Defective natural killer activity within human ovarian tumors: Low numbers of morphologically defined effectors present in situ

Tumor-associated lymphocytes (TAL) were isolated from 17 ascites and 7 solid ovarian carcinomas. TAL had defective natural killer (NK) activity against K562. Large granular lymphocytes, the morphologically identified effectors of NK activity, were poorly represented in TAL from ovarian carcinomas as compared to peripheral blood lymphocytes from the same patients or from normal donors. Similar results were obtained when effectors of NK activity were identified with an anti-NK (HNK-1) monoclonal antibody. When four TAL preparations were separated on discontinuous Percoll gradients, they were able to be enriched for NK activity and large granular lymphocyte morphology in the lower density fractions as observed with blood. These observations suggested that a low concentration of the relevant effector cells was the major factor determining the defective NK cytotoxicity of lymphoid cells associated with these human neoplasms.