Ellen C. Ebert

Summary: Human intestinal intraepithelial lymphocytes (IELs), which are T‐cell receptor αβ⁺ CD8⁺ T cells located between epithelial cells (ECs), are likely to participate in the innate immune response against colon cancer. IELs demonstrate spontaneous cytotoxic (SC) activity specifically directed against EC tumours but not against other solid tumour types. The aim of this study was to dissect out the mechanism of SC activity, focusing on the interaction of NKG2D on IELs with its ligands [major histocompatibility complex (MHC) class I chain‐related protein (MIC) and UL16 binding protein (ULBP)] found mainly on EC tumours. A novel series of events occurred. The NKG2D–MIC/ULBP interaction induced Fas ligand (FasL) production and FasL‐mediated SC activity against HT‐29 cells and MIC‐transfectants. Tumour necrosis factor‐α and interferon‐γ, produced independently of this interaction, promoted SC activity. The immune synapse was strengthened by the interaction of CD103 on IELs with E‐cadherin on HT‐29 cells. Neither T‐cell receptor nor MHC class I was involved. While the HT‐29 cells were destroyed by soluble FasL, tumour necrosis factor‐α and interferon‐γ, the IELs were resistant to the effects of these mediators and to FasL expressed by the HT‐29 cells. This unidirectional FasL‐mediated cytotoxicity of IELs against HT‐29 cells, triggered through NKG2D, is unique and is likely to be a property of those CD8⁺ tumour‐infiltrating lymphocytes that phenotypically resemble IELs.

Progressive systemic sclerosis (PSS) causes smooth muscle atrophy and fibrosis of the distal two-thirds of the esophagus. Motility studies show reduced-amplitude or absent peristaltic contractions in this region and normal or decreased lower esophageal sphincter pressure. Patients complain of dysphagia, heartburn, and regurgitation due to reflux and dysmotility. Complications include strictures found in 17% to 29% of patients and Barrett esophagus is 0% to 37%. Candida esophagitis is a complication of PSS not seen with non-PSS reflux. Esophageal disease correlates with pulmonary involvement but not with disease in the stomach or intestines. Whether reflux contributes to the pulmonary disease is an open question. Although manometry is the gold standard for diagnosis, cine-esophagram and scintography are only slightly less sensitive and should be considered for following the patients. Symptoms correlate poorly with evidence of esophagitis or abnormal 24-hour pH recordings. As a result, it is unclear which patients should receive acid-reducing or prokinetic medications and which medication to use. Aspiration precautions are important in those with severe esophageal dysmotility. This review of the literature highlights many areas of uncertainty in the diagnosis and treatment of esophageal disease in PSS that can be addressed in clinical studies.

Summary: Activated T cells that express activation antigens are termed nonprofessional antigen-presenting cells (T-APCs). This study evaluates the ability of lamina propria lymphocytes (LPLs) in inflammatory bowel disease (IBD) to become T-APCs. LPLs were stained by two-colour immunofluorescence to determine the expression of activation antigens on T cells. Those from actively inflamed IBD mucosa expressed greater amounts of MHC class II (DR) and CD86 than did LPL T cells from disease controls or normal individuals. After culture in IL-2 with or without IL-10, the ability of the T-APCs from IBD colon to stimulate allogeneic peripheral blood T cell proliferation was measured. The T-APCs from IBD stimulated an allogeneic mixed lymphocyte reaction, particularly through their expression of DR and CD86, as demonstrated by antibody blocking. Normal LPLs acquired these properties only if repeatedly stimulated with allogeneic peripheral blood lymphocytes (PBLs) used as cell lines in the presence of IL-2. Addition of IL-10 reduced expression of activation antigens and the stimulatory ability of LPLs from either IBD patients or from these cell lines. In summary, LPLs from active IBD, but not from disease controls, express activation antigens that stimulate naïve T cells, a process that is reduced by IL-10. This may contribute to perpetuation of the inflammation.

SUMMARY: Human intraepithelial lymphocytes (IELs) comprise a unique compartment of memory T cell receptor (TCR)-αβ +CD8+ T lymphocytes interspersed between intestinal epithelial cells. They develop potent lymphokine-activated killer (LAK) activity with interleukin (IL)-15, a cytokine that is found in excess in certain mucosal inflammatory states. IL-12, released by activated antigen-presenting cells, is known to potentiate perforin-induced cytotoxicity. This study evaluates the mechanism by which IL-12 up-regulates LAK activity. When IELs were stimulated with IL-15, the CD94+ IEL subset expanded and carried out cytotoxic activity in redirected lysis against P815 cells as well as Fas ligand (FL)- and tumour necrosis factor (TNF)-α-mediated lysis of Jurkat and WEHI cells, respectively. IL-12 enhanced the perforin- and FL-, but not TNF-α-mediated events. In addition, the up-regulated killing of HT-29 cells by IL-12 was reduced by concanamycin (which targets perforin) and antibody neutralizing FL but not by anti-TNF-α antibody. Furthermore, IL-12 augmented IL-15-stimulated release of serine esterases as well as expression of perforin and FL by IELs, but not TNF-α. This study shows that LAK activity, carried out by the CD94+ IELs, involves perforin, FL and TNF-α. IL-12 up-regulates the first two mechanisms of action, showing for the first time its effect on FL production and lytic activity.

SUMMARY: The aim of this study was to examine in detail the low functional capacity of human intraepithelial lymphocytes (IELs) in response to phytohaemagglutinin (PHA) and CD3 ligation. Human IELs were extracted from jejunal mucosa obtained from patients undergoing gastric bypass operations for morbid obesity and compared to peripheral blood (PB) lymphocytes composed predominantly of CD8+ T cells. Calcium influx ([Ca2+]i) was analysed using Fura-2-loaded cells; IL-2 receptor expression was measured by immunofluorescence and flow cytometry; IL-2 binding was determined using radiolabelled IL-2; IL-2 production was quantified by ELISA; and apoptosis was detected with Apo 2·7 staining. Compared to naive PB CD8+ T lymphocytes, calcium influx by IELs was only transient with CD3 ligation and low in amplitude with PHA. IL-2 receptor expression was reduced after CD3 ligation, yet normal in numbers and affinity after PHA stimulation. Both cell types secreted similar amounts of IL-2. CD3 expression on IELs, but not PB CD8+ T cells, declined upon activation, due partly to incomplete reexpression after modulation. Little apoptosis was found. The partial activation of IELs in response to PHA and CD3 ligation, as manifested by diminished [Ca2+]i, resulted in a decline in CD3 expression.