Dendritic cells (DCs), professional antigen-presenting cells involved in T cell priming, express CD40, a molecule critical for B cell growth, differentiation, and monocyte activation. This study demonstrates that human dendritic Langerhans cells (D-Lc), generated from cord blood CD34⁺ progenitor cells in the presence of GM-CSF and TNF-α, express functional CD40 at higher levels than B cells. Culturing D-Lc on CD40L-transfected L cells significantly increased their survival and induced morphological changes, including increased dendrite development and altered phenotypic markers. CD40 activation upregulated accessory molecules such as CD58, CD80 (B7-1), and CD86 (B7-2), as well as MHC class II antigens. CD40-activated D-Lc secreted a limited set of cytokines, including TNF-α, IL-8, and MIP-1α, whereas similar activation of monocytes induced a broader range of cytokines. CD40 activation of D-Lc also led to the expression of CD25/Tac, a marker found on interdigitating dendritic cells in secondary lymphoid organs. These findings suggest that CD40 activation of D-Lc mimics physiological interactions between dendritic cells and T cells. The study highlights the functional role of CD40 on dendritic cells, which is essential for their role in T cell activation and immune responses. The results also indicate that CD40 engagement on D-Lc enhances their survival, maturation, and ability to present antigens, contributing to effective immune responses. The study underscores the importance of CD40 in dendritic cell function and its potential implications for immune-related diseases.Dendritic cells (DCs), professional antigen-presenting cells involved in T cell priming, express CD40, a molecule critical for B cell growth, differentiation, and monocyte activation. This study demonstrates that human dendritic Langerhans cells (D-Lc), generated from cord blood CD34⁺ progenitor cells in the presence of GM-CSF and TNF-α, express functional CD40 at higher levels than B cells. Culturing D-Lc on CD40L-transfected L cells significantly increased their survival and induced morphological changes, including increased dendrite development and altered phenotypic markers. CD40 activation upregulated accessory molecules such as CD58, CD80 (B7-1), and CD86 (B7-2), as well as MHC class II antigens. CD40-activated D-Lc secreted a limited set of cytokines, including TNF-α, IL-8, and MIP-1α, whereas similar activation of monocytes induced a broader range of cytokines. CD40 activation of D-Lc also led to the expression of CD25/Tac, a marker found on interdigitating dendritic cells in secondary lymphoid organs. These findings suggest that CD40 activation of D-Lc mimics physiological interactions between dendritic cells and T cells. The study highlights the functional role of CD40 on dendritic cells, which is essential for their role in T cell activation and immune responses. The results also indicate that CD40 engagement on D-Lc enhances their survival, maturation, and ability to present antigens, contributing to effective immune responses. The study underscores the importance of CD40 in dendritic cell function and its potential implications for immune-related diseases.