Immune and mitogenic responses by BALB/c, C3H/HeJ, and nude mice to Brucella abortus bacterin and lipopolysaccharide.

The immunogenic and mitogenic properties of Brucella abortus 1119-3 bacterin (BA) and biologically active B. abortus lipopolysaccharide (BA-LPS) were studied using normal and athymic (nude) BALB/c and C3H/HeJ mice. Although BA stimulated 2-mercaptoethanol-sensitive (2-ME-S) primary and secondary antibody responses in all mice, nude mice, in contrast to normal BALB/c and C3H/HeJ mice, did not make substantial 2-mercaptoethanol-resistant (2-ME-R) antibody responses. Similarly, all mice injected with BA-LPS made 2-ME-S primary responses, and the secondary response of thymus-bearing mice contained a substantial 2-ME-R component. Collectively, these observations suggest that although both BA and BA-LPS can stimulate thymus-independent 2-ME-S antibody synthesis, thymus-derived cells are required for optimal immune responses containing a 2-ME-R component. The antibody responses of normal BALB/c and C3H/HeJ mice to BA and BA-LPS were qualitatively and quantitatively similar. Both BA and BA-LPS were mitogenic for spleen cells from normal and nude BALB/c and C3H/HeJ mice but not for thymus cells from normal BALB/c or C3H/HeJ mice, suggesting that both preparations are B-cell mitogens.