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Published on: July 22, 2011
Activation of human intraepithelial lymphocytes reduces CD3 expression
1Department of Medicine, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, NJ, USA.
Insights
Human intraepithelial lymphocytes (IELs) show reduced activation compared to peripheral blood (PB) T cells. This impaired response, seen with phytohaemagglutinin (PHA) and CD3 ligation, affects calcium influx and CD3 expression.
Area of Science:
- Immunology
- Gastroenterology
- Cell Biology
Background:
- Human intraepithelial lymphocytes (IELs) play a crucial role in gut immunity.
- IELs exhibit distinct functional properties compared to peripheral blood (PB) lymphocytes.
- Previous studies suggest IELs have limited responses to common T-cell activation stimuli.
Purpose of the Study:
- To investigate the functional capacity of human IELs in response to phytohaemagglutinin (PHA) and CD3 ligation.
- To compare the activation pathways of IELs with CD8+ T cells from peripheral blood.
- To elucidate the molecular mechanisms underlying IEL hyporesponsiveness.
Main Methods:
- Isolation of IELs from jejunal mucosa and PB lymphocytes.
- Analysis of calcium influx using Fura-2.
- Measurement of IL-2 receptor expression via immunofluorescence and flow cytometry.
- Quantification of IL-2 production using ELISA.
- Detection of apoptosis using Apo 2.7 staining.
Main Results:
- IELs exhibited transient and low-amplitude calcium influx upon CD3 ligation and PHA stimulation, respectively.
- IL-2 receptor expression was reduced post-CD3 ligation but normal after PHA stimulation.
- Both IELs and PB lymphocytes produced similar IL-2 amounts.
- CD3 expression declined on activated IELs, unlike PB CD8+ T cells, due to incomplete reexpression.
Conclusions:
- Human IELs demonstrate partial activation in response to PHA and CD3 ligation.
- Diminished calcium influx and altered CD3 expression contribute to IEL hyporesponsiveness.
- These findings highlight unique activation characteristics of IELs in the intestinal immune system.
Abstract:
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.
