T-cell interactions with second generation glass-supported lipid bilayers

Thesis

T cells must efficiently scan and discriminate foreign antigen from self. Failure to do so leads to immunodeficiency or autoimmunity. How this process is achieved remains unclear, but recent developments have indicated the topology of the T-cell membrane, and nature of the contact interfaces formed with antigen presenting cells (APCs) may be key. Due to the difficulty of studying cellular contacts, in vitro systems that isolate and test specific elements of T cell-APC interface have been essential. One key example is glass-supported lipid bilayers (SLBs) functionalised with foreign antigen and the large adhesive protein ICAM-1 (referred to as ‘first generation’ SLBs). First generation SLBs have provided unparalleled insight into the spatiotemporal dynamics of key proteins at the T-cell membrane, however, to study the topology of initial membrane contacts, whereby antigen is first detected and discriminated, additional components must be considered. The work described in this thesis sought to establish a novel SLB that builds upon the strong foundation of first generation SLBs by additionally incorporating two key elements of the APC membrane: small adhesion molecules and the glycocalyx (referred to as ‘second generation’ SLBs). Using second generation SLBs, the results of this thesis addressed the competing effects of adhesion proteins, the glycocalyx, and different antigen density on T-cell contacts, signaling, and antigen discrimination. By visualising the T-cell membrane and exclusion of the glycocalyx on the SLB, small, dynamic membrane protrusions, referred to as microvilli, dominated the contact interface between T cell and SLB. T-cell signaling was rapidly initiated from few microvillar contacts even in the presence of very low densities of antigen, highlighting the sensitive and efficient nature of antigen detection. Finally, antigen discrimination was found critically dependent on the small and constrained geometry of microvillar contacts. In summary, second generation SLBs are a powerful approach to dissect the early events that govern T-cell activation.

Authors: Jenkins, EB

• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Microvilli; Antigen sensitivity; TIRF; Glycocalyx; Antigen discrimination; T-cell; glass-supported lipid bilayers; TCR; Adhesion proteins
• Subjects: T cells--Receptors