TGF-β increases spontaneous apoptosis of normal peripheral blood B cells after 48 hours in culture. Apoptosis was determined using the TUNEL assay. Representative result from one of seven experiments. (A) Spontaneous apoptosis of normal B cells after 48 hours in culture (control). (B) Apoptosis of B cells with addition of 5 ng/mL TGF-β for 48 hours.