Thymic responses to antigen challenge. I. Tumor cells induced phenotypic and functional changes in vivo

Thymocytes from mice bearing a footpad injection of 2 x 10(6) syngeneic tumor cells exhibited increased in vitro responsiveness to concanavalin A and allogeneic cells in the mixed lymphocyte reaction. A higher proportion of Thy 1 dull cells (assayed by flow microfluorometry) was seen among thymocytes taken from normal, or control injected mice, relative to tumor injected mice. Injection of culture supernatant from the tumor cells induced no phenotypic or functional shifts among thymocytes, nor was any evidence of viral gp70 antigen expression found in the thymocyte preparation. These findings support the notion that viruses or viral products are not involved in induction of these shifts; however, lymphokine production by host peripheral cells has not been ruled out.