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SUMMARYRecent studies demonstrate in vivo and in vitro cytokine dysregulation in CF epithelial cells. To see if these abnormalities may be generalized to other cells expressing cystic fibrosis transmembrane conductance regulator (CFTR) but not directly exposed to local inflammation, we studied mRNA transcription, intracellular protein production and extracellular secretion of IL-2, IL-4, IL-5, IL-10 and interferon-gamma (IFN-g) from freshly isolated blood mononuclear and CD4 1 T cells from CF patients and controls. Cells were activated by phorbol myristate acetate (PMA) and anti-CD3, PMA±ionomycin, or lipopolysaccharide (LPS) and assessed for cytokine mRNA transcription by semiquantitative reverse transcriptase-polymerase chain reaction, intracellular protein production by flow cytometry, and secretion by supernatant ELISA. Cytokine expression was highly stimulus-dependent. CF cells showed higher IL-10 transcription than control cells after maximal activation by LPS (P 0´01); despite this, cytokine production and secretion were equivalent to controls. CF cells showed lower cellular IL-10 production after PMA-anti-CD3 activation (P 0´002). CF cells secreted less IFN-g than control cells after maximal activation by PMA-anti-CD3 (1836^273 pg/ml versus 9635^3437 pg/ml, P 0´04). IL-2, IL-4 and IL-5 regulation was similar to controls. We conclude that CF mononuclear cells show selective cytokine dysregulation after maximal activation, namely reduced IFN-g secretion and increased IL-10 mRNA without increased production or secretion. These findings extend defects described in respiratory epithelial cells to circulating immunoregulatory cells, suggesting a link between CF genotype and cytokine dysregulation.

Expression of the CFTR protein is thought to be physiologically important only in exocrine epithelial cells. However, chronic respiratory inflammation and infection remain unexplained phenomena in disease pathogenesis. Non‐transformed, antigen‐responsive CD4+ T cells cloned from healthy controls and CF patients homozygous or heterozygous for the δF508 mutation transcribed CFTR mRNA and expressed immunoreactive cytoplasmic CFTR protein. T cell clones (TCC) from controls and CF patients displayed equivalent Ca2+‐mediated Cl− current; however, TCC from patients with CF but not controls displayed defective cAMP‐mediated Cl− current. Although CF‐derived TCC preserved mitogen and antigen proliferative responses and specificity to tetanus toxoid epitopes, they selectively secreted ≈ 45% less IL‐10 compared with control TCC after activation with concanavalin A (Con A) (624 ± 101 versus 1564 ± 401 pg/ml per 106 cells, respectively; P = 0.04) or anti‐CD3/phorbol ester (5148 ± 1634 versus 11 788 ± 2390 pg/ml; P = 0.05). This difference was independent of atopy. Secretion of interferon‐gamma, IL‐2, and IL‐4 was comparable in CF and control TCC after both forms of activation, while IL‐5 was reduced in CF TCC following anti‐CD3/phorbol myristate acetate (PMA) but not after Con A. We conclude that expression of mutant CFTR in human TCC is accompanied by ion channel dysfunction characteristic of the CF phenotype, and is accompanied by a reduction in IL‐10 secretion after polyclonal activation. It is possible that disruption of IL‐10‐mediated anti‐inflammatory homeostasis may contribute to early onset sustained inflammation in CF airways.

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