Pertussis toxin treatment in vivo reduces surface expression of the adhesion integrin leukocyte function antigen-1...

Pertussis toxin treatment in macaques inhibits lymphocyte extravasation from the blood and leads to transient lymphocytosis and leukocytosis. We examined lymphocyte adhesion molecules known to be involved in the extravasation process to find possible mechanisms for the effects of pertussis toxin treatment. The two subunits of LFA-1, CD11a and CD18, showed decreased surface expression on lymphocytes from pertussis toxin treated animals compared to untreated animals. The adhesion molecule CD44, and the alpha subunit of the integrin VLA-4 (CD49d) were not decreased by pertussis toxin treatment. Lower surface expression of CD11a and CD18 was observed on all lymphocyte subsets and was correlated inversely with the extent of lymphocytosis. The magnitude of lymphocytosis after pertussis toxin treatment was higher in SIV-infected macaques than in uninfected animals. However, changes in LFA-1 levels were similar in both groups. These data show that LFA-1 surface levels are affected by pertussis toxin in vivo and this change may account in part, for the ability of pertussis toxin to induce lymphocytosis.