Global Unresponsiveness as a Mechanism of Natural Killer Cell Tolerance in Mixed Xenogeneic Chimeras

Mixed xenogeneic chimerism induces T- and B-cell tolerance in mice receiving T-cell-depleted rat bone marrow cells (BMC) following nonmyeloablative conditioning that includes alphabeta and gammadelta T cell and Natural killer (NK) cell-depleting mAbs. NK-cell depletion is essential to permit marrow engraftment, but NK-cell tolerance has not been previously assessed in mixed xenogeneic chimeras. We assessed NK-cell tolerance in rat --> mouse mixed xenogeneic chimeras using in vivo(125)I-5iodo-2-deoxyuridine assays. Additional rapid marrow rejection mechanisms resulted in a requirement for 10-fold more rat than ss2 microglobulin knockout (ss2M(-/-)) (MHC class I-deficient) mouse BMC to achieve engraftment in NK-cell-depleted mice. Both 12-week mixed xenogeneic chimeras and conditioned controls showed reduced resistance to engraftment of ss2M(-/-) mouse and rat BMC. While conditioned control mice recovered NK-cell-mediated resistance to ss2M(-/-) and rat BMC by 16 weeks, mixed chimeras lacked resistance to either, similar to NK-cell-deficient Ly49A transgenic mice. Thus, global NK-cell unresponsiveness is induced by mixed xenogeneic chimerism. Our data suggest that NK-cell anergy is induced by interactions with xenogeneic hematopoietic cells that express activating but not inhibitory ligands for recipient NK cells.     

吸入麻醉对T细胞亚群和NK细胞的影响

观察异氟醚和安氟醚吸入麻醉对病人Ｔ细胞亚群、自然杀伤细胞的影响。方法：３８例行肺叶切除术的病人,随机分为异氟醚麻醉组２０例、安氟醚麻醉组１８例。术前、麻醉后１小时,术后１天、术后１周,术后２周分别检测血清Ｔ细胞亚群及ＮＫ细胞活性。结论安氟醚吸入麻醉对病人细胞免疫的抑制作用较异氟醚吸入麻醉明显。     

Regulatory T Cells Promote Natural Killer Cell Education in Mixed Chimeras

Therapeutic administration of regulatory T cells (Tregs) leads to engraftment of conventional doses of allogeneic bone marrow (BM) in nonirradiated recipient mice conditioned with costimulation blockade and mammalian target of rapamycin inhibition. The mode of action responsible for this Treg effect is poorly understood but may encompass the control of costimulation blockade–resistant natural killer (NK) cells. We show that transient NK cell depletion at the time of BM transplantation led to BM engraftment and persistent chimerism without Treg transfer but failed to induce skin graft tolerance. In contrast, the permanent absence of anti–donor NK reactivity in mice grafted with F1 BM was associated with both chimerism and tolerance comparable to Treg therapy, implying that NK cell tolerization is a critical mechanism of Treg therapy. Indeed, NK cells of Treg‐treated BM recipients reshaped their receptor repertoire in the presence of donor MHC in a manner suggesting attenuated donor reactivity. These results indicate that adoptively transferred Tregs prevent BM rejection, at least in part, by suppressing NK cells and promote tolerance by regulating the appearance of NK cells expressing activating receptors to donor class I MHC.     

Regulatory B Cell‐Dependent Islet Transplant Tolerance Is Also Natural Killer Cell Dependent

Immunologic tolerance to solid organ and islet cell grafts has been achieved in various rodent models by using antibodies directed at CD45RB and Tim‐1. We have shown that this form of tolerance depends on regulatory B cells (Bregs). To elucidate further the mechanism by which Bregs induce tolerance, we investigated the requirement of natural killer (NK) and NKT cells in this model. To do so, hyperglycemic B6, μMT, Beige, or CD1d^?/? mice received BALB/c islet grafts and treatment with the tolerance‐inducing regimen consisting of anti‐CD45RB and anti‐TIM1. B6 mice depleted of both NK and NKT cells by anti‐NK1.1 antibody and mice deficient in NK activity (Beige) did not develop tolerance after dual‐antibody treatment. In contrast, transplant tolerance induction was successful in CD1d^?/? recipients (deficient in NKT cells), indicating that NK, but not NKT, cells are essential in B cell–dependent tolerance. In addition, reconstitution of Beige host with NK cells restored the ability to induce transplant tolerance with dual‐antibody treatment. Transfer of tolerance by B cells from tolerant mice was also dependent on host Nk1.1⁺ cells. In conclusion, these results show that regulatory function of B cells is dependent on NK cells in this model of transplantation tolerance.     

Treg‐Therapy Allows Mixed Chimerism and Transplantation Tolerance Without Cytoreductive Conditioning

Establishment of mixed chimerism through transplantation of allogeneic donor bone marrow (BM) into sufficiently conditioned recipients is an effective experimental approach for the induction of transplantation tolerance. Clinical translation, however, is impeded by the lack of feasible protocols devoid of cytoreductive conditioning (i.e. irradiation and cytotoxic drugs/mAbs). The therapeutic application of regulatory T cells (Tregs) prolongs allograft survival in experimental models, but appears insufficient to induce robust tolerance on its own. We thus investigated whether mixed chimerism and tolerance could be realized without the need for cytoreductive treatment by combining Treg therapy with BM transplantation (BMT). Polyclonal recipient Tregs were cotransplanted with a moderate dose of fully mismatched allogeneic donor BM into recipients conditioned solely with short‐course costimulation blockade and rapamycin. This combination treatment led to long‐term multilineage chimerism and donor‐specific skin graft tolerance. Chimeras also developed humoral and in vitro tolerance. Both deletional and nondeletional mechanisms contributed to maintenance of tolerance. All tested populations of polyclonal Tregs (FoxP3‐transduced Tregs, natural Tregs and TGF‐β induced Tregs) were effective in this setting. Thus, Treg therapy achieves mixed chimerism and tolerance without cytoreductive recipient treatment, thereby eliminating a major toxic element impeding clinical translation of this approach.     

Natural Killer Cell Activity During Premedication, Anaesthesia and Surgery

Natural killer (NK) cell activity of peripheral blood mononuclear cells was measured against K-562 target cells in a 51Cr release assay in eight patients undergoing total hip replacement surgery. Eight consecutive blood samples were taken from each patient. A significant increase of NK cell activity was observed after premedication with diazepam per os. The activity increased further during a combined anaesthesia (thiopentone + N2O + O2 + buprenorphene + pancuronium) and remained increased during surgery. Postoperatively, NK cell activity fell and remained depressed for a period of at least 5 days. The findings of this study indicate that premedication, anaesthesia and surgery cause a rapid and transient increase in NK cell activity, followed by a decline in activity postoperatively. The transient increase in activity may be explained by mobilization of natural killer cells from extravasal space, spleen or lymph nodes into the circulation. The clinical significance of the alterations in NK cell activity is unknown and needs further investigation.     

Depletion of CD8 Memory T Cells for Induction of Tolerance of a Previously Transplanted Kidney Allograft

Heterologous immunologic memory has been considered a potent barrier to tolerance induction in primates. Induction of such tolerance for a previously transplanted organ may be more difficult, because specific memory cells can be induced and activated by a transplanted organ. In the current study, we attempted to induce tolerance to a previously transplanted kidney allograft in nonhuman primates. The conditioning regimen consisted of low dose total body irradiation, thymic irradiation, antithymocyte globulin, and anti‐CD154 antibody followed by a brief course of a calcineurin inhibitor. This regimen had been shown to induce mixed chimerism and allograft tolerance when kidney transplantation (KTx) and donor bone marrow transplantation (DBMT) were simultaneously performed. However, the same regimen failed to induce mixed chimerism when delayed DBMT was performed after KTx. We found that significant levels of memory T cells remained after conditioning, despite effective depletion of naïve T cells. By adding humanized anti‐CD8 monoclonal antibody (cM‐T807), CD8 memory T cells were effectively depleted and these recipients successfully achieved mixed chimerism and tolerance. The current studies provide ‘proof of principle’ that the mixed chimerism approach can induce renal allograft tolerance, even late after organ transplantation if memory T‐cell function is adequately controlled.     

Natural Killer Cell Activity After Open-Heart Surgery

We studied the effects of elective open-heart surgery with cardiopulmonary bypass on peripheral blood natural killer (NK) cell activity in 12 patients with heart disease. Separated mononuclear cells from patients and control cells taken from healthy volunteers were incubated in microtiter plates for 24 h with ³H-thymidine-labelled K 562 cells as target cells. In this test system, higher counts per minute (cpm) values represent a greater number of surviving target cells and thus weaker NK activity. Results of cultures prepared from blood samples taken preoperatively were compared with those taken 2, 7 and 14 days postoperatively. NK cell activity was depressed ( P <0.01) for 2 days after surgery. NK cell activity in the control samples did not change significantly. The results show an impairment of NK cell activity immediately after open-heart surgery.     

Natural Killer Cells and the Immune Response in Solid Organ Transplantation

Natural killer (NK) cells have been characterized classically for their cytotoxicity against pathogen infected or stressed cells as well as for their role in monitoring the expression of self MHC I. However, the participation of NK cells in solid organ transplantation (SOT) is poorly defined due to conflicting clinical and animal model data. Preclinical models have shown that NK cells exacerbate T‐cell allogeneic responses during rejection, but can also promote tolerance induction under immunosuppressive conditions. Further, while protocols such as costimulatory blockade effectively induce tolerance by blocking T‐cell activation and promoting Treg generation, how such regimens regulate other innate and adaptive immune cells, including NK cells, is incomplete. This review examines NK cells and the regulation of their effector functions in SOT.     

Differential Effect of Hemodialysis Membranes on Human Lymphocyte Natural Killer Function

Lymphocytes exposed to cuprammonium cellulose membranes have been shown to exhibit depressed natural killer (NK) function. In the present study we investigated the extent to which three dialyzer membranes of different compositions suppressed human lymphocyte NK activity. Peripheral blood lymphocytes or T cells from normal donors were exposed in vitro to cuprammonium cellulose, cellulose acetate, or polycarbonate dialyzer membranes. After exposure to the membranes, NK activity of the cells was studied by using the NK-sensitive cell line K562 as targets. All three membranes adversely affected human lymphocyte NK function, with cuprammonium cellulose producing the most (70-80%) and polycarbonate producing the least (10-15%) suppression. Our results suggest that the composition of dialyzer membranes affects the extent to which the membranes impair human lymphocyte function. The use of more biocompatible membranes might lessen the potential clinical impact of abnormal NK function in hemodialysis patients.     

Natural Killer Cell Activity in Patients Undergoing Upper Abdominal Surgery: Relationship to the Endocrine Stress Response

Natural killer (NK) cell activity and the endocrine response during and after parietal cell vagotomy were studied in two groups of patients receiving either epidural analgesia extending from S5 to Th4 + general anaesthesia (Group I), or general anaesthesia (Group II). NK cell activity of unseparated mononuclear cells in peripheral blood was measured against K-562 target cells in a 51Cr-release assay. NK cell activity increased in the same way in both groups in relation to premedication, anaesthesia and surgery (P less than 0.01). Postoperatively, the activity fell significantly on the first day (P less than 0.01), but returned to preoperative levels on day 3 (Group I) and day 5 (Group II). The endocrine response measured, except for adrenaline and prolactin, differed between Group I and II. In Group I, plasma noradrenaline and serum cortisol increased insignificantly throughout the observed period--compared to the preoperative level--whereas a significant increase in both hormones was found in Group II during surgery and in the postoperative period. A significant increase in plasma adrenaline and serum prolactin was found in both groups during anaesthesia and surgery. The findings indicate that NK cell activity during upper abdominal surgery is modified in almost the same way during two different anaesthetic techniques, one of which partly seemed to block the endocrine surgical stress response. The fluctuations in NK cell activity were not correlated to the changes measured in hormone concentrations.     

Role of Natural Killer Cell Subsets in Cardiac Allograft Rejection

To achieve donor-specific immune tolerance to allogeneic organ transplants, it is imperative to understand the cell types involved in acute allograft rejection. In wild-type mice, CD4(+) T cells are necessary and sufficient for acute rejection of cardiac allografts. However, when T-cell responses are suboptimal, such as in mice treated with costimulation-targeting agents or in CD28-deficient mice, and perhaps in transplanted patients taking immunosuppressive drugs, the participation of other lymphocytes such as CD8(+) T cells and NK1.1(+) cells becomes apparent. We found that host NK but not NKT cells were required for cardiac rejection. Ly49G2(+) NK cells suppressed rejection, whereas a subset of NK cells lacking inhibitory Ly49 receptors for donor MHC class I molecules was sufficient to promote rejection. Notably, rejection was independent of the activating receptors Ly49D and NKG2D. Finally, our experiments supported a mechanism by which NK cells promote expansion and effector function of alloreactive T cells. Thus, therapies aimed at specific subsets of NK cells may facilitate transplantation tolerance in settings of impaired T-cell function.     

胚胎牌细胞不同移植途径对小鼠接种性肉瘤生长和自然杀伤细胞活性的影响

分别于肌肉、腹腔、周围静脉、门静脉对荷瘤小鼠移植胚胎牌细胞，并于移植后30天、60天分别测定瘤体积抑制率和自然杀伤细胞（NK细胞）活性。结果显示：上述4种移植途径在移植后30天均能明显抑制移植性肿瘤生长，NK细胞活性显著升高（P＜0．01）。但移植后60天，仅门静脉组对肿瘤生长保持良好的抑制状态，NK细胞活性保持较高水平，证明经门静脉移植是牌细胞移植最好的途径。     

胰腺移植免疫耐受研究进展

目的总结胰腺移植免疫耐受的研究进展。方法分析近年来有关胰腺移植免疫耐受研究进展的文献报道。结果外周性耐受及中枢性耐受是诱导免疫耐受的主要方法，其中通过供体特异性骨髓细胞输注诱导嵌合体形成是目前的研究热点。结论供体特异性骨髓细胞输注联合一种或多种外周性耐受方法有望诱导胰腺移植免疫耐受，但需进行深人研究。     

Natural Killer-Like T Cell Lymphoma of the Small Intestine: Report of a Case

We report the case of a 77-year-old Japanese man with natural killer (NK)-like T cell lymphoma of the small intestine diagnosed after an emergency laparotomy for perforated peritonitis. Immunohistochemical staining of the tumor showed that the patient had CD3+ CD8+ CD30− CD56+ CD68− CD79a− UCHL-1+ EMA− LMP-1 NK-like T cell lymphoma. The patient had a history of hepatocellular carcinoma (HCC) and was also diagnosed with T cell non-Hodgkin's lymphoma associated with T cell receptor (TCR) reconstruction in the Jγ chain. Intestinal T cell lymphoma is uncommon and very few cases of CD56+ T cell lymphoma, otherwise known as NK-like T cell lymphoma, have been reported. The patient did not have a history of gluten-sensitive enteropathy (celiac disease). Multiple lesions appeared within months after the initial operation and his condition deteriorated rapidly. We think that this patient probably had NK-type granular lymphocyte-proliferative disorder (NK-GLPD) because the percentage of CD16+ CD56+ cells among peripheral blood mononuclear cells was elevated, at 21%. We report this case to help elucidate the relationship between underlying digestive organ disease and the development of intestinal NK-like T cell lymphoma. An accumulation of other such cases is needed to determine the etiology of this disease.