IMMUNE AND PATHOLOGICAL RESPONSES IN MICE INFECTED WITH BRUCELLA-ABORTUS-19, BRUCELLA-ABORTUS-RB51, OR BRUCELLA-ABORTUS-2308

Immune and pathologic responses were measured for 20 weeks after infec tion of mice with Brucella abortus 19, RB51, or 2308. Live bacteria an d bacterial antigens of 19 and RB51 persisted in spleens for 10 and 4 weeks after infection, respectively, whereas 2308 bacteria and bacteri al antigens persisted for at least 20 weeks. Small germinal centers an d profound lymphoid depletion occurred in spleens of mice during the f irst 4 weeks of infection with strain 19 or 2308; however, mice infect ed with strain RB51 had much larger germinal centers but no lymphoid d epletion. At 4 weeks, only spleen cells from RB51-infected mice prolif erated when incubated with 2308 bacteria. Large germinal centers in th e spleen and spleen cell proliferative responses to 2308 did not appea r in strain 19-infected mice until 6 weeks or in strain 2308-infected mice until 10 weeks. Similar proliferative responses to 2308 occurred in mice infected with strain 19 or RB51 at 6 weeks and in mice infecte d with strain 19, RB51, or 2308 at 10 weeks. However, at 20 weeks, spl een cell proliferative responses to 2308 occurred in mice infected wit h strain 19 or 2308 but not in mice infected with strain RB51. Mice in fected with strain RB51 had lower and less persistent antibody titers to 2308 than did mice infected with strain 19 or 2308. Collectively, t hese results indicate that RB51-infected mice have less persistent imm une responses to 2308 than do mice infected with 19 or 2308. The short er duration of the responses probably resulted because RB51 is conside rably less pathogenic and is cleared more rapidly from mice than are 1 9 and 2308.