Recombinant interleukin-2-activated intracavitary lymphocytes: phenotypic characteristics and effector function

A preclinical study of intracavitary lymphocytes (ICL) from malignant effusions of cancer patients is described. The object of this study was to evaluate the antitumor potential of ICL as a baseline for developing adoptive immunotherapy trial for ovarian carcinoma patients. The main parameters studied were functional cytolytic activity of fresh and recombinant interleukin-2 (rIL-2)-activated ICL and their phenotypic characteristics. Spontaneous cytolytic activity of ICL was detected in all samples tested against natural killer (NK)-sensitive targets (K562), while very low activity was shown against NK-resistant targets (Daudi) and fresh tumor cells. Activation in culture with rIL-2 generated cytolytic activity against NK-resistant targets and significantly augmented NK activity. The pattern of antitumor lytic activity of ICL resembles lymphokine-activated killer cell activity and is non-major histocompatibility complex restricted against a variety of tumor targets. Phenotypic characterization of fresh ICL showed the predominance of CD3+ cells with the CD4/CD8 ratio resembling that of peripheral blood lymphocytes. During culture with rIL-2, changes in phenotypic expression of activated ICL were detected: enrichment in NKH1+ cells (up to 65%), of CD8+ (up to 70%), and very late antigen (VLA)-1+ cells (up to 54%), concomitantly with a decrease in CD4+ population. The NKH1, CD8, and VLA-1 expression peaked at 2 weeks in culture and coincided with peak cytolytic activity of cultured ICL. Depletion of CD8+ cells from activated ICL resulted in a decreased proportion of cells expressing the NKH1 and VLA-1 phenotype, whereas depletion CD4+ cells led to enrichment in CD8, NKH1, and VLA-1 antigens. Cytolytic activity was significantly increased in CD4 depleted population against NK-resistant and NK-sensitive targets. In this study we found that rIL-2 activation and culture of ICL generates killer activity against NK-resistant and fresh tumor targets and that enrichment in expression of NKH1, CD8, and VLA-1 antigens is associated with effector function.