The activity of interferons was tested in ultraviolet light-induced skin tumors in mice. After the tumors were well established, they were injected and measured daily for 19 days. Mouse virus type (IF-alpha + IF-beta) and immune (IF-gamma) interferons were injected intralesionally into three groups of test animals and compared with a fourth group which received mock interferon (control). When used separately, virus type and immune interferons did not affect tumor growth; however, we observed regression in tumor size when the two interferons were used in combination.
