Fig. 2.

Potential mechanisms explaining how sIL-2R might contribute to the immunopathology of sarcoidosis. A) Binding of sIL-2R to IL-2 increases the affinity of IL-2 for the intermediate affinity receptor. Consequently, the sIL-2R-IL-2 complex can activate resting (potentially autoreactive) T cells, which then proliferate. B) Binding of sIL-2R to IL-2 sequesters IL-2 from resting cells only expressing the intermediate affinity receptor. As a result, T cell proliferation is reduced and antigen clearance is affected. (s)IL-2Rα: red; IL-2Rβ: purple; IL-2Rγ: blue; IL-2: purple sphere