Immune reactivity to autochthonous ovine squamous cell carcinomata

The immune reactivity of tumor-bearing sheep to autochthonous tumor cells was investigated in the efferent lymph of a lymph node distant from the primary tumor site. This was done while the primary tumor was in situ and after its resection. The immune response to challenge with tumor cells while the primary tumor was in situ was associated with the detection of antibodies which were specific for the tumor cells but did not cause their demise. However, both humoral and cellular cytotoxic reactivities were detected in the lymph following removal of the primary tumor and rechallenge with tumor cells. This response had the characteristic of a secondary immune response which indicates sensitization to tumor antigens by the host. Thus the presence of the primary tumor has interfered with pre-existing host immunity.