Dominant expression of interleukin 10 but not interferon gamma in CD4(-)CD8(-)alphabetaT cells of autoimmune lymphoproliferative syndrome.

Cytokine expression in CD4-CD8- double-negative (DN) T cells of autoimmune lymphoproliferative syndrome (ALPS) was analysed. Two patients with DN alphabetaT-cell expansion showed higher serum interleukin 10 (IL-10) levels than one patient without it. Intracellular flow-cytometric analysis indicated the IL-10-expressing CD3+CD4-CD8- cells in patients with lymphoproliferation. Quantitative real-time polymerase chain reaction revealed approximately 100 times higher IL-10, but not interferon-gamma or transforming growth factor-beta in DN than in single-positive T cells. IL-10 was exclusively expressed in DN alphabeta but not (gamma)(delta)T cells. Circulating DN alphabetaT cells may constitutively express IL-10 and contribute to the ALPS phenotype.