PLD might play a role in the IgE-dependent activation of mast cells was suggested following experiments using a polyclonal antibody against bovine GPI-PLD. Inclusion of this antibody in experiments to activate mast cells lead to inhibition of the cells activation. However, this research was never completed. The research undertaken in this thesis has employed the Rat Basophilic Leukaemia cell line (RBL-2H3) as an analogue of Type One Hypersensitivity. IgE-dependent and independent stimulation of the cells was achieved, after which time the cells were employed in a variety of experiments to determine the role of GPI-PLD in their activation. Techniques were used to determine whether the cells generated the enzyme, It was determined that the cells did not generate mRNA, but contained the protein. The source of the enzyme was the Foetal Bovine Serum in the culture medium, and techniques were employed to inactivate or remove the enzyme from the serum. The effect on the cells behaviour was ascertained. Conclusions drawn were that RBL-2H3 cells employ a serum component, with characteristics of a GPI-PLD enzyme, in IgE-mediated activation.

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