Decreased IL-7 responses in ICL.

<p>(A) Example of pSTAT5 response to IL-7 stimulation measured in whole blood from a healthy donor. The gating strategy to detect pSTAT5 induction by flow cytometry within the memory CD4⁺ T cell population, defined as CD3⁺ CD4⁺ CD45RA⁻ lymphocytes, is depicted. The percentages within the histogram plots indicate the fraction of pSTAT5⁺ cells after high dose IL-7 stimulation. A dose dependent response is observed, with a higher pSTAT5 expression at high IL-7 dose (2 nM) than at low IL-7 dose (20 pM). (B) Example of decreased pSTAT5 response to IL-7 stimulation in memory CD4⁺ T cells from ICL patient P3. (C) Induction of pSTAT5 after stimulation with low dose IL-7. The inducible cytokine response (Δ%pSTAT5⁺) was measured by the difference in the percentage of pSTAT5⁺ cells before and after IL-7 stimulation in memory CD4⁺ T cells. (D) Induction of pSTAT5 after stimulation with high dose IL-7. HD: healthy donors; ICL: patients with idiopathic CD4 lymphocytopenia. P values obtained with the Mann-Whitney U test are reported. (E) Correlation between pSTAT5 responses to high dose IL-7 stimulation and absolute CD4⁺ T cells counts in the blood of ICL patients. (F) Correlation between pSTAT5 responses to high dose IL-7 stimulation and the total lymphocyte count in the blood of ICL patients. The Spearman correlation coefficient R and the corresponding P value are indicated.