Comparison of lung dendritic cells and B cells in stimulating naive antigen-specific T cells

Dendritic cells (DCs) are specialized APCs that are important in priming na ive T cells and can be manipulated in vitro and in vivo to enhance immuniza tions against microorganisms and tumors. A limitation in the development of suitable immunotherapeutic vaccines for the lung is incomplete information on the role of DCs and other potential APCs in the lung in priming naive T cells. In the current study, we analyzed the relative contributions of mur ine lung DCs and B cells to process and present OVA to naive CD4(+) OVA(323 -339)-specific (DO11.10) T cells in vitro. We also examined their expressio n of NHC class II and accessory molecules before and after maturation in cu lture. Similar to DCs from other sites, freshly isolated lung DCs can proce ss OVA, spontaneously up-regulate MHC class II and accessory molecules duri ng overnight culture, and stimulate naive T cells in an Ag-specific manner. In contrast, freshly isolated lung B cells were unable to both process and present native OVA. Furthermore, under conditions of limited OVA(323-339) peptide exposure, B cells had a significantly diminished capacity to stimul ate T cells, and this correlated,vith a decreased density of both MHC class II and important costimulatory molecules as compared with lung DCs.