Fig. 1.

Age-associated differences in the LD₅₀s of mice infected with Y. pestis. (A) Young (2-month-old) female B10.T(6R) mice, male B10.T(6R) mice, and B6 mice were infected i.v. via the retro-orbital sinus with increasing doses of Y. pestis KIM5. After 21 days of monitoring, the LD₅₀ was calculated using log dose probit analysis (at a 95% confidence level). (B) LD₅₀s of middle-aged (5- to 12-month-old) female B10.T(6R) mice. Data represent the results of eight experiments for young male and female B10.T(6R) mice and two separate experiments for age-matched female C57BL/6N mice and middle-aged B10.T(6R) mice (n=6/dose group/experiment).