Hypersensitivity Reactions at Tumor Sites1

Induced cell-mediated immunity (hypersensitivity) resulted in selective injury and eradication of premalignant and malignant epidermal lesions in man with minimal or no adverse effects on normal tissues. Immune challenge produced resolu tion of more than 95% premalignant kératoses,superficial basal cell carcinomas, and squamous cell carcinomas in situ in 50 patients without recurrences for observation periods of up to 5 years. During the reaction to challenge, multiplication of normal cells and healing proceeded while their malignant and premalignant counterparts were being destroyed. Resistance did not develop on up to 7 successive courses of immunotherapy. The incidence of new lesions was decreased following immunotherapy in patients with otherwise persistent develop ment of new lesions as compared to treatment with standard modalities. Systemic toxicity or generalized immune reactions did not occur. Immunity was transferred to nonsensitized patients by peripheral leukocytes from sensitized patients. Challenge reactions in patients with transferred immunity resulted in the same effects on epidermal neoplasms as in patients who had been sensitized by direct exposure to the sensitizer. The data demonstrate that specific cell-mediated hypersensitivity can be induced by simple chemicals in man which results in lasting involution of premalignant and malignant neoplasms. Studies are warranted to determine whether analogous principles can be extended to tumor biology in general.