Abstract Dendritic cells (DCs) are essential for uptake and presentation of antigens (Ags) for T cell activation and can be divided into subsets with varying Ag-presentation capacities. It is not clear whether intrinsic differences or variation in spatial localization and preferential Ag access both contribute to differential Ag-presentation by DC subsets. We thus developed a novel approach of combining multi-parameter (6 or 7 color) confocal microscopy with analytical masking to allow direct in-situ visualization of cellular populations identified by complex phenotypic surface markers. We determined the spatial localization of major resident lymph node (LN) DC subsets and observed preferential positioning of certain populations to distinct LN zones. Some DCs physically associated with lymphatic sinuses (LS) and extended dendrites directly into the LS. While small protein Ags can be directly delivered to resident DCs via LN conduits, particulate Ags are thought to be presented via migratory DCs arriving from peripheral sites. Using 2-photon microscopy, we observed the LS-associated DCs actively sampling the LS for particulate Ags and the formation of T cell clusters in zones proximal to the LS after particulate Ag injection. These results suggest the existence of specialized micro-domains for DC subsets within LN and suggest that LS-associated DC are important for T cell activation to particulate Ags. This research was supported by the Intramural Research Program of the NIH, NIAID.