Generation of MHC-nonrestricted and restricted oncolytic subsets from human bone marrow

Abstract

We analyzed the cytotoxicity and characterized the phenotype of oncolytic bone marrow (BM) lymphocyte subsets generated in vitro by interleukin-2 (IL-2) and stimulator cells (SC). Two irradiated B-lymphoblastoid cell lines (Daudi and EBV-transformed BSM) and fresh human acute myelogenous leukemia (AML) were used as SC. Stimulation with Daudi and IL-2 resulted in a substantial increase in cytotoxic activity (100- to 1000-fold) against a broad range of tumor targets, and total cellular expansion was higher compared to stimulation with IL-2 alone. The most prominent increase was observed in the CD16 + and CD56 +/CD3 − natural killer (NK) cell subset; however, a significant increase was also observed in CD56 +/CD3 + T cells. Functional analysis of Daudi- and IL-2-generated subsets using fluorescence-activated cell sorting (FACS) revealed that most of the lytic activity was mediated by NK cells. Significant potentiation of oncolytic activity and cell growth was also seen in the cultures stimulated with BSM or fresh AML and IL-2. The highest oncolytic activity in the latter cultures was mediated primarily by CD8 +, CD3 +, and CD56 − T cells, although NK cells also participated in cytotoxic activity. The T cell-mediated cytotoxicity was restricted by the major histocompatibility complex (MHC), since most cytotoxicity could be blocked by HLA I antibodies. Additionally, we observed that optimum stimulation of cytotoxicity required effector cell-stimulator cell contact. These data indicate that depending on the tumor used for stimulation, different lymphocyte subsets may be generated in IL-2 cultures. These different approaches may be useful in both specific and nonspecific immunotherapy.