To further determine whether human TRAPs (hTRAPs) could induce human CD4+ T cells to produce IL-6, we collected hTRAPs from the culture media of 3 human tumor cell lines, A375, MDA-MB-231 and HepG2, and from the malignant effusions or ascites of 8 cancer patients (Additional file 1: Table S1). Here, CD4 is linked to cancer.