Mouse lymphoid tissue contains distinct subsets of langerin/CD207 dendritic cells, only one of which represents epidermal-derived Langerhans cells.

Langerin/CD207 is a C-type lectin associated with formation of Birbeck granules (BG) in Langerhans cells (LC). Here, we describe a monoclonal antibody (mAb 205C1) recognizing the extracellular domain of mouse langerin. Cell-surface langerin was detected in all epidermal LC, which presented a uniform phenotype. Two subpopulations of langerin+ cells were identified in peripheral lymph nodes (LN). One population (subset 1) was CD11c(low/+)/CD8alpha(-/low)/CD11b+/CD40+/CD86+. The other population (subset 2) was CD11c(high)/CD8alpha+/CD11b(low), and lacked CD40 and CD86. Only subset 1 was fluorescein 5-isothiocyanate (FITC+) following painting onto epidermis, and the appearance of such FITC+ cells in draining LN was inhibited by pertussis toxin. Mesenteric LN, spleen, and thymus contained only a single population of langerin+ DC, corresponding to peripheral LN subset 2. Unexpectedly, BG were absent from spleen CD8alpha+ DC despite expression of langerin, and these organelles were not induced by mAb 205C1. Collectively, we demonstrate that two langerin+ DC populations (subsets 1 and 2) co-exist in mouse lymphoid tissue. Subset 1 unequivocally identifies epidermal LC-derived DC. The distribution of subset 2 indicates a non-LC origin of these langerin+ cells. These findings should facilitate our understanding of the role played by langerin in lymphoid organ DC subsets.

Oral vaccination of mice with lipid-encapsulated Mycobacterium bovis BCG: anatomical sites of bacterial replication and immune activity.

Lipid microencapsulation of Mycobacterium bovis bacille Calmette-Guérin (BCG) produces an oral delivery vaccine that can establish systemic cell-mediated immune reactivity and protection against aerosol mycobacterial challenge in mice. Here, we describe the lymphatic and mucosal sites of bacterial replication, and location of Mycobacterium-specific IFN-gamma-secreting cell populations, following oral vaccination of BALB/c mice. Eight weeks following a single oral dose of lipid-encapsulated BCG, viable BCG organisms were recovered from the mesenteric lymph nodes (MLN) of 11/12 mice investigated (93%). Live bacteria were also occasionally recovered from the cervical lymph nodes (17%) and Peyer's patches (8%), but not from homogenates of the lungs or spleen. Strong Mycobacterium-specific IFN-gamma production was recorded among isolated splenocytes, but not among populations of mononuclear cells derived from the MLN or lungs. Oral vaccination of mice with lipid-encapsulated BCG thus appears to promote a state of systemic immunological reactivity more akin to that observed following parenteral rather than conventional oral vaccination, despite the fact that replicating bacilli are restricted to lymphatic tissues of the alimentary tract. Possible patterns of lymphocyte sensitization and trafficking are discussed.