Murine liver plasmacytoid dendritic cells become potent immunostimulatory cells after Flt-3 ligand expansion

The liver has unique immunological properties. Although dendritic cells (DCs) are central mediators of immune regulation, little is known about liver DCs. Plasmacytoid DCs (pDCs) are a recently identified subtype of murine liver DC. We sought to define the function of freshly isolated murine liver pDCs. We found that normal liver pDCs were weak in stimulating T cells, yet they possessed a proinflammatory cytokine profile with high tumor necrosis factor-alpha and low IL-10 secretion. To facilitate the investigation of murine liver pDCs, we expanded them in vivo with fms-like tyrosine kinase 3 ligand (Flt3L). After Toll-like receptor-9 ligation, expanded liver pDCs secreted high levels of IFN-alpha and were able to stimulate NK cells, NKT cells, and antigen-specific CD8+ T cells in vitro. In addition, Flt3L expansion alone generated pDCs capable of activating antigen-specific CD8+ T cells in vivo.

CONCLUSION

Unstimulated liver pDCs exist in a latent state with the potential to become potent activators of the innate and adaptive immune systems through their interactions with other immune effectors. Our findings have implications for understanding the role of the liver in tolerance and immunity.

Combined stimulation with interleukin-18 and CpG induces murine natural killer dendritic cells to produce IFN-gamma and inhibit tumor growth

Natural killer dendritic cells (NKDC) are a novel subtype of dendritic cells with natural killer (NK) cell properties. IFN-gamma is a pleiotropic cytokine that plays an important role in the innate immune response to tumors. Based on our previous finding that the combination of Toll-like receptor 9 ligand CpG and interleukin (IL)-4 stimulates NKDC to produce IFN-gamma, we hypothesized that NKDC are the major IFN-gamma-producing dendritic cell subtype and may play a significant role in the host antitumor response. We found that under several conditions in vitro and in vivo NKDC accounted for the majority of IFN-gamma production by murine spleen CD11c(+) cells. IL-18 alone induced NKDC to secrete IFN-gamma, and the combination of IL-18 and CpG resulted in a synergistic increase in IFN-gamma production, both in vitro and in vivo. NK cells made 26-fold less IFN-gamma under the same conditions in vitro, whereas dendritic cells produced a negligible amount. The mechanism of IFN-gamma secretion by NKDC depended on IL-12. NKDC selectively proliferated in vitro and in vivo in response to the combination of IL-18 and CpG. Systemic treatment with IL-18 and CpG reduced the number of B16F10 melanoma lung metastases. The mechanism depended on NK1.1(+) cells, as their depletion abrogated the effect. IL-18 and CpG activated NKDC provided greater tumor protection than NK cells in IFN-gamma(-/-) mice. Thus, NKDC are the major dendritic cell subtype to produce IFN-gamma. The combined use of IL-18 and CpG is a viable strategy to potentiate the antitumor function of NKDC.

Biliary obstruction selectively expands and activates liver myeloid dendritic cells

Obstructive jaundice is associated with immunologic derangements and hepatic inflammation and fibrosis. Because dendritic cells (DCs) play a major role in immune regulation, we hypothesized that the immunosuppression associated with jaundice may result from the functional impairment of liver DCs. We found that bile duct ligation (BDL) in mice expanded the myeloid subtype of liver DCs from 20 to 80% of total DCs and increased their absolute number by >15-fold. Liver myeloid DCs following BDL, but not sham laparotomy, had increased Ag uptake in vivo, high IL-6 secretion in response to LPS, and enhanced ability to activate T cells. The effects of BDL were specific to liver DCs, as spleen DCs were not affected. Expansion of liver myeloid DCs depended on Gr-1(+) cells, and we implicated monocyte chemotactic protein-1 as a potential mediator. Thus, obstructive jaundice selectively expands liver myeloid DCs that are highly functional and unlikely to be involved with impaired host immune responses.

In vivo overexpression of Flt3 ligand expands and activates murine spleen natural killer dendritic cells

Natural killer dendritic cells (NKDC) are a unique class of murine immune cells that possess the characteristics of both natural killer (NK) cells and dendritic cells (DC). Because NKDC are able to secrete IFN-gamma, directly lyse tumor cells, and present antigen to naïve T cells, they have immunotherapeutic potential. The relative paucity of NKDC, however, impedes their detailed study. We have found that in vivo, overexpression of the hematopoietic cytokine Flt3 ligand (Flt3L) expands NKDC in various organs from 2-18 fold. Flt3L expanded splenic NKDC retain the ability to lyse tumor cells and become considerably more potent at activating naïve allogeneic and antigen-specific T cells. Compared to normal splenic NKDC, Flt3L-expanded splenic NKDC have a more mature phenotype, a slightly increased ability to capture and process antigen, and a similar cytokine profile. In vivo, we found that Flt3L-expanded splenic NKDC are more effective than normal splenic NKDC in stimulating antigen-specific CD8 T cells. Additionally, we show that NKDC are able to cross-present antigen in vivo. The ability to expand NKDC in vivo using Flt3L will facilitate further analysis of their unique biology. Moreover, Flt3L-expanded NKDC may have enhanced immunotherapeutic potential, given their increased ability to stimulate T cells.

Conventional liver CD4 T cells are functionally distinct and suppressed by environmental factors

The contribution of intrahepatic conventional T cells to the unique immunologic properties of the liver has not been clearly defined. We isolated bulk and CD4 T cells from mouse liver and compared their functions with each other and with their splenic counterparts. Unlike bulk spleen T cells, bulk liver T cells reacted minimally to allogeneic or antigen-loaded syngeneic dendritic cells. However, after exclusion of natural killer T cells (NKTs) and gammadelta T cells by FACS, liver and spleen CD4 T cells actually proliferated to a similar extent upon allogeneic or antigen-specific stimulation. Liver CD4 T cells were more sensitive to interleukin 2 (IL-2) than were spleen CD4 T cells, but had a similar proliferative potential based on their response to CD3 ligation. In addition, activated liver CD4 T cells produced higher levels of IL-4, IL-5, IL-10, and interferon gamma (IFN-gamma) than did splenic CD4 T cells. Therefore, liver CD4 T cells are intrinsically different from spleen CD4 T cells. In vitro, liver or spleen NKTs and gammadelta T cells suppressed liver and spleen CD4 T-cell proliferation in a dose-dependent fashion. In conclusion, unconventional T cells constrain liver CD4 T-cell function. Our findings have implications for pathological conditions of the liver that involve the response of conventional CD4 T lymphocytes.

Laparoscopic treatment of superior mesenteric artery syndrome

BACKGROUND

Superior mesenteric artery syndrome is caused by compression of the third portion of the duodenum by the superior mesenteric artery. Many disease states predispose one to this condition.

METHODS

We present a case report of a young female patient who presented with gastro-duodenal obstruction from superior mesenteric artery syndrome and subsequently underwent surgical treatment with minimally invasive techniques. Pathophysiology of SMA syndrome is reviewed.

RESULTS

The cause of superior mesenteric artery syndrome is variable but always results in duodenal obstruction. Surgery is one treatment option that is effective and can be performed laparoscopically.

CONCLUSION

Laparoscopic duodenojejunostomy is an acceptable method of treating superior mesenteric artery syndrome.

Mini-open rotator cuff repair using a two-row fixation technique: outcomes analysis in patients with small, moderate, and large rotator cuff tears

Mini-open rotator cuff repair has been used successfully to treat small- and moderate-sized rotator cuff tears but not large tears (>3 cm and <5 cm). We use a 2-row fixation technique of repairing the torn cuff to the humerus. We sought to determine if this technique would produce successful results in patients with larger rotator cuff tears. The results of 75 consecutive patients who underwent arthroscopic subacromial decompression with acromioplasty and mini-open rotator cuff repair were evaluated. All patients were evaluated at a minimum 24 months postoperatively (mean, 27 months). All patients were treated with a mini-open rotator cuff repair using a 2-row fixation technique. Patients were evaluated at follow-up with a focused shoulder examination, Hospital for Special Surgery (HSS) Shoulder Questionnaire, and the University of California Los Angeles (UCLA) Shoulder Rating Scale. There were 49 male and 26 female patients, with a mean age of 54 years (range, 34-72 years). All patients failed a preoperative course of physical therapy and nonoperative management. Thirty patients were found to have a large rotator cuff tear (group I), 35 were found to have a moderate-sized tear (group II), and 10 patients had a small tear (group III) at the time of arthroscopy. There was no statistically significant difference in outcome between groups. The mean UCLA Shoulder Rating Scale for all groups was 33.6/35. Mean HSS Shoulder Questionnaire at follow-up was 91%. The mean time from surgery to full recovery was 7 months. Patient's subjective satisfaction based on their preinjury level of performance at most recent follow-up was 92.6%. Eighty-three percent (74/89) of patients returned to their preinjury activity; 93% of patients reported that they would undergo the procedure again. We believe that mini-open rotator cuff repair using a 2-row fixation technique can yield excellent results in patients with small, moderate, and large rotator cuff tears. There was no detectable difference in outcome between groups at 2-year follow-up on clinical evaluation.