Decreased Interleukin 7 Responsiveness of T Lymphocytes in Patients With Idiopathic CD4 Lymphopenia.

Puronen CE, Thompson WL, Imamichi H, Beq S, Hodge JN, Rehm C, Parker R, DerSimonian R, Brenchley JM, Sereti I.
Journal   J Infect Dis.
Analytes Measured  
Matrix Tested   Plasma
Year   2012
Volume   205
Page Numbers   1382-1390
Application   Cytokines and Chemokines
BACKGROUND: Elevated serum interleukin 7 (IL-7) levels are observed in lymphopenic conditions, including idiopathic CD4 lymphopenia (ICL), which is characterized by CD4 lymphopenia in the absence of human immunodeficiency virus infection or other known immunodeficiency.

METHODS: To test whether defective IL-7 signaling could be an etiologic or contributing factor in ICL, peripheral blood mononuclear cells from patients with ICL (median CD4 T-cell count, 160 cells/μL) and healthy controls (median CD4 T-cell count, 582 cells/μL) were evaluated for expression of IL-7Rα chain (CD127) and intracellular phosphorylated STAT-5 (a marker of γc cytokine signaling) after cytokine stimulation. Gene expression was analyzed by real-time polymerase chain reaction following IL-7 stimulation.

RESULTS: The percentage of CD4+CD127+ T cells was lower in patients with ICL, compared with controls (P < .001). Lower levels of STAT-5 phosphorylation after IL-7 stimulation were observed in both CD4 and CD8 T cells from patients with ICL, compared with controls (P < .001 and P = .017, respectively), that inversely correlated in CD4 T cells with serum IL-7 levels (r = -0.734, P = .013). Destabilization of p27(kip1), a critical step for IL-7-induced T-cell cycling, was decreased in patients with ICL, compared with controls (P = .004), after IL-7 stimulation.

CONCLUSIONS: These data suggest that diminished responsiveness to IL-7 in CD4 and CD8 T cells during ICL may be contributing to the dysregulation of T-cell homeostasis.

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