[IL-12-induced expression of TRAIL enhances the cytotoxicity of NK cells against Jurkat cells].

AIM: To study the mechanism underlying the IL-12-induced cytotoxic function of NK cells to Jurkat cells. METHODS: NK cells from peripheral blood mononuclear cells (PBMCs) were purified by magnetic sorting and stimulated with or without IL-12. The expression of genes on IL-12-treated and non-IL-12-treated NK cells was analyzed by gene chips and the expression of cytolytic molecules was evaluated by flow cytometry. RESULTS: Seventeen genes were up- (5/17) or down-regulated (12/17) on IL-12-treated NK cells compared with non-IL-12-treated NK cells (fold change≥10). IL-12-induced expression of TRAIL on NK cells mediated the cytotoxicity to Jurkat cells. The expression of TRAIL on subsets of CD56(+);CD16(+); and CD56(-);CD16(+); NK cells significantly increased after the stimulation with IL-12 and Jurkat cells expressed high level of TRAIL receptor 2 (TRAIL-R2). Importantly, the neutralizing mAbs against TRAIL (RIK-2) significantly inhibited the cytotoxicity of NK cells induced by IL-12. CONCLUSION: The expression of TRAIL on human NK cells induced by IL-12 was one of the major mechanisms of cytotoxicity to Jurkat cells.

Phenotypic and functional heterogeneity of natural killer cells from umbilical cord blood mononuclear cells.

Natural killer cells (NK) from umbilical cord blood (CB) play an important role in allogeneic stem cell transplantation and defending infections of newborn. Based on the surface expression of CD56 and CD16 or inhibitory and activatory receptors, NK cells could be subdivided into various subsets with distinct functions. To investigate the biological characterization of NK subsets, the phenotypes and intracellular proteins in freshly isolated CB NK subsets were analyzed at the single cell level by flow cytometry in current study. The production of IFN-gamma and cytotoxicity against K562 target cells were also evaluated after stimulation with IL-12. The results showed that NK cells from CB could be divided into four subsets on the basis of CD56 and CD16 expression. Interestingly, CB NK cells expressed CD45RA but not CD45RO molecules that is similar to the naïve T cells. Moreover, CD27, a memory T cell marker, highly expressed on CD56(hi)CD16- NK cells. The killing-associated molecules, NKG2A, NKG2D, CD95 and the intracellular granzyme B and perforin were heterogeneously expressed among the 4 subsets. Addition of IL-12 into cultures resulted in the induction of IFN-gamma expression by CD56(hi)CD16- and CD56(lo)CD16- subsets and the enhancement of NK cytolytic activity. Taken together, this study elucidated the heterogeneity in phenotypes and biological functions of CB NK cells.

Phenotypically and functionally distinct subsets of natural killer cells in human PBMCs.

Human natural killer (NK) cells are one major component of lymphocytes that mediate early protection against viruses and tumor cells, and play an important role in immune regulatory functions. In this study, we demonstrated that human NK cells could be divided into four subsets, CD56hi CD16(-), CD56lo CD16(-), CD56+CD16+ and CD56(-)CD16+, based on the expression of cell surface CD56 and CD16 molecules. Phenotypic analysis of NK cell subsets indicated that the expression of activation markers, adhesion molecules, memory cell markers, inhibitory and activating receptors, and intracellular proteins (granzyme B and perforin) were heterogeneous. Following interleukin (IL)-2 stimulation, interferon-gamma was preferentially produced by CD56+CD16(-) NK cells and this subset showed more proliferative capacity. The cytolytic activity of both CD56+CD16(-) and CD56+/-CD16+ subsets could be augmented in response to IL-2. The data provided a new definition for NK cell subsets demonstrating their phenotypic and functional diversity and possible stage of NK cell differentiation in peripheral blood.

[Human peripheral blood CD56+ natural killer cell subsets and their phenotypic and biological properties].

OBJECTIVE: To characterize the phenotypic and biological properties of CD56(+) natural killer cells from human peripheral blood mononuclear cells (PBMCs). METHODS: Surface markers and intracellular cytotoxic molecules were stained with multi-color-labeled monoclonal antibodies and analyzed at the single cell level the relation between NK subsets and biological characteristics by flow cytometry. RESULTS: NK cells in PBMCs could be divided into two major populations, CD56(bright) and CD56(dim), based upon the expression of CD56 molecules. Both CD56(bright) and CD56(dim) expressed CD95 (Fas) with CD95(bright) and CD95(dim) subsets. CD56(dim) subsets had higher percentage of CD8, granzyme B and perforin expression compared to those of CD56(bright) subsets. In CD56(bright) and CD56(dim) subpopulations, CD95(bright) and CD8(+) subsets had higher percentage of granzyme B and perforin expression. CONCLUSION: CD56(+) NK cells in PBMCs are composed of distinct subpopulations, CD56(dim) and CD56(dim) CD8(+) NK subsets have higher percentage of granzyme B and perforin and may play an important role in the killing of target cells.