RT Journal Article SR Electronic T1 Appearance and Phenotypic Characterization of Circulating Leu 19+ Cells in Cancer Patients Receiving Recombinant Interleukin 2 JF Cancer Research JO Cancer Res FD American Association for Cancer Research SP 6597 OP 6602 VO 48 IS 22 A1 Ellis, Thomas M. A1 Creekmore, Stephen P. A1 McMannis, John D. A1 Braun, Donald P. A1 Harris, Jules A. A1 Fisher, Richard I. YR 1988 UL http://cancerres.aacrjournals.org/content/48/22/6597.abstract AB The effects of recombinant interleukin 2 (rIL-2) therapy on peripheral blood mononuclear cells expressing the Leu 19 surface marker were evaluated in 20 cancer patients. Leu 19 is a protein with a molecular weight of 220,000 expressed on 15% of normal peripheral blood mononuclear cells and is found on a majority of cells that mediate non-major histocompatibility complex-restricted cytotoxicity. Increased relative and absolute numbers of circulating Leu 19+ cells were observed in all patients receiving rIL-2. Increases in Leu 19+ cells were due in part to the development of a subpopulation of “bright” Leu 19+ cells (Leu 19b+) that possessed a higher density of membrane Leu 19 antigen than Leu 19+ cells assayed prior to therapy. Further characterization of rIL-2 induced Leu 19+ cells by dual immunofluorescence revealed considerable phenotypic heterogeneity within this population based on the coexpression of “dim” CD8 (CD8d+), CD16, and CD2 markers. The percentage of Leu 19+ CD8d+ cells was increased during rIL-2 therapy and comprised up to 60% of all circulating Leu 19+ cells. CD16+ and CD16-subsets of Leu 19+ cells were also increased by rIL-2. The density of CD16 antigen coexpression varied inversely with the density of Leu 19. Conversely, whereas the percentage of Leu 19 cells coexpressing CD2 was also increased by rIL-2 administration, the density of CD2 antigen expression was higher on the Leu 19b+ subset of cells. The development of circulating lymphokine-activated killer activity in three patients was temporally associated with the development of increased levels of circulating Leu 19+ cells. These studies demonstrate that rIL-2 administration induces preferential increases in cells expressing the natural killer and lymphokine-activated killer cell-associated marker Leu 19 and that these increases are associated with the development of circulating lymphokine-activated killer activity. Furthermore, Leu 19+ cells are comprised of phenotypically heterogeneous subsets which undergo characteristic changes during rIL-2 administration. ©1988 American Association for Cancer Research.