Quantitative and functional characteristics of intestinal-homing memory T cells: analysis of Crohn's disease patients and healthy controls

Abstract

Circulating memory T cells can be subdivided on the basis of beta7 integrin expression. The beta7+ population contains cells primed in the intestine capable of homing back to the gut. We hypothesized that cytokine production by beta7+ memory T cells reflects the specialized mucosal compartment in which they were primed. Flow cytometry of whole blood was used to assess numbers of beta7+ (beta7hi and beta7int) and beta7- memory T cells and their production of Th1 and regulatory cytokines in healthy controls and Crohn's disease patients. In controls, beta7+ and beta7- memory T cells displayed a similar qualitative profile of cytokine production but the beta7+ population was enriched for cytokine-producing effector cells. In addition, the beta7hi population contained more cytokine-producing cells than the beta7int population, suggesting a gradient of cytokine production based on beta7 integrin expression. In active Crohn's disease, there was altered expression of beta7 integrin with a decrease in intestinal-homing memory T cells and an increase in systemic memory T cells. Furthermore, there was a selective loss of IL-10 and increase in TGF-beta in both beta7+ and beta7- memory T cell subsets which may contribute to the pathogenesis of the inflammatory process in Crohn's disease.

Fig. 1

Expression of β7 integrin and CD45RA on CD3⁺ cells. CD3⁺ cells from a representative control consist of CD45RA⁺ (naive) and CD45RA⁻ (memory) cells. The CD45RA− memory cells were further divided based on their β7 integrin expression into β7^hi, β7^int and β7^– subsets as shown. Interferon-γ (IFN-γ) production was determined for β7^hi, β7^int and β7⁻ subsets and CD45RA⁺ cells using Enhanced Normalized Subtraction (ENS). The percentage represents the proportion of cells staining positive for cytokine.

Fig. 2

Cytokine production by β7⁺ memory T cells, β7^– memory T cells and naive T cells from healthy controls. Production of the cytokines IL-10 (a), IFN-γ (b), TNF-α (c), IL-2 (d) and TGF-β (e) was measured by intracellular cytokine staining after 4 h stimulation with PMA and ionomycin. Production of the cytokines was assessed for each of the following cell-populations: β7⁺ memory T cells, β7^– memory T cells and naive T cells.

Fig. 3

Absolute numbers of circulating CD3⁺ cells in controls and patients with Crohn's disease (a). Proportion (b) and absolute number (c) of circulating CD45RA⁺ naive T cells in controls and patients with Crohn's disease. Proportion (d) and absolute number (e) of circulating CD45RA⁻ memory T cells in controls and patients with Crohn's disease.

Fig. 4

Ratio of β7⁺ to β7^– CD45RA^– memory T cells in controls and Crohn's disease patients (a). Proportion (b) and absolute number (c) of circulating β7^– and β7⁺ CD45RA_- memory T cells in controls and patients with Crohn's disease. Further division of the β7⁺ population into β7^hi and β7^int populations was performed and the proportion (d) and absolute number (e) of β7^hi and β7^int circulating CD45RA⁻ memory T cells in controls and patients with Crohn's disease was calculated.

Fig. 5

Cytokine production by β7⁺ and β7^– circulating memory T cells from controls and patients with Crohn's disease. Production of the cytokines IL-10 (a), IFN-γ (b), TNF-α (c), IL-2 (d) and TGF (e) was assessed by intracellular cytokine staining after 4 h stimulation with PMA and ionomycin.