Defect of regulatory T cells in patients with Omenn syndrome

Phenotype of FOXP3⁺ Treg cells in patients (Pt) with OS. A, PBMCs from 4 patients with OS and 2 representative age-matched HDs were stained with anti-CD4, anti-CD25, and anti-FOXP3 mAbs. Results shown are gated on the CD4⁺ T cells. Quadrant markers were set based on staining with isotype control mAbs and numbers indicate the percentage of each subset within the CD4⁺ population. B, Absolute counts of circulating CD4⁺ FOXP3⁺ cells. C, Activation status of CD4⁺ FOXP3⁺ cells. The percentages of CD4⁺ FOXP3⁺ cells expressing CD25, CD45RA, HLA-DR, and CCR7 markers are reported. ∗∗P < .01.

Suppressive activity of patients' CD4⁺ CD25^high Treg cells. The ability of freshly isolated CD4⁺CD25^high CD127^low/– Treg cells from patients with OS and HDs to suppress proliferation of either autologous (A) or allogeneic (B) CD4⁺CD25^–CD127⁺ responder T cells was assessed. Treg cells were added to activated responder cells (R) at 0.5:1 ratio, and proliferation was evaluated by [³H]thymidine incorporation (see Methods for details). In parallel, the IFN-γ secretion was measured in culture supernatants. Percentages indicate inhibition of proliferation or cytokine secretion (average ± SD in case multiple experiments testing different HDs).

Histopathologic features and FOXP3 expression in the lymph nodes of patients with OS. Inguinal lymph nodes sections from an HD showed numerous FOXP3⁺ cells distributed within the T-cell areas (A). In contrast, lymph nodes sections from 2 representative biopsies from patients with OS revealed either a reduced number of FOXP3⁺ cells in the lymph nodes showing nondepleted features (patient 4; B) or a dramatic depletion of FOXP3⁺ cells in the lymph nodes with a depleted histopathologic pattern (patient 1; C). FOXP3⁺ cells, brown nuclear staining. All panels, original magnification ×20.

Histopathologic features and FOXP3 expression in the thymus of a patient with OS. Thymus sections from an HD showed numerous FOXP3⁺ cells distributed within the thymic medulla near the Hassall bodies (Hb; A). The thymic biopsy of the patient with OS (patient 5; B) did not show any evidence of FOXP3 protein expression. Real-time PCR analysis of cDNA prepared from RNA isolated from normal thymus and thymus of the same patient with OS confirmed the depletion of FOXP3 expression in OS (C). FOXP3 mRNA was undetectable in the patient with severe combined immunodeficiency (SCID). The level of FOXP3 mRNA, normalized for the expression level of GAPDH, was plotted as fold increase over those in the control. FOXP3⁺ cells, brown nuclear staining; A and B, original magnification ×20.