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The cynomolgus monkey was studied as an animal model to investigate the cell-mediated immunity induced by vaccines. Optimal conditions are described to isolate peripheral blood lymphocytes. Lymphocyte transformation tests were performed with tetanus toxoid and smallpox vaccine. Antigen-specific lymphocyte transformations with smallpox vaccine could only be demonstrated when lymphocytes were obtained from vaccinated monkeys. Tetanus toxoid appeared to be a weak antigen. However, after adsorption of the toxoid to aluminum phosphate, a significant antigen-specific lymphocyte transformation was observed.

In comparison with the presently used potency test for diphtheria vaccine, in vitro examination of the immunogenicity of the vaccine would have great advantages. For this reason in vitro induction of diphtheria toxoid specific antibody synthesis in human peripheral blood lymphocytes cultivated in the presence of diphtheria toxoid was investigated. The results showed that a dose dependent synthesis of diphtheria antibody was induced by adsorbed diphtheria toxoid and combined vaccines containing the diphtheria toxoid component. Plain diphtheria toxoid appeared to be less immunogenic in comparison with adsorbed toxoid. There is some indication that the pertussis component had a stimulating effect on the diphtheria antibody synthesis. In conclusion, these results are promising for in vitro examination of the immunogenicity of diphtheria vaccines. The model will be validated for the routine control of diphtheria vaccine.