Background: Chronic eosinophilic pneumonia (CEP) with asthma precedes the onset of Churg-Strauss syndrome (CSS) in half of all patients with CSS. It is not known what determines whether patients with CEP after asthma will have CSS.
Objective: We examined whether activation of regulatory T cells in patients with CEP inhibits CSS development and is otherwise involved in the mechanism of CSS disease.
Methods: In patients with CSS (n = 38), CEP with asthma (n = 20), and general adult asthma (n = 108), we examined the number of CD4(+)CD25(+) T cells in peripheral blood, as well as levels of expression of the cytokines IL-2, IL-5, IL-10, and TGF-beta by CD4(+)CD25(+) T cells, CD4(+)CD25(-) T cells, or both.
Results: At disease onset, patients with CSS, unlike patients with CEP, had significantly fewer CD4(+)CD25(+) T cells than patients with any step of asthma. CD4(+)CD25(+) T cells producing IL-10 were rarely detected in patients with CSS at disease onset or relapse, whereas the numbers of IL-10-producing T cells in patients with CEP were high at disease onset. There were fewer CD4(+)CD25(-) T cells producing IL-2 in patients with CSS before treatment than in patients with CEP at disease onset. The proportions of CD4(+)CD25(+) T cells producing IL-10 and CD4(+)CD25(-) T cells producing IL-2 in patients with CSS increased at remission.
Conclusions: Maintenance of the numbers of regulatory T cells in patients with CEP with asthma might inhibit CSS development through the action of cytokines, such as IL-10 and IL-2, produced by CD4(+)CD25(+) or CD4(+)CD25(-) T cells. This might be part of a mechanism that influences progression and prognosis in these diseases.