The sequence of enhanced cellular activity and protective humoral factors in murine pertussis immunity.

1. The time relationships of delayed type hypersensitivity, cellular immunity and protective circulating immunoglobulin production assumed an unexpected pattern in mice responding to sublethal pulmonary infection with Bordetella pertussis. 2. Cellular immunity, characterized by an intracellular bacterial steady state appeared early. Initially, it was not demonstrably associated with either delayed type hypersensitivity or effective levels of circulating protective antibody. 3. The appearance, after 6 weeks or more, of protective levels of antibody was associated with bacteriological clearance accompanied by loss of cellular immunity.