Cytotoxin B of C. difficile was highly purified by selective ammonium sulfate precipitation, Biogel A5m chromatography, phenyl boronate hydrophobic interaction chromatography and ultracentrifugation. The final cytotoxic product had a specific activity of 7.8 × 108
protein and showed a single protein band with an estimated molecular weight of 163000 when subjected to SDS‐PAGE. Immunoelectrophoresis of the final product showed a single precipitin arc. The addition of cytotoxin B to imidazole‐HCl buffer (pH 7.4) containing MgSO4, KCl and the substrate 2‐phosphoglycerate resulted in the formation of phosphoenolpyruvate as demonstrated by spectrophotometric analysis. Phosphoglycerate conversion was absent when the cytotoxin was heat‐inactivated of reacted with specific antitoxin prior to assay.
Splenic lymphocytes from preleukemic AKR mice are capable of participating in various cell-mediated immune responses. Spleen cells from AKR mice aged 1 to 10 months produced a significant graft-versus-host reaction when injected into 8-day-old AKR × C57Bl/6 F
1
hybrids. Splenic lymphocytes from similarly aged mice were also capable of responding to allogenic stimulation in a mixed lymphocyte reaction. AKR mice aged 1 to 10 months developed a contact sensitivity response to picryl chloride. It was concluded that mice of this high-leukemic strain have a competent cell-mediated immune system and there is no depression of immunity during the preleukemic period.
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