Published online by Cambridge University Press: 15 May 2009
The survival rate of mice actively or passively immunized against intracerebral challenge with Bordetella pertussis, was independent of the size of challenge dose within the range of 20–2000 LD.
This unexpected result appears to be due to the anatomical peculiarities of the infected organ, in which circulating antibody does not pass the normal blood-brain barrier easily. The pertussis infection does not cause sufficient inflammation to induce a pathological increase in the permeability of the barrier until the number of living microbes in the brain reaches 10 to 10. Since this stage in the brain consistently occurs after 4–5 days, independently of the size of the inoculum within the range 20–2000 LD, the outcome of infection in the immunized animal depends solely on the degree of specific immunity.
In the non-immune mouse, the increase in permeability of the barrier persists until death. In the immunized mouse, the elimination of the infection leads to a restoration of the normal barrier at about the 6th day.