Enhanced delayed hypersensitivity skin test reactivity with serial testing in healthy volunteers

Delayed hypersensitivity skin testing with multiple antigens is frequently used to evaluate immunopotentiation therapy in man. Since serial skin testing with a single antigen has been shown to augment the skin test response, the present study was undertaken to assess the effect of serial delayed hypersensitivity skin testing on skin test reactivity with multiple antigens. Each of twelve healthy volunteers received 0.1 ml of five antigens on two occassion, 6 weeks apart. The antigens used were streptokinase-streptodornase, Candida, Trichophyton, mumps and Mycobacterium tuberculosis (PPD). The results demonstrated enhancement of skin test reactivity in the majority of tests. Indeed, 38.9% of the tests which were negative with the first skin test ( less than 10 mm induration) converted to positive. Enhancement in reactivity was observed in the majority of test subjects with all antigens except PPD. Similar enhanced skin test reactivity was observed in fifteen additional subjects tested serially with Candida only. The observations in this study suggest that uncontrolled studies of immunopotentiation must be interpreted with caution since serial delayed hypersensitivity skin testing with single or multiple antigens results in enhanced skin test reactivity.