A spectrum of biophysical interaction modes between T cells and different antigen-presenting cells during priming in 3-D collagen and in vivo

Abstract

IntroductionFor activation, T cells must physically engage antigen-presenting cells (APCs). 1 With B cells as APCs, the interaction plane, termed "immunologic synapse," 2 is a highly organized structure of signaling and adhesion molecules. 3 A mature synapse requires at least 30 minutes of stable cell-cell interaction to form 2 and can last for several hours in vitro 4 and in explanted lymph nodes. 5 Although investigated mostly with B cells or surrogate APCs in liquid cultures, the concept of long-term contacts has previously been considered a universal feature of all cognate T cell-APC (T-APC) interactions. 6 However, in promigratory collagen matrices as environment for T-APC interaction also dynamic and short-lived encounters to dendritic cells (DCs) are able to induce the full spectrum of T-cell signaling and activation. 7 Here, T cells engage DCs only for a few minutes, detach, and establish new contacts to neighboring DCs until activation is achieved. 8 Migrating T cells can drag a mature synapse over the surface of an APC, showing the principal compatibility of T-cell migration and synapse maintenance. 9 Furthermore, studies on APC-T interactions in explanted lymph nodes 10 or thymic organ cultures 11 have observed both static and dynamic interactions between T cells or thymocytes and local APCs. Intravital imaging revealed a 3-phase model of T-APC interaction in a lymph node, in which CD8 T cells displayed a period of 8 hours, characterized by short-lived and dynamic DC scanning, followed by 12 hours with stable interactions to single DCs and a return to high motility afterward. 12 During adhesive contacts, T cells maintained considerable cytoskeletal activity and shape change. 12 Weaver's group (Hurez et al 13 and Saparov et al 14 ) described a heterogeneity in naive T cells, leading to a majority of short-interacting cells, which could proliferate but did not produce interleukin 2 (IL-2), the latter only being produced by T cells making long contacts to APCs. T-cell receptor (TCR)-proximal signals such as phosphorylation of zeta-associated protein 70 (ZAP-70) or Lck 15 are only detectable for the first 15 minutes after the onset of a contact and are already absent before a synapse has fully matured. 16 In contrast, active phosphatidyl inositol 3 (PI3)-kinase is located in an initial segment (IS) over the entire period of T-APC interaction and interference with this process inhibits T-cell activation. 17,18 However, besides a continuous TCR signal, also discontinuous signaling can lead to T-cell activation and effector function. 19 Together, these observations suggest that a spectrum of interaction modes, reaching from static adhesion and clustering to dynamic migratory encounters with APCs, can lead to the activation of T cells. 8,20 So far no systematic analysis on the biophysical and molecular principles underlying static versus dynamic interactions has been performed. According to one hypothesis, the nature of the APC, which is encountered by the T cell, is decisive for the mode of interaction, 8 wh...

3D and 4D imaging of immune cells in vitro and in vivo

“…The direct observation also allows to investigate cell-cell interactions that is especially important when analyzing the function of immune cells (Gunzer 2007). For example, the duration of contacts between T cells and APC (Bousso and Robey 2003;Castellino et al 2006;Gunzer et al 2000Gunzer et al , 2004Mempel et al 2004;Miller et al 2004a;Shakhar et al 2005), cytotoxic cells and their targets (Mempel et al 2006;Stinchcombe et al 2001) or B cells with antigen containing cells have been analyzed (Batista et al 2001;Fleire et al 2006). …”

“…These are easily generated and transparent and thus allow the use of high resolution microscopy for the imaging of cells Reichardt et al 2007). The use of Xuorescent indicators of cell physiology, such as Calcium-sensitive dyes is also possible allowing the high-resolution imaging of cell signaling (Gunzer et al 2000(Gunzer et al , 2004Waibler et al 2008). …”

“…It was only by the beginning of 2000 that the use of 2PM for addressing immunological questions was proposed (Dustin et al 2001). Shortly after this, the Wrst papers investigating cell migration in explanted lymph nodes or thymic stromal reaggregate cultures (Bousso et al 2002) were published, followed by true intravital studies (Gunzer et al 2004;Mempel et al 2004). Meanwhile the number of reports using intravital 2PM for immunological questions has risen enormously, spanning from the cellular events of T cell activation (Miller et al 2004a), formation and function of germinal centers (Allen et al 2007b;Schwickert et al 2007) or function of regulatory T cells (Tadokoro et al 2006) to complex processes such as granuloma formation ) and the delivery of antigens (Carrasco and Batista.…”

“…The method of supply can vary. Experimental animals are either supplied with a 1-2% concentration of IF in O 2 /air by an inhalation mask (Qi et al 2006) or the animals are intubated and get a similar mixture of the anesthetic by mechanical ventilation (Gunzer et al 2004;Niesner et al 2007). In our hands, the latter approach is the most suitable method for long-term imaging experiments, since it allows a very precise and tunable application of narcosis.…”

The Biophysics of T Lymphocyte Activation In Vitro and In Vivo

“…Immigrant T cells will start scanning the surrounding APCs for a peptide/MHC complex capable of binding with high affinity to their TCR. By doing this, they display an interesting and diverse spectrum of biophysical interactions with each of these types of APC [28,34], which will be looked at in detail below. If the search is finally successful, the T cell will respond to the new situation with proliferation and differentiation into a primed effector cell.…”