THE ANTIGEN-PRESENTING ACTIVITIES OF IA(-NODE AFTER AN AIRWAY CHALLENGE WITH SOLUBLE-ANTIGEN() DENDRITIC CELLS SHIFT DYNAMICALLY FROM LUNG TO LYMPH)

Dendritic cells (DC) are widely distributed in the lung where they are distinguished by their morphology and class II major histocompatibili ty complex (Ia) antigen expression. Although a role for DC as pulmonar y antigen-presenting cell (APC) has been suggested, little is currentl y known concerning how these cells respond to inhaled antigens in vivo . Hen-egg lysozyme (HEL) was injected intratracheally into Lewis rats; DC were subsequently purified from the lung and regional lymph nodes (LN) at intervals of up to 14 d and examined for their ability to stim ulate the proliferation of HEL-immune T cells in vitro in the absence of added HEL. Pulmonary DC displayed APC activities at 3 h and for up to 7 d after the injection of antigen. Dendritic cells in the draining hilar LN showed APC activities that appeared at 24 h, peaked at day 3 , and then diminished progressively. After the primary sensitization, HEL-immune T cells were detected in hilar LN but not in the lung. A se cond airway challenge with HEL at day 14 yielded an antigen-specific p ulmonary immune response, characterized histologically by the accumula tion of mononuclear cells around lung venules. We conclude that APC ac tivities shift from lung to lymph node during the response to inhaled antigen.