Spleen inflammation in mice infected with B. abortus . (A) Evolution of the average of spleen weights (as an indicator of inflammation) of CD-1 mice infected with virulent (2308 strain), vaccine-attenuated (S19 strain) and non-virulent (bvrS mutant) B. abortus strains during 25 weeks after inoculation. The abscissas axis (time after infection) of the inserted panel is expressed in logarithmic scale to allow a better understanding of spleen inflammation at the initial phases of infection. (B) Comparison of spleen size (left) and histological transversal sections stained with hematoxylin-eosine of normal spleen (upper panel) and B. abortus 2308 infected spleen, after 8 weeks pi (lower panel). Notice that the proportion between white pulp/red pulp in the normal spleen is close to 1/1, while in the infected spleen is close to 1/4. The histological section of normal mouse is from Dr Frank Voelker, Flagship Biosciences, with permission of Steve Pots Charting A New Course in Tissue Analysis .