Antitumor immunity induced by laser immunotherapy and its adoptive transfer

The ideal cancer treatment modality should not only cause tumor regression and eradication but also induce a systemic antitumor immunity, which is ess ential for control of metastatic tumors and for long-term tumor resistance. Laser immunotherapy using a laser, a laser-absorbing dye, and an immunoadj uvant has induced such long-term immunity in treatment of a mammary metasta tic tumor. The successfully treated rats established total resistance to mu ltiple subsequent tumor challenges, To further study the mechanisms of the antitumor immunity induced by this novel treatment modality, passive adopti ve transfer was performed using splenocytes as immune cells. The spleen cel ls that were harvested from successfully treated tumor-bearing rats provide d 100% immunity in the naive recipients. The passively protected first coho rt rats were immune to tumor challenge with an increased tumor dose; their splenocytes also prevented the establishment of tumor in the second cohort of naive recipient rats, This immunity transfer was accomplished without th e usually required T-cell suppression in recipients.