"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.

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PubMedDate not supplied

Response of high and low antibody producer to Brucella.

Biozzi's high and low lines of antibody producers have been applied to an analysis of murine in vivo responses to Brucella. High responders (H/Ab) are better producers of anti-Brucella antibodies and of Brucella induced interferon than low responders (L/Ab). There is no interstrain difference between H/Ab and L/Ab mice as regards to cutaneous hypersensitivity reactions to melitin. Non-immunized L/Ab mice are more resistant to infection with live Brucella than H/Ab. Immunization with formalin killed Brucella leads to a specific protection of both H/Ab and L/Ab mice but magnifies their inter-strain differences: L/Ab are much better protected by preimmunization than H/Ab. The difference between H/Ab and L/Ab mice is not related to an earlier clearance of intravenously inoculated bacteria from the blood stream but to later events affecting the balance between multiplication and digestion of the injected bacteria in the spleen. The lower resistance of H/Ab mice is not due to negative, facilitating-like, activities of immune antibodies: on the contrary, these are shown to have protective properties. These results are discussed in terms of their contribution to present knowledge on Biozzi's mice and their macrophagic functions, on the relations between interferon synthesis and the immune system, and on the mechanism of natural and post-vaccinal protection toward Brucella.

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PubMedDate not supplied

Studies on the genetic control of murine humoral response to immunization with a peptidoglycan-containing fraction extracted from Brucella melitensis.

A peptidoglycan containing fraction (fraction "5") extracted from Brucella melitensis has been injected in low infra-vaccinating doses into inbred mice. The genetic control of the resulting anti-Brucella humoral response has been studied in the C57BL/6 "good responder" X DBA2 "low responder" model. The results observed in F1, F2 and reciprocal backcrosses show that the "good responder" character, although transmitted as a dominant trait, is under polygenic control and independent of H2 haplotype, Ig allotype, sexual chromosoms or the "d" coat color gene. On the other hand, the phenotypic expression of at least one of the genes involved is sex-limited and influenced by hormonal environmental factors. Moreover the expression in females of one of these sex-dependent genes is associated with the "b" coat color gene. These results are discussed in terms of their possible relevance in spontaneous or vaccinal resistance to experimental brucellosis, of the relative role of the peptidoglycan and lipoprotein moieties in fraction "5" and of the possible importance of sex-dependent and chromosome 4-linked genetic factors for B-cell functions.

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