Flow cytometric immunophenotyping of peripheral blood lymphocyte subsets is a powerful tool for evaluating cellular immunity and monitoring immune-mediated diseases. The numbers and proportions of blood lymphocyte subsets are influenced by factors such as gender, age, ethnicity, and lifestyle. This study aimed to establish reference ranges for peripheral blood lymphocyte subsets in a healthy Korean population. Blood samples from 294 healthy adults were collected. Lymphocyte subsets were analyzed using a single-platform method with a flow cytometer; white blood cells and lymphocytes were analyzed using an automated hematology analyzer. The mean value of the white blood cell count was 5,665 cells/µl, and the mean values of the subtype counts (percentages) were as follows: lymphocytes, 1,928 cells/µl (35.08%); CD3+ cells, 1,305 cells/µl (67.53%); CD3+CD4+ cells, 787 cells/µl (40.55%); CD3+CD8+ cells, 479 cells/µl (25.23%); CD3-CD19+ cells, 203 cells/µl (10.43%); and CD3-CD56+ cells, 300 cells/µl (15.63%). Additionally, the CD4+/CD8+ ratio was 1.81. In this study, gender and age significantly influenced blood lymphocyte subsets. Our results demonstrate that, as with other populations, a healthy Korean population has its own, region-specific, lymphocyte subset reference ranges.

Abstract. Cytotoxicity assays with patient peripheral blood mononuclear cell (PBMC)-derived natural killer (NK) cells are useful in evaluating the innate immunity of patients with cancer. However, the size of the NK cell population in PBMC preparations may have significant effects on the assay outcome. Therefore, the present study examined the effect of NK cell frequency in a cytotoxicity system to investigate NK cell immunity in post-surgical colorectal cancer patients. For this, hemacytotoxicity was assessed using PBMC preparations, and lymphocyte subset populations were analyzed in samples obtained from 47 patients and 45 healthy volunteers. In addition, a new theoretical parameter, the 'NK lytic index', was termed to represent the per-cell cytotoxicity and compensate for the NK cell frequency effect during PBMC preparations. Notably, the patterns of hemacytotoxicity and NK lytic index did not coincide in follow-up studies with consecutive patients following surgical intervention. In addition, it was determined that NK cell NKG2D expression influences NK lytic index, but not hemacytotoxicity. Transforming growth factor (TGF)-β-bound lymphocytes influenced hemacytotoxicity and NK lytic index. These findings indicate that total cell activity (hemacytotoxicity) is not a sum of per-cell activities (NK lytic indexes), suggesting that clinicians should employ NK lytic index in addition to hemacytotoxicity in order to precisely determine how to enhance NK cell immunity in patients with cancer, either focusing on recovering the number of NK cells or boosting NK cell activity in single cell levels, or both. IntroductionNatural killer (NK) cells, which serve critical roles in cancer immunity, are regarded as the first line of defense to eliminate transformed or malignant tumor cells (1). Therefore, multiple clinical laboratories have examined the implications of NK cell-mediated immunity in cancer and demonstrated that NK cells are functionally impaired in the majority of forms of cancer (2-4). Therefore, clinical attempts to boost endogenous NK cell activity, using biological response modifiers or the adoptive transfer of in vitro activated NK cells, have been investigated for the treatment of patients with cancer (5,6). However, a reliable tool to evaluate NK cell activity on a per-cell basis in each patient should be described prior to clinical application in order to design optimal treatment regimens, particularly since the degree of impaired NK cell activity and its etiology differ from patient to patient (7-9).In vitro cytotoxicity assays have been widely used in clinical laboratories to study NK cell function in patients with cancer. A feature of this assay system is the co-culture of effector cells with their specific target cells over a range of ratios, in which the cytotoxicity of NK cells against their target cells is measured by arithmetic calculation of the number of target cells killed during the given reaction. Purified peripheral NK cells from blood are a favored source of effector cells, but unfraction...