To investigate why the frequencies of Treg were increased in patients with B-cell NHL, sorted CD4+CD25− cells from patient samples (patients 5, 8, 11, 19, and 27 for BM, n = 5; patients 7 and 24 for involved LN, n = 2) were co-cultured with purified autologous malignant B cells. Here, CD4 is linked to B-cell non-Hodgkin lymphoma.