Salmonella typhimurium infection in calves: specific immune reactivity against O-antigenic polysaccharide detectable in in vitro assays

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Abstract
Peripheral blood lymphocytes collected from calves infected experimentally with S. typhimurium (O antigens 4,5,12) or Salmonella sp. serotype dublin (O 9,12) were stimulated with various bacterial cell envelope components, and their [3H]thymidine incorporation was measured. Peripheral blood lymphocytes from infected calves incorporated significantly more [3H]thymidine than peripheral blood lymphocytes from uninfected controls (P values ranged from < 0.05 to < 0.0005). The responder cell type was found in a B cell-depleted and T cell-enriched population. The Salmonella infections elicited T cell responses against at least 2 cell envelope components: a specific response against the O-antigenic polysaccharide chain of the lipopolysaccharide (this was evident in that a polysaccharide from S. enteritidis [O 9,12] which shares a trisaccharide structure [O antigen 12 determinant] with S. typhimurium stimulated [3H]thymidine uptake, which, although lower than in the homologous system, was significantly higher than that seen after incubation with unrelated Salmonella sp. serotype thompson polysaccharide); and a response against outer membrane proteins (porins), which are present in both S. typhimurium and Salmonella sp. serotype dublin. The experiments with peripheral blood lymphocytes from Salmonella sp. serotype dublin-infected calves gave results in excellent agreement with those obtained in S. typhimurium-infected calves.