Tumor-associated lymphoid cells: analysis of host cells that bind to syngeneic and allogeneic tumor cells shortly after tumor administration.

A single intraperitoneal injection of irradiated EL-4 leukemia into syngeneic hosts induced in vivo immunity and in vitro cell-mediated response against EL-4. A nonadherent, theta-positive, peritoneal exudate lymphocyte fraction that bound to and lysed EL-4 in vitro was isolated from the tumor site. This system allowed the study of immune processes involving host lymphocytes as early as 3 days after tumor inoculation.