Proliferative capacity of marmoset lymphocytes after tetanus vaccination and lack of 2,3,7,8-tetrachlorodibenzo-p-dioxin to reduce a booster effect.

Marmosets (Callithrix jacchus) were vaccinated with tetanus toxoid and boostered 3 months and 1 year following the initial immunization. During this period, the proliferative response of lymphocytes (3H-thymidine incorporation) to the recall antigen was measured in vitro in blood samples 7 times. The experimental procedure proved to be suitable to monitor a defined but complex function of the immune system, and to assess possible substance-induced alterations with minimal stress or discomfort for the non-human primates. As a first example, a possible interference by a single very small dose (100 ng/kg body weight) of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) given at the time of the second booster was evaluated. No reduction in the in vitro response of the lymphocytes to recall antigen was observed under the experimental conditions used, and the extent of the 3H-thymidine incorporation was not significantly different in the groups. When the ratio of the responses between the first and the second booster was taken as a measure, there was a slight but statistically significant increase in this ratio for the lymphocytes of the TCDD-treated marmosets over that of reference animals. The limitations of these attempts to develop a test system and evaluate a substance-induced effect, and possible improvements of the test, e.g. with multivaccination, are discussed. It is suggested to use this approach also after routine multivaccination in children to assess possible substance-induced effects on immunological variables. This would allow an excellent comparison of experimental and clinical data obtained in primates with an identical technology.