Studies on the lymphocytosis induced by pertussis toxin

Pertussis toxin (PT), from Bordetella pertussis, causes lymphocytosis and increased IL-4 and IgE secretion. The lymphocytosis is associated with impaired entry of lymphocytes into lymph nodes. The dose response of PT on IL-4 secretion was found to be similar to those for lymphocytosis and IgE production. These findings are consistent with the possibility that increased IL-4 production by PT may be related to its effect on lymphocyte circulation. The possibility that PT may selectively influence the entry into lymph nodes of subsets identified with CD45RB, CD4 or CD8 was tested by assessing the phenotype of lymph node cells. PT had no significant effect on the proportion of cells with these markers, either in unimmunized or in immunized mice. These findings indicate that PT does not selectively impair entry of these lymphocyte subsets into lymph nodes.