Several features of chronic lymphocytic leukemia (CLL) suggest that immune-based strategies may have therapeutic potential. A promising approach is provided by the transduction of CLL cells with CD40 ligand (CD40L) by viral vectors to enhance their immunogenicity. We compared the antigen-presenting capacity of CD40L-transduced CLL cells with mock-transduced or CD40L-stimulated CLL cells (CD40-CLL). A significantly higher number of T cells could be expanded using CD40L-transduced CLL cells as antigen-presenting cells (APCs) compared with the control group (P = .008). Using 5 different CLL-associated tumor antigens, including fibromodulin, MDM2 (murine double minute 2), survivin, p53, and KW-13, we show in interferon-gamma (IFN-gamma) enzyme-linked immunospot (ELISPOT) assays after 35 days of in vitro culture that the number of antigen-specific autologous T cells was also significantly higher when CD40L-transduced CLL cells were used as APCs (P < .001). Thus, CD40L-transduced CLL cells are able to induce an antigen-specific T-cell response and might be superior to CD40-CLL cells for immune-based therapeutic strategies in CLL.