CD4+CD25+ regulatory T cells play a major role in controlling inflammatory responses. In this study, we examined whether T regulatory cells might be deficient in AD.

CD4+CD25+ and CD4+CD25- T cells were isolated from peripheral blood mononuclear cells (PBMC) using immunomagnetic beads. Cells were cultured with 0.5 ug/ml anti-CD3 or superantigen, 100ng/ml staphylococcal enterotoxin B (SEB), for 72 hours. Proliferation was measured by [3H]-thymidine incorporation. CD4, CD8, CD25 and CLA expression on PBMC was assessed by flow cytometry.

Surprisingly, CD4+CD25+ cells were significantly (p<0.014) elevated in AD (6.68%, n=15) but not asthma patients (3.41%, n=12) or non-atopic normal control subjects (3.34%, n=14). Expression of CD25+ was higher in CD4+CLA+ cell population than CD4+CLA- cell population in all groups (p<0.0001). AD patients also had higher expression of CD25+ in CD4+CLA+ cells than asthma patients and non-atopic subjects with values 35.95% vs 22.44% vs 23.03%, respectively (p<0.005). CD4+CD25+ cells were anergic to anti-CD3 stimulation. When CD4+CD25+ cells were mixed with CD4+CD25- cells, proliferation was suppressed in all groups following anti-CD3 stimulation. In contrast, after SEB stimulation, CD4+CD25+ cells were no longer anergic and demonstrated proliferation. Furthermore, when CD4+CD25+ cells were mixed with CD4+CD25- cells and stimulated with SEB, the suppressive function of T regulatory cells disappeared.

AD patients had significantly increased numbers of peripheral blood T regulatory cells with normal immunosuppressive activity. However following superantigen stimulation, T regulatory cells lost their immunosuppressive activity suggesting a novel mechanism by which superantigens augment T cell activation in AD.