Immunological consequences of tumor excision: from active immunity to immunological memory.

Excision of the immunogenic Meth-A fibrosarcoma during generation by the host of concomitant antitumor immunity resulted in the appearance in sequence of two qualitatively distinct states of post-excision immunity. Immunity expressed on the day of excision was dependent on Ly-1-2+, cyclophosphamide-sensitive T cells, whereas immunity expressed 2 weeks later was dependent on cyclophosphamide-resistant T cells which can be functionally eliminated by either anti-Ly-1 or anti-Ly-2 monoclonal antibody and complement. The data suggest that antitumor immunity expressed shortly after tumor excision represents active concomitant immunity that is acquired by the host before excision is performed. In contrast, immunity expressed 2 weeks later is based on immunological memory.