CD4 and neoplasm: However, IL-35 appears to be produced mainly by regulatory T or B cells (Treg or Breg) and epithelial derived tumor cells with a protumor via expanding Tregs and inhibiting CD4+CD25− effector T cells [8], promoting IL-35-producing CD1dhighCD5+ B cells mediated tumor cell proliferation [9], enhancing myeloid cell accumulation [10], and inhibiting tumor cell apoptosis [11, 12].