Figure 8.

Schematic representation of the lesions in CD34^−/− dendritic cell (DC) function in vivo. The red crosses indicate the hypothesized defect in Cd34^−/− mice. Normally, DC precursors leave the circulation, enter the lung parenchyma, and subsequently cross the basement membrane and epithelia to enter the alveolar space. Upon antigen uptake these cells then traffic back into the lung parenchyma and enter the lymphatic circulation on their way to the draining lymph node for antigen presentation to T cells. Cd34^−/− DCs fail to efficiently traffic from the alveolar space and migrate to the draining node and instead accumulate in the parenchyma. Likewise, recruited DCs from the circulation accumulate in the parenchyma and fail to enter the alveolar space in response to inflammation.