Expression of Leucocyte Function-associated Antigen-1 and Intercellular Adhesion Molecule-1 in the Lungs of Pigs Infected with Actinobacillus pleuropneumoniae

Summary The aim of this study was to determine the expression of leucocyte function-associated antigen (LFA)-1 (CD11a/CD18) by neutrophils and intercellular adhesion molecule (ICAM)-1 (CD54) by endothelial cells in the lungs of pigs that had been infected experimentally with Actinobacillus pleuropneumoniae . Sixty-four 7-week-old conventional pigs were allocated randomly into infected ( n  = 40) or control ( n  = 24) groups. Five infected and three uninfected pigs were killed at 3, 6, 9, 12, 24, 36, 48 and 60 h post inoculation (hpi). Strong immunohistochemical expression of LFA-1 and ICAM-1 was detected frequently in neutrophils in the alveolar space and in endothelial cells in the capillaries of the alveolar septa, respectively. LFA-1 and ICAM-1 expression appeared to correlate with the onset of neutrophil infiltration into the alveolar space. The interaction between ICAM-1 and LFA-1 may be associated with the adherence of neutrophils to vascular endothelium, thereby permitting transmigration of these cells into inflamed lung.