Induction of autoantibodies and circulating immune complexes in mice after injection of Brucella fraction "PI" or inoculation with live Brucella suis.

"PI", a vaccinating fraction with B mitogenic and polyclonal activator (PCA) activity extracted from Brucella melitensis, was i. p. injected into B6 and DB mice. In B6 mice, this led to an important but transient increase in the level of anti-ssDNA antibodies, the induction of rheumatoid factor (RF) and the appearance of circulating immune complexes (CIC). In DB mice, on the other hand, the only significant effect consisted of a slight and ephemeral peak of CIC in sera from day 7. Similarly, while i. v. inoculation of live B. suis did not influence the levels of anti-ssDNA, RF or CIC in DB mice, in the B6 mice it exerted effects which were comparable to those of PI but considerably weaker, more transient and somewhat delayed. These results are discussed in terms of the importance and significance of strain-dependence for the induction of autoimmune phenomena by PCA and microbial infections.