Faculty Bibliography

Dendritic cells (DCs) are myeloid lineage cells that are imprinted by their environment and that mature in response to microbial products. A crucial role of the DC is to impart this context-specific information to T cells as well as to present self and foreign MHC-peptide complexes through formation of an immunological synapse. The structure of the T cell-DC immunological synapse departs from the canonical structure formed with B cells or with supported planar bilayers in that it has multiple foci of T-cell receptor interactions rather than a central focus. Recent studies on model systems provide insight into the mechanisms and biological consequences of the unique T cell-DC synaptic patterns

Dendritic cells (DCs) interface innate and adaptive immunity in nonlymphoid organs; however, the exact distribution and types of DC within the kidney are not known. We utilized CX3CR1GFP/+ mice to characterize the anatomy and phenotype of tissue-resident CX3CR1+ DCs within normal kidney. Laser-scanning confocal microscopy revealed an extensive, contiguous network of stellate-shaped CX3CR1+ DCs throughout the interstitial and mesangial spaces of the entire kidney. Intravital microscopy of the superficial cortex showed stationary interstitial CX3CR1+ DCs that continually probe the surrounding tissue environment through dendrite extensions. Flow cytometry of renal CX3CR1+ DCs showed significant coexpression of CD11c and F4/80, high major histocompatibility complex class II and FcR expression, and immature costimulatory but competent phagocytic ability indicative of tissue-resident, immature DCs ready to respond to environment cues. Thus, within the renal parenchyma, there exists little immunological privilege from the surveillance provided by renal CX3CR1+ DCs, a major constituent of the heterogeneous mononuclear phagocyte system populating normal kidney

We have monitored active movements of the cell circumference on specifically coated substrates for a variety of cells including mouse embryonic fibroblasts and T cells, as well as wing disk cells from fruit flies. Despite having different functions and being from multiple phyla, these cell types share a common spatiotemporal pattern in their normal membrane velocity; we show that protrusion and retraction events are organized in lateral waves along the cell membrane. These wave patterns indicate both spatial and temporal long-range periodic correlations of the actomyosin gel

Both innate and adaptive immunity are dependent on the migratory capacity of myeloid and lymphoid cells. Effector cells of the innate immune system rapidly enter infected tissues, whereas sentinel dendritic cells in these sites mobilize and transit to lymph nodes. In these and other secondary lymphoid tissues, interactions among various cell types promote adaptive humoral and cell-mediated immune responses. Recent advances in light microscopy have allowed direct visualization of these events in living animals and tissue explants, which allows a new appreciation of the dynamics of immune-cell behaviour. In this article, we review the basic techniques and the tools used for in situ imaging, as well as the limitations and potential artefacts of these methods

T cell receptor (TCR) signaling is initiated and sustained in microclusters; however, it's not known whether signaling also occurs in the TCR-rich central supramolecular activation cluster (cSMAC). We showed that the cSMAC formed by fusion of microclusters contained more CD45 than microclusters and is a site enriched in lysobisphosphatidic acid, a lipid involved in sorting ubiquitinated membrane proteins for degradation. Calcium signaling via TCR was blocked within 2 min by anti-MHCp treatment and 1 min by latrunculin-A treatment. TCR-MHCp interactions in the cSMAC survived these perturbations for 10 min and hence were not sufficient to sustain signaling. TCR microclusters were also resistant to disruption by anti-MHCp and latrunculin-A treatments. We propose that TCR signaling is sustained by stabilized microclusters and is terminated in the cSMAC, a structure from which TCR are sorted for degradation. Our studies reveal a role for F-actin in TCR signaling beyond microcluster formation

Regulatory T (T reg) cells exert powerful down-modulatory effects on immune responses, but it is not known how they act in vivo. Using intravital two-photon laser scanning microscopy we determined that, in the absence of T reg cells, the locomotion of autoantigen-specific T cells inside lymph nodes is decreased, and the contacts between T cells and antigen-loaded dendritic cells (DCs) are of longer duration. Thus, T reg cells can exert an early effect on immune responses by attenuating the establishment of stable contacts during priming of naive T cells by DCs