These authors found that the transferred B cells inhibited the in vivo bronchoalveolar lavage (BAL) leukocytosis and eosinophilia associated with allergic airway diseases and that the regulatory effects exerted by these so-called B regulatory (B reg) cells were mediated by TGF-β, as it induced conversion of CD4+CD25− T effector cells into functionally suppressive CD4+CD25+Foxp3+ Treg cells. The gene discussed is CD4; the disease is Increased total leukocyte count.