title: Effect of interleukin-12 on antitumor activity of human umbilical cord blood and bone marrow cytotoxic cells.
abstract: Interleukin (IL)-12, a natural killer (NK) cell stimulatory factor, is a heterodimeric cytokine that is known to be a potent activator of non-major histocompatibility complex-restricted cytotoxicity by peripheral blood-derived NK cells. NK cells (CD3-CD16+/CD56+) represent approximately 15% of human umbilical cord blood mononuclear cells (HUCB MNCs) and are known to be highly sensitive to activation by IL-2. In the present study, we monitored the effect of IL-12 on the cytotoxic activity, proliferation, and phenotypic expression of HUCB-derived resting and IL-2-activated cytotoxic cells and compared these parameters with those of bone marrow (BM)-derived cells. Lymphocytes were separated from HUCB by 3% gelatin sedimentation and incubated with IL-12 and/or IL-2 for 18 hours. At effector:target ratios of 40:1 and 20:1, IL-12 (50 U/mL) significantly increased both resting and IL-2-activated NK cell-mediated cytotoxicity in a standard 51Cr-release assay against both NK-sensitive (K562) and NK-resistant (Colo-205) cell lines. In addition, resting and IL-2-activated cytotoxic cells derived from HUCB exhibited superior cytolytic ability compared with BM-derived cells. This increase was observed in resting cells as well as in those that were preincubated with IL-12. Moreover, HUCB-derived cells were found to be more sensitive to IL-12 activation than cytotoxic cells from BM. To evaluate the involvement of accessory cells, NK cells were purified from HUCB using immunomagnetic beads, and these cells were found to have a lower response to treatment with IL-12 than unpurified populations. HUCB MNCs exhibited a nonsignificant increase in proliferation after IL-12 treatment and were better able to respond to IL-12 activation than BM MNCs. Following an 18-hour incubation, IL-12 was able to cause upregulation of CD25 and CD69 activation antigens, whereas no significant change in expression of CD16 and CD56 NK cell surface antigens, CD3 on T cells, or IL-12 receptor was observed. Similarly, IL-12 did not affect NK cell:target cell conjugation as assessed by fluorescence-activated cell sorting. Our results indicate that HUCB-derived NK-mediated cytotoxic capabilities can be increased by IL-12, a finding that may have clinical relevance.
authors.affiliation: Department of Bone Marrow Transplantation and Israel National Cord Blood Bank, Hadassah University Hospital, Jerusalem.
authors.forename: R
authors.initials: R
authors.lastname: Condiotti
authors.forename: A
authors.initials: A
authors.lastname: Nagler
mesh_terms: D015703:Antigens, CD / Q000097:blood; D000945:Antigens, Differentiation, T-Lymphocyte / Q000097:blood; D000954:Antigens, Surface; D015415:Biomarkers; D002455:Cell Division / Q000276:immunology; D002478:Cells, Cultured; D003602:Cytotoxicity, Immunologic; D005312:Fetal Blood / Q000276:immunology*; D006801:Humans; D016130:Immunophenotyping; D018664:Interleukin-12 / Q000494:pharmacology*; D007694:Killer Cells, Natural / Q000276:immunology*; D037181:Lectins, C-Type; D015375:Receptors, Interleukin-2 / Q000097:blood; D015854:Up-Regulation; D000099192:CD69 Antigens
chemical_list: D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D000954:Antigens, Surface; D015415:Biomarkers; D018664:Interleukin-12; D037181:Lectins, C-Type; D015375:Receptors, Interleukin-2; D000099192:CD69 Antigens