Dysregulation of IL-2 and IL-8 production in circulating T lymphocytes from young cystic fibrosis patients

Abstract

It is well documented that patients with cystic fibrosis (CF) are unable to clear persistent airway infections in spite of strong local inflammation, suggesting a dysregulation of immunity in CF. We and others have reported previously that T lymphocytes may play a prominent role in this immune imbalance. In the present work, we compared the reactivity of CD3+ T cells obtained from young CF patients in stable clinical conditions (n = 10, aged 9-16.5 years) to age-matched healthy subjects (n = 6, aged 9-13.5 years). Intracellular levels of interferon (IFN)-gamma, interleukin (IL)-2, IL-8 and IL-10 were determined by flow cytometry after whole blood culture. The data identified T lymphocyte subsets producing either low levels (M1) or high levels (M2) of cytokine under steady-state conditions. We found that the production of IFN-gamma and IL-10 by T lymphocytes was similar between young CF patients and healthy subjects. In contrast, after 4 h of activation with PMA and ionomycin, the percentage of T cells producing high levels of IL-2 (M2) was greater in CF patients (P = 0.02). Moreover, T cells from CF patients produced lower levels of IL-8, before and after activation (P = 0.007). We conclude that a systemic immune imbalance is present in young CF patients, even when clinically stable. This disorder is characterized by the capability of circulating T lymphocytes to produce low levels of IL-8 and by the emergence of more numerous T cells producing high levels of IL-2. This imbalance may contribute to immune dysregulation in CF.

Fig. 1

Consecutive steps in the analysis of single-cell cytokine production in the CD3⁺ T lymphocyte population by flow cytometry after whole blood culture. (a) The complete lymphocyte population was identified on the basis of morphological characteristics. (b) The T cell population was identified by the expression of CD3. (c,d) Verification of T cell activation by expression of CD69 before and after 4 h of activation (respectively) with PMA and ionomycin. (e) Example of intracytoplasmic cytokine (IFN-γ) production by CD3⁺ T cells (blue: before activation, red: after activation), and separation in two cell subsets expressing either low levels (M1) or high levels (M2) of cytokine.

Fig. 2

Flow cytometric analysis of the intracellular expression of IFN-γ (a), IL-2 (b) and IL-8 (c) by the whole CD3⁺ T lymphocyte population. T cells were analysed before and after 4 h of activation with PMA and ionomycin. Results are presented for each CF patient and healthy subject, and show the reactivity of T lymphocytes in regions M1 and M2.