||P.382 caption to Fig. 10.1: "The course of a typical acute infection: 1. The level of infectious agent increases as the pathogen replicates. 2. When numbers of the pathogen exceed the threshold dose of antigen required for an adaptive response, the response is initiated the pathogen continues to grow, retarded only by the innate and nonadaptive responses. At this stage, immunological memory also starts to be induced. 3. After 4-5 days, effector cells and molecules of the adaptive response start to clear the infection. 4. When the infection is cleared and the dose of antigen falls below the response threshold, the response ceases, but antibody, residual effector cells, and also immunological memory provide lasting protection against reinfection in most cases."