Effects of NO2on immune responses in pulmonary lymph of sheep

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Abstract
Sheep in which the efferent duct of the caudal mediastinal lymph node was cannulated were exposed to 5 ppm NO2, 1.5 h/day for 10 or 11 days. Immune responses were assessed by measuring the daily output of hemolytic plaque-forming cells (PFC) in pulmonary lymph, following intrabronchial immunization with horse red blood cells (HRBC) and phytohemagglutinin- (PHA) induced transformation of blood and pulmonary lymph lymphocytes. Sheep immunized 2 days after termination of NO2 exposure had reduced outputs of PFC as compared to those seen in sheep challenged 4 days after NO2 exposure. Animals immunized 4 days after NO2 exposure had outputs similar to those of air control sheep. A reduction of 38-87% in the transformation index of blood and pulmonary lymph lymphocytes was observed in sheep exposed to NO2. Intermittent, short-term exposure to 5 ppm NO2 may temporarily alter pulmonary immune responsiveness.