Mucosal T lymphocytes--peacekeepers and warriors

Orally-administered nanomedicine systems targeting colon inflammation for the treatment of inflammatory bowel disease: latest advances

Inflammatory bowel disease (IBD) is a chronic and idiopathic condition that results in inflammation of the gastrointestinal tract, leading to conditions such as ulcerative colitis and Crohn's disease. Commonly used treatments for IBD include anti-inflammatory drugs, immunosuppressants, and antibiotics. Fecal microbiota transplantation is also being explored as a potential treatment method; however, these drugs may lead to systemic side effects. Oral administration is preferred for IBD treatment, but accurately locating the inflamed area in the colon is challenging due to multiple physiological barriers. Nanoparticle drug delivery systems possess unique physicochemical properties that enable precise delivery to the target site for IBD treatment, exploiting the increased permeability and retention effect of inflamed intestines. The first part of this review comprehensively introduces the pathophysiological environment of IBD, covering the gastrointestinal pH, various enzymes in the pathway, transport time, intestinal mucus, intestinal epithelium, intestinal immune cells, and intestinal microbiota. The second part focuses on the latest advances in the mechanism and strategies of targeted delivery using oral nanoparticle drug delivery systems for colitis-related fields. Finally, we present challenges and potential directions for future IBD treatment with the assistance of nanotechnology.

Effect of alemtuzumab on intestinal intraepithelial lymphocytes and intestinal barrier function in cynomolgus model

Background:

Alemtuzumab has been used in organ transplantation and a variety of hematologic malignancies (especially for the treatment of B-cell chronic lymphocytic leukemia). However, serious infectious complications frequently occur after treatment. The reason for increased infections postalemtuzumab treatment is unknown at this stage. We explore the effect of alemtuzumab on intestinal intraepithelial lymphocytes (IELs) and intestinal barrier function in cynomolgus model to explain the reason of infection following alemtuzumab treatment.

Methods:

Twelve male cynomolguses were randomly assigned to either a treatment or control group. The treatment group received alemtuzumab (3 mg/kg, intravenous injection) while the control group received the same volume of physiological saline. Intestinal IELs were isolated from the control group and the treatment group (on day 9, 35, and 70 after treatment) for counting and flow cytometric analysis. Moreover, intestinal permeability was monitored by enzymatic spectrophotometric technique and enzyme-linked immunosorbent assay.

Results:

The numbers of IELs were decreased significantly on day 9 after treatment compared with the control group (0.35 ± 0.07 × 10⁸ and 1.35 ± 0.09 × 10⁸, respectively; P < 0.05) and were not fully restored until day 70 after treatment. There were significant differences among four groups considering IELs subtypes. In addition, the proportion of apoptotic IELs after alemtuzumab treatment was significantly higher than in the control group (22.01 ± 3.67 and 6.01 ± 1.42, respectively; P < 0.05). Moreover, the concentration of D-lactate and endotoxin was also increased significantly on day 9 after treatment.

Conclusions:

Alemtuzumab treatment depletes lymphocytes in the peripheral blood and intestine of cynomolgus model. The induction of apoptosis is an important mechanism of lymphocyte depletion after alemtuzumab treatment. Notably, intestinal barrier function may be disrupted after alemtuzumab treatment.

Natural killer cell receptor T-lymphocytes in normal and Helicobacter pylori-infected human gastric mucosa

BACKGROUND

Helicobacter pylori infection is associated with development of chronic inflammation and infiltration of immune cells into the gastric mucosa. As unconventional T-lymphocytes expressing natural killer cell receptors are considered to play central roles in the immune response against infection, a study investigating their frequencies in normal and H. pylori-infected gastric mucosa was undertaken.

MATERIALS AND METHODS

Flow cytometry was used to quantify T-cells expressing the natural killer cell markers CD161, CD56, and CD94 in freshly isolated lymphocytes from the epithelial and lamina propria layers of gastric mucosa. Thirteen H. pylori-positive and 24 H. pylori-negative individuals were studied.

RESULTS

CD94(+) T-cells were the most abundant (up to 40%) natural killer receptor-positive T-cell population in epithelial and lamina propria layers of H. pylori-negative gastric mucosa. CD161(+) T-cells accounted for about one-third of all T-cells in both compartments, but the lowest proportion were of CD56(+) T-cells. Compared with H. pylori-negative mucosa, in H. pylori-infected mucosa the numbers of CD161(+) T-cells were significantly greater (p = .04) in the epithelium, whereas the numbers of CD56(+) T-cells were lower (p = .01) in the lamina propria. A minor population (< 2%) of T-cells in both mucosal layers of H. pylori-negative subjects were natural killer T-cells, and whose proportions were not significantly different (p > .05) to those in H. pylori-infected individuals.

CONCLUSIONS

The predominance, heterogeneity, and distribution of natural killer cell receptor-positive T-cells at different locations within the gastric mucosa reflects a potential functional role during H. pylori infection and warrants further investigation.

Gammadelta T lymphocytes: a new type of regulatory T cells suppressing murine 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced colitis

BACKGROUND

The intestinal immune system is continuously challenged by antigen without becoming dysregulated. However, injury of the mucosa by, i.e. dextran sulphate sodium causes severe inflammation in gammadelta T-cell-deficient mice. We therefore asked whether gammadelta T cells have regulatory functions.

MATERIALS AND METHODS

gammadelta T cells were isolated from spleens and mesenteric lymph nodes of C57BL/6 wild-type (wt) mice. Proliferation and cytokine secretion of gammadelta T cells were quantified by [(3)H] thymidine incorporation and ELISA. Additionally, proliferation of carboxyfluorescein diacetate succinimidylester-labelled CD4(+) T cells cocultured with gammadelta T cells was analysed by flow cytometry. Finally, gammadelta T cells from wt or interleukin-10 transgenic (IL-10tg) mice were transferred into congenic mice with 2,4,6-trinitrobenzene sulphonic acid (TNBS)-induced colitis.

RESULTS

gammadelta T cells were hyporesponsive to CD3/CD28 stimulation and suppressed CD4(+) T-cell proliferation (up to 66+/-7% suppression) in vitro. Further, the preventive transfer of wt or IL-10tg gammadelta T cells ameliorated TNBS-induced colitis resulting in prolonged survival and reduced histological damage (1.5+/-0.4 and 1.3+/-0.2, respectively vs. 3.8+/-0.3 in untransferred mice, p<0.05). This was accompanied by reduced TNF-alpha and increased IL-10 and TGF-beta secretion from intestinal and splenic lymphocytes.

CONCLUSIONS

Murine gammadelta T cells are a new type of regulatory T cells in vitro and act protective on mouse TNBS-induced colitis in vivo. Future studies have to define the underlying mechanism and to investigate whether gammadelta T cells can be used for immunotherapy of human inflammatory bowel disease.

Cutting Edge: Distinct NK receptor profiles are imprinted on CD8 T cells in the mucosa and periphery during the same antigen challenge: role of tissue-specific factors

NK cell receptors (NKRs) modulate T lymphocyte responses by modifying the Ag activation threshold. However, what governs their expression on T cells remains unclear. In this study we show that different NKRs are imprinted on CD8 T cells in the gut mucosa and periphery during the same Ag challenge. After a viral, bacterial, and tumor challenge, most CD8 peritoneal exudate lymphocytes expressed NKG2A but not 2B4. In contrast, most CD8 intraepithelial lymphocytes exhibited 2B4 but not NKG2A. Our data suggest that tissue-specific factors may determine the pattern of NKR expression. In the gut, CD70 licensing appears to promote 2B4 induction on mucosal CD8 T cells. Conversely, retinoic acid produced by the intestinal dendritic cells may suppress NKG2A expression. Thus, tissue-specific factors regulate NKR expression and may confer T cells with differing effector functions in a tissue and site-specific manner.

Intramuscular rather than oral administration of replication-defective adenoviral vaccine vector induces specific CD8+ T cell responses in the gut

Gut-associated lymphoid tissue (GALT) is the primary replication site for HIV-1, resulting in a pronounced CD4(+) T cell loss in this tissue during primary infection. A mucosal vaccine that generates HIV-specific CD8(+) T cells in the gut could prevent the establishment of founder populations and broadcasting of virus. Here, we immunized mice orally and systemically with a chimpanzee derived adenoviral vector expressing HIV gag (AdC68gag) and measured frequencies of gag-specific interferon-gamma (IFN-gamma) producing CD8(+) T cells in the GALT. A single oral administration was inefficient at eliciting responses in the mesenteric lymph nodes and Peyer's Patches, while a single intramuscular administration elicited strong systemic and detectable mucosal responses. The gag-specific CD8(+) T cell responses were present in both acute and memory phases following intramuscular administration.