Subcellular dynamics of T cell immunological synapses and kinapses in lymph nodes

Abstract

In vitro studies have revealed that T cell activation occurs during the formation of either dynamic or stable interactions with antigenpresenting cells (APC), and the respective cell junctions have been referred to as immunological kinapses and synapses. However, the relevance and molecular dynamics of kinapses and synapses remain to be established in vivo. Using two-photon imaging, we tracked the distribution of LAT-EGFP molecules during antigen recognition by activated CD4 + T cells in lymph nodes. At steady state, LAT-EGFP molecules were preferentially found at the uropod of rapidly migrating T cells. In contrast to naïve T cells that fully stopped upon systemic antigen delivery, recently activated T cells decelerated and formed kinapses, characterized by continuous extension of membrane protrusions and by the absence of persistent LAT-EGFP clustering. On the other hand, activated CD4 + T cells formed stable immunological synapses with antigen-loaded B cells and displayed sustained accumulation of LAT-EGFP fluorescence at the contact zone. Our results show that the state of T cell activation and the type of APC largely influence T cell-APC contact dynamics in lymph nodes. Furthermore, we provide a dynamic look at immunological kinapses and synapses in lymph nodes and suggest the existence of distinct patterns of LAT redistribution during antigen recognition. Reorganization of the actin cytoskeleton (2, 3), translocation of the microtubule organizing center (4, 5), segregation of surface and signaling molecules into central and peripheral regions of the contact zone (cSMAC and pSMAC, respectively) (6, 7), condensation of membrane microdomains (8), and formation of dynamic microclusters (9-13) contribute to immunological synapse formation and have been proposed to participate in and/or regulate T cell activation. Of note, the topology of the immunological synapse is not unique and may depend on the type of APC, the T cell phenotype, and the strength of stimulation (14-16). In various experimental conditions, both bull's eye shaped and multifocal synapses have been described (6,7,17,18).In sharp contrast, evidence for organized immunological synapse and cSMAC formation in vivo is scarce and has been limited to static images (19)(20)(21)(22)(23). This remains a critical issue because T cell and APC behaviors are profoundly dependent on their surrounding microenvironment. For instance, T cells are highly motile in secondary lymphoid organs (24) but largely sessile in cell suspension. Thus, the topology and dynamics of T cell synapses in vivo remain to be established (25).Two-photon imaging is a technique of choice to tackle immune cell behavior in physiologic settings (26). Several studies have characterized the frequency, stability, and duration of interactions established by T cells and dendritic cells (DCs) or B cells in intact lymph nodes (reviewed in refs. 27 and 28). One of the interesting observations offered by these studies is that antigen (Ag) recognition by T cells can occur during long-lived interactio...

The Wiskott-Aldrich syndrome protein permits assembly of a focused immunological synapse enabling sustained T-cell receptor signaling

“…This hypothesis is supported by the finding that recently activated T cells forming kinapses in vivo engage their TCR efficiently but fail to accumulate the signaling molecule LAT at the IS and emit only short calcium spikes. 29 Since an initial wave of [Ca 2+ ]i is required for the stop signal 30 and since the [Ca 2+ ]i signaling pattern regulates the shape and stability of T cells contacting APC, 31 it may be argued that a primary defect in calcium mobilization is responsible for the phenotype of WAS T cells. However, ]i strongly indicates that the abnormal calcium mobilization pattern is a consequence rather than a cause of the disorganized WAS T-cell IS.…”

Signal strength regulates antigen-mediated T-cell deceleration by distinct mechanisms to promote local exploration or arrest

“…GFP + OT-I CD8 + T cells were preactivated in vitro for 72 h using anti-CD3/CD28 beads (Dynal) in the presence of 25 U/mL recombinant IL-2 (Roche) and allowed to migrate in 6-μm-wide microchannels coated with pMHC (11). In some experiments, T cells were retrovirally transduced to express GFP-centrin or LAT-GFP (26,27) and stained with 1 μg/mL Hoechst 33342 (Life Technologies). In brief, OT-I T cells were activated for 2 d with anti-CD3/CD28 beads (Dynal) in the presence of 25 U/mL recombinant IL-2 (Roche) and spin-transduced at day 2 and day 3 after activation as previously described (27).…”

“…In some experiments, T cells were retrovirally transduced to express GFP-centrin or LAT-GFP (26,27) and stained with 1 μg/mL Hoechst 33342 (Life Technologies). In brief, OT-I T cells were activated for 2 d with anti-CD3/CD28 beads (Dynal) in the presence of 25 U/mL recombinant IL-2 (Roche) and spin-transduced at day 2 and day 3 after activation as previously described (27). When indicated, EGTA (2.5 mM; Sigma), CK666 (25 μM; Tocris), or PP2 (20 μM; Calbiochem) was added to the culture medium during the migration assay.…”

Real-time analysis of T cell receptors in naive cells in vitro and in vivo reveals flexibility in synapse and signaling dynamics

“…The only dynamic molecular imaging in the LN to date has shown that LAT (linker of activated T cells) localizes to the contact interface during stable interactions of activated T cells with antigen-bearing B cells but not during motile interactions of activated T cells with DCs (Azar et al, 2010). Static imaging of CD43-GFP fusion proteins also demonstrated T cell-DC interactions that exclude CD43 from the contact interface (Stoll et al, 2002), which is consistent with this molecule's position in synapses formed in vitro.…”