Lenalidomide-induced CD154 expression on CLL cells is functional. Lenalidomide (L)–treated but not vehicle (VC)–treated CLL B cells induce normal, target B cells to produce antibodies in the presence of PWM. A total of 5 × 10⁴ autologous T cells (AutoTxr) from the healthy target B-cell donor, lenalidomide-treated CLL B cells (L CLLBxr), or vehicle control CLL B cells (VC CLLBxr) were irradiated (20 Gy) and placed in culture with 5 × 10⁴ targets, purified B cells from the healthy donor, in the absence or presence of PWM. Control conditions included 5 × 10⁴ target, unirradiated B cells alone, with and without PWM, and 5 × 10⁴ irradiated and unirradiated CLL B cells, in the absence of target B cells (data not shown). IgM (A) and IgG (B) production was assayed by ELISA from supernatants obtained after 7 days of coculture. (C) A total of 5 × 10⁴ autologous T cells (AutoTxr) from the healthy target B-cell donor, lenalidomide-treated CLL B cells (L CLLBxr), or vehicle control CLL B cells (VC CLLBxr) were irradiated (20 Gy) and placed in culture with 5 × 10⁴ targets, purified B cells from the healthy donor, in the absence or presence of PWM and of a CD40 blocking antibody. Control conditions included 5 × 10⁴ targets, unirradiated B cells alone, with and without PWM, and 5 × 10⁴ irradiated and unirradiated CLL B cells, in the absence of target B cells (data not shown). IgM production was assayed by ELISA from supernatants obtained after 7 days of coculture. Error bars represent SD.