T-CELL PRIMING INSITU BY INTRATRACHEALLY INSTILLED ANTIGEN-PULSED DENDRITIC CELLS

In the present study, splenic dendritic cells (DC) and alveolar macrop hages (AM) were pulsed with antigen in vitro and subsequently intratra cheally instilled to test whether these cells have the capacity to sen sitize T cells in the draining lymph nodes of the lung. The data demon strate that antigen-pulsed DC, instilled in the bronchoalveolar lumen, induce antigen-specific T cell priming in vivo in the draining lymph nodes. T cell priming is only seen with viable but not with killed ant igen-pulsed DC. Amounts as low as 5 x 10(3) to 10 x 10(3) cells can st ill induce some responsiveness. In addition, it was found that instill ation of viable as well as killed pulsed Ia-negative AM also leads to T cell priming, although about 10 times higher numbers of cells had to be used in comparison with DC. The results suggest that DC instilled in the bronchoalveolar lumen present antigen directly to naive T cells , whereas for AM other mechanisms are involved.