[Anti-Brucella immunity transferred by immune serum and that transferred by splenic lymphocytes cannot be added]

Immune serum and spleen cells from mice vaccinated with a cell-wall fraction (PG) from Brucella were previously shown to transfer a good protection to mice against a virulent Brucella challenge. This protection estimated by spleen and liver time-course infection was similar to that afforded by vaccination. In present experiments, DBA/2 mice were first transferred with either immune serum from infected mice, splenic cells from mice intravenously vaccinated with PG fraction 28 days previously, or both immune serum and splenic cells. In this case, the serum was either injected before the challenge, as were the splenic cells, or 2 days after it in order to reduce the lowering effect of the serum on level of initial colonization of the spleen. The transferred mice were then intravenously challenged with the virulent strain B. abortus 544 and liver and spleen counts were performed on groups of five mice weekly up to six weeks. Immune serum and splenic cells from vaccinated mice were again shown to strongly reduce the time-course of splenic infection. However addition of both effects was observed for a short time only two and three weeks post-challenge and only when the serum was injected after the challenge. In contrast, no additive or even an antagonistic effect was observed after the 21st day. Liver infection was not notably modified by both immune serum or splenic cells (except increment of initial colonisation by serum) until the 21st day when both helped reduce the course of infection. However again no additive effect was observed.(ABSTRACT TRUNCATED AT 250 WORDS)