Tae Jin Kim

Novel streptavidin-functionalized silicon nanowire arrays for CD4 + T lymphocyte separation

Silicon nanowires (SiNWs) offer promising inorganic nanostructures for biomedical application. Here, we report the development of a novel SiNW array designed for isolating primary CD4(+) T lymphocytes from the heterogeneous mixture of cell populations. Our system employed the specific high-affinity binding features of streptavidin (STR)-functionalized SiNW with biotin-labeled CD4(+) T lymphocytes. Fabricated SiNW arrays easily separated the CD4(+) T lymphocytes from the mouse whole splenocytes with over approximately 88% purity and demonstrated tight attachment to CD4(+) T lymphocytes by scanning electron microscopy. Thus, our STR-SiNW arrays provide a potential tool for specific cell separation and further present a possibility to be applied to the other area of biomedical applications.

Decreased expression of DNA repair proteins Ku70 and Mre11 is associated with aging and may contribute to the cellular senescence.

The gradual loss of telomeric DNA can contribute to replicative senescence and thus, having longer telomeric DNA is generally considered to provide a longer lifespan. Maintenance and stabilization of telomeric DNA is assisted by binding of multiple DNA-binding proteins, including those involved in double strand break (DSB) repair. We reasoned that declining DSB repair capacity and increased telomere shortening in aged individuals may be associated with decreased expression of DSB repair proteins capable of telomere binding. Our data presented here show that among the DSB repair proteins tested, only the expression of Ku70 and Mre11 showed statistically significant age-dependent changes in human lymphocytes. Furthermore, we found that expressions of Ku70 and Mre11 are statistically correlated, which indicate that the function of Ku70 and Mre11 may be related. All the other DSB repair proteins tested, Sir2, TRF1 and Ku80, did not show any significant differences upon aging. In line with these data, people who live in the regional community (longevity group), which was found to have statistically longer average life span than the rest area, shows higher level of Ku70 expression than those living in the neighboring control community. Taken together, our data show, for the first time, that Ku70 and Mre11 may represent new biomarkers for aging and further suggest that maintenance of higher expression of Ku70 and Mre11 may be responsible for keeping longer life span observed in the longevity group.

Cellular and Molecular Changes Associated With Inhibitory Effect of Pioglitazone on Neointimal Growth in Patients With Type 2 Diabetes After Zotarolimus-Eluting Stent Implantation

Objective—To investigate the mechanistic basis underlying antirestenosis and the antiatherogenic effect of pioglitazone in patients with type 2 diabetes mellitus who were undergoing zotarolimus-eluting stent implantation. Methods and Results—Recent studies highlight the beneficial effect of pioglitazone in attenuating neointimal growth after stent implantation. Patients with coronary artery diseases were randomly assigned to pioglitazone (n=47) or placebo (n=47) after stent implantation. Pioglitazone significantly reduced neointimal hyperplasia within the stented lesion and attenuated total plaque burden in the in-segment regions of the stent, as assessed by intravascular ultrasonography at the 8-month follow-up. These changes were preceded by reduced circulating natural killer (NK) cells, diminished interleukin 6 and monocyte chemoattractant protein-1 levels, and downregulation of chemokine receptor 2 at 2 days after stent implantation; and an elevated interleukin 10 level at 10 days after implantation. Furthermore, the proliferation and migration of vascular smooth muscle cells were inhibited in the presence of pioglitazone-treated patient serum, demonstrating that the antiproliferative effects of pioglitazone occurred concurrently with its antiinflammatory action. Conclusion—Our data present early cellular and immunologic changes by pioglitazone that might have been associated with antirestenotic and antiatherogenic effects in diabetic patients. Inhibiting proinflammatory responses while promoting antiinflammatory circuits, together with an antiproliferative action, may, in part, account for the antirestenotic effect of pioglitazone by altering vascular remodeling processes in the early phase.

FK506 causes cellular and functional defects in human natural killer cells

The role of NK cells in allogeneic HCT has been increasingly appreciated, particularly in the GVL effect. Although FK506 has been used widely to prevent GVHD, its action was considered to be primarily through activated T cells. In this study, we provide direct evidence for the first time that human NK cells are immediate targets of FK506. Our in vivo data from patients undergoing peripheral blood stem cell transplantation or BMT showed a reduced number of NK cells with down‐regulated CD25 expression in their peripheral blood compartment. Likewise, FK506 caused profound inhibition of NK cell proliferation in vitro and suppressed NK cytotoxicity and cytokine secretion in response to IL‐2. These defects were accompanied by impaired cell clustering and selective down‐regulation of adhesion molecules, ICAM‐1, CD2, CD49d, and CD58. Furthermore, FK506 specifically inhibited expression of NKG2D, CD48, and DNAM1 receptors without affecting that of 2B4, NKp30, NKp44, and NKp46. As a result, natural cytotoxicity against K562 tumor targets was impaired, while leaving redirected ADCC via 2B4 intact. Finally, FK506‐treated NK cells showed impaired IL‐2R signaling and inhibition of STAT3. Collectively, these signaling impairments and selective down‐regulation of NK receptors by FK506 may underlie the proliferative and functional defects of NK cells. Thus, our data provide a new insight into the mechanism of immunosuppression by FK506, which should be considered to interpret the outcome of graft transplantation.

Homotypic cell to cell cross-talk among human natural killer cells reveals differential and overlapping roles of 2B4 and CD2.

Human natural killer (NK) cells express an abundant level of 2B4 and CD2 on their surface. Their counter-receptors, CD48 and CD58, are also expressed on the NK cell surface, raising a question about the functional consequences of potential 2B4/CD48 and CD2/CD58 interactions. Using blocking antibodies specific to each receptor, we demonstrated that both 2B4/CD48 and CD2/CD58 interactions were essential for the development of NK effector functions: cytotoxicity and cytokine secretion. However, only 2B4/CD48, but not CD2/CD58, interactions were shown to be critical for the optimal NK cell proliferation in response to interleukin (IL)-2. IL-2-activated NK cells cultured in the absence of 2B4/CD48 or CD2/CD58 interactions were severely impaired for their ability to induce intracellular calcium mobilization and subsequent ERK activation upon tumor target exposure, suggesting that the early signaling pathway of NK receptors leading to impaired cytolysis and interferon (IFN)-γ secretion was inhibited. Nevertheless, these defects did not fully account for the reduced proliferation of NK cells in the absence of 2B4/CD48 interactions, because anti-CD2 or anti-CD58 monoclonal antibody (mAb)-treated NK cells, showing defective signaling and effector functions, displayed normal proliferation upon IL-2 stimulation. These results propose the signaling divergence between pathways leading to cell proliferation and cytotoxicity/cytokine release, which can be differentially regulated by 2B4 and CD2 during IL-2-driven NK cell activation. Collectively, these results reveal the importance of homotypic NK-to-NK cell cross-talk through 2B4/CD48 and CD2/CD58 pairs and further present their differential and overlapping roles in human NK cells.

Upregulation of Fas and downregulation of CD94?NKG2A inhibitory receptors on circulating natural killer cells in patients with new-onset psoriasis

Backgroundu2002 Psoriasis has been considered as a T‐helper 1 cell‐mediated autoimmune disease driven by collaboration with multiple components of innate and acquired immune cells. Natural killer (NK) cells have been shown to bridge innate and acquired immunity, and thus could potentially contribute to the pathophysiology of psoriasis.

Homotypic NK cell-to-cell communication controls cytokine responsiveness of innate immune NK cells

While stationary organ cells are in continuous contact with neighboring cells, immune cells circulate throughout the body without an apparent requirement for cell-cell contact to persist in vivo. This study challenges current convention by demonstrating, both in vitro and in vivo, that innate immune NK cells can engage in homotypic NK-to-NK cell interactions for optimal survival, activation, and proliferation. Using a specialized cell-laden microwell approach, we discover that NK cells experiencing constant NK-to-NK contact exhibit a synergistic increase in activation status, cell proliferation, and anti-tumor function in response to IL-2 or IL-15. This effect is dependent on 2B4/CD48 ligation and an active cytoskeleton, resulting in amplification of IL-2 receptor signaling, enhanced CD122/CD132 colocalization, CD25 upregulation, and Stat3 activation. Conversely, ‘orphan NK cells demonstrate no such synergy and fail to persist. Therefore, our data uncover the existence of homotypic cell-to-cell communication among mobile innate lymphocytes, which promotes functional synergy within the cytokine-rich microenvironment.

Augmentation of natural cytotoxicity by chronic low-dose ionizing radiation in murine natural killer cells primed by IL-2

The possible beneficial effects of chronic low-dose irradiation (LDR) and its mechanism of action in a variety of pathophysiological processes such as cancer are a subject of intense investigation. While animal studies involving long-term exposure to LDR have yielded encouraging results, the influence of LDR at the cellular level has been less well defined. We reasoned that since natural killer (NK) cells constitute an early responder to exogenous stress, NK cells may reveal sentinel alterations in function upon exposure to LDR. When purified NK cells received LDR at 4.2 mGy/h for a total of 0.2 Gy in vitro, no significant difference in cell viability was observed. Likewise, no functional changes were detected in LDR-exposed NK cells, demonstrating that LDR alone was insufficient to generate changes at the cellular level. Nonetheless, significant augmentation of cytotoxic, but not proliferative, function was detected when NK cells were stimulated with low-dose IL-2 prior to irradiation. This enhancement of NK cytotoxicity was not due to alterations in NK-activating receptors, NK1.1, NKG2D, CD69 and 2B4, or changes in the rate of early or late apoptosis. Therefore, LDR, in the presence of suboptimal cytokine levels, can facilitate anti-tumor cytotoxicity of NK cells without influencing cellular proliferation or apoptosis. Whether these results translate to in vivo consequences remains to be seen; however, our data provide initial evidence that exposure to LDR can lead to subtle immune-enhancing effects on NK cells and may explain, in part, the functional basis underlying, diverse beneficial effects seen in the animals chronically exposed to LDR.

The nuclear 16-kD protein methylation increases in the early period of liver regeneration in a hepatectomized rat.

Methylation events play a critical role in various cellular processes including regulation of gene transcription and proliferation. We observed that methyltransferase activity underwent time-dependent changes in the cytosol of the rat hepatocytes upon partial hepatectomy. However, any change in the methylation of nuclear proteins is not clear during hepatocyte proliferation. The nuclear fraction possesses basal level of methyltransferase to catalyze methylation of several proteins ranging from 7 to 70 kD prior to any hepatecmony. The specific p16 (16 kD) band was transiently and heavily methylated post 1 day hepatectomy, and then became non- detectable, but not in the control liver. Methylation of p16 band was completely inhibited by exogenously added histones, particularly 2AS, 1, 2A and 2B subtypes. The methylated p16 protein remains stable in either acid or alkali- induced demethylation conditions, indicating that methylation is not likely to occur on isoaspartyl or C-terminal cysteinyl residues. Exogenous addition of non-hydrolyzable GTP caused a dose- dependent suppression of a p16 methylation suggesting that G-proteins might play a role as an endogenous methylation inhibitor in vivo. Taken together, we have identified the proliferation event associated-methylation of the nuclear p16 protein in the hepatocytes undergoing liver regeneration.

Single Step Isolation and Activation of Primary CD3+ T Lymphocytes Using Alcohol-Dispersed Electrospun Magnetic Nanofibers

Electrospun polymer nanofibers with entrapped magnetic nanoparticles (magnetic NP-NF) represent a novel scaffold substrate that can be functionalized for single-step isolation and activation of specific lymphocyte subsets. Using a surface-embedded T cell receptor ligand/trigger (anti-CD3 monoclonal antibody), we demonstrate, as proof of principle, the use of magnetic NP-NF to specifically isolate, enrich, and activate CD3(+) T cells from a heterogeneous cell mixture, leading to preferential expansion of CD8(+)CD3(+) T cells. The large surface area, adjustable antibody density, and embedded paramagnetic properties of the NP-NF permitted enhanced activation and expansion; its use represents a strategy that is amenable to an efficient selection process for adoptive cellular therapy as well as for the isolation of other cellular subsets for downstream translational applications.