Flow cytometric analysis of cytokine expression in short-term allergen-stimulated T cells mirrors the phenotype of proliferating T cells in long-term cultures.

BACKGROUND: Allergen-specific T(H) cells play an important role in IgE-mediated disorders as allergies. Since this T(H) cell-population only accounts for a small percentage of T(H) cells, they are difficult to phenotype without prior selection or expansion. METHODS: Grass-pollen-specific T(H) cell profiles were evaluated in 5 allergic and 4 non-allergic individuals using three different approaches: CD154 expression on ex vivo grass-pollen-activated PBMCs (i); CFSE-dilution in grass-pollen-restimulated PBMCs (ii) and T cell lines enriched for allergen-specific T cells (iii). RESULTS: Relatively low numbers of allergen-specific T(H) cells were detected using CD154 expression, limiting the power to detect phenotypic differences between allergic and non-allergic individuals. In contrast, higher frequencies of proliferating T(H) cells were detected by loss-of-CFSE intensity in PBMCs and TCLs after grass-pollen-stimulation, resulting in the detection of significantly more IL-4 producing T(H) cells in allergic vs non-allergic individuals. In addition, higher numbers of IFNγ producing T(H) cells were detected in long-term cultures compared to the CD154 expressing T(H) cells. CONCLUSION: To detect allergen-specific T(H) cells for a common allergen as grass-pollen, expansion is not absolutely necessary, although within 8-day grass-pollen cultures, higher numbers of proliferating T(H) cells resulted in increased statistical power to detect phenotypic differences. However, this approach also detects more bystander activated T(H) cells. TCLs resulted in comparable percentages of cytokine expressing T cells as 8-day cultures. Therefore enrichment can be necessary for detection of T(H) cells specific for a single allergen or allergen-derived peptides, but is dispensable for the detection and phenotyping of allergen-specific T(H) cells using crude extracts.

Low-dose acarbose does not delay digestion of starch but reduces its bioavailability.

AIMS: Slowly digestible starch is associated with beneficial health effects. The glucose-lowering drug acarbose has the potential to retard starch digestion since it inhibits alpha-amylase and alpha-glucosidases. We tested the hypothesis that a low dose of acarbose delays the rate of digestion of rapidly digestible starch without reducing its bioavailability and thereby increasing resistant starch flux into the colon. METHODS: In a crossover study, seven healthy males ingested corn pasta (50.3 g dry weight), naturally enriched with (13)C, with and without 12.5 mg acarbose. Plasma glucose and insulin concentrations, and (13)CO(2) and hydrogen excretion in breath were monitored for 6 h after ingestion of the test meals. Using a primed continuous infusion of D-[6,6-(2)H(2)] glucose, the rate of appearance of starch-derived glucose was estimated, reflecting intestinal glucose absorption. RESULTS: Areas under the 2-h postprandial curves of plasma glucose and insulin concentrations were significantly decreased by acarbose (-58.1 +/- 8.2% and -72.7 +/- 7.4%, respectively). Acarbose reduced the overall 6-h appearance of exogenous glucose (bioavailability) by 22 +/- 7% (mean +/-se) and the 6-h cumulative (13)CO(2) excretion by 30 +/- 6%. CONCLUSIONS: These data show that in healthy volunteers a low dose of 12.5 mg acarbose decreases the appearance of starch-derived glucose substantially. Reduced bioavailability seems to contribute to this decrease to a greater extent than delay of digestion. This implies that the treatment effect of acarbose could in part be ascribed to the metabolic effects of colonic starch fermentation.

Influence of a subsequent meal on the oro-cecal transit time of a solid test meal.

BACKGROUND: Oro-cecal transit time (OCTT) is determined for clinical diagnostics of intestinal complaints and research purposes. Ingestion of a subsequent meal during the test period shortens the OCTT of a liquid test meal (glucose solution), as previously reported. This study was conducted to determine whether the same phenomenon occurs after ingestion of a solid test meal. MATERIALS AND METHODS: The OCTT of a pancake was measured with the lactose-[(13)C]-ureide breath test on two occasions in 28 volunteers. All the volunteers took the same subsequent meal once at 4 h and at 6 h after ingestion of the pancake. RESULTS: In 16 of the 56 tests no increase in breath-(13)CO(2) was observed. No statistically significant difference was found between the OCTTs of the test meal after ingestion of the subsequent meal at 4 h or 6 h (367; 311-405 min and 290; 370-405 min, median quartiles, respectively) (P = 0.14, n = 18). Only a subgroup (n = 4) with a short OCTT in the test with the 4-h subsequent meal (278; 259-296 min) tended to have a longer OCTT in the test with the 6-h subsequent meal (390; 379-401 min; P = 0.059). CONCLUSION: The effect of the ingestion of a subsequent meal on the transit time of a test meal is shown to be dependent on the physical form and/or caloric content of the test meal.