In vivo and in vitro boosting effects of tuberculin skin tests in guinea-pigs immunized with living BCG or with killed Mycobacterium tuberculosis.

Eight weeks after the onset of immunization with living BCG vaccine or with heat-killed, dried Mycobacterium tuberculosis in paraffin oil (TB), guinea-pigs were skin tested with small doses of tuberculin PPD. Three weeks later the effect of these tests on skin reactions and on lymphocyte transformation (LT) responses of lymph node lymphocytes (LNL) or peripheral blood lymphocytes (PBL) was estimated by a comparison with non-tested groups. For both immunogens, the skin test after 8 weeks significantly enhanced skin reactions, particularly to low tuberculin doses. In the BCG-vaccinated guinea-pigs the LT responses of both cell types were significantly enhanced by the skin test after 8 weeks, whereas the LT responses from the TB-immunized guinea-pigs were not affected. Therefore, in the planning and interpretation of in vitro tests of cellular immunity, possible effects from previously applied skin tests should be taken into consideration.