Mice injected intranasally (it.n.) and intraperitoneally (i.p.) with a nonlethal dose (2.5 x 10(5) colony-forming units) of live Bordetella pertussis were examined for 50 days for infection, respiratory tract immunoglobulins (Ig), changes in serum Ig, and histamine sensitivity. With mice infected it.n., respiratory infection markedly declined between day 20 and day 30. Ig classes (A, G(1), G(2a), G(2b), but no M), which had specificity for B. pertussis, were present in tracheobronchial wash (TBW) by day 15; by day 50, TBW immunodiffusion and immunoelectrophoretic precipitin bands were more intense. A sharp rise in serum IgA after day 30 was the only significant change relative to controls among the five serum Ig examined. A high degree of histamine sensitivity developed by day 15 to 20 and persisted for the 50 days. With mice inoculated i.p., no bacteria were recovered, no Ig or only traces were found in TBW and IgA only was specific, and no significant changes in the serum Ig relative to controls occurred. Histamine sensitivity developed somewhat more slowly and to a lesser degree than in it.n.-injected mice but persisted for the 50 days. A similar small number of killed bacteria (pertussis vaccine) injected it.n. or i.p. likewise induced slowly developing histamine sensitivity in contrast to published reports of 4 to 5 day peak sensitivity and decline following i.p. injection of 10(9) or more killed bacteria.