Simultaneous Targeting of CD3 on T Cells and CD40 on B or Dendritic Cells Augments the Antitumor Reactivity of Tumor-Primed Lymph Node Cells

To date, molecular targets chosen for Ab activation to generate antitumor effector cells have been confined on T cells, such as TCR/CD3, CD28, CD137 (4-1BB), CD134 (OX40), and inducible costimulator. In this report we investigated the immune function of murine tumor-draining lymph node (TDLN) cells after simultaneous Ab targeting of CD3 on T cells and CD40 on APCs. Anti-CD3 plus anti-CD40-activated TDLN cells secreted significantly higher amounts of IFN-γ, but less IL-10, compared with anti-CD3-activated cells. In adoptive immunotherapy, ligation of CD3 and CD40 resulted in the generation of more potent effector cells in mediating tumor regression. Freshly harvested TDLN cells were composed of ∼60% CD3+ T cells, 30–35% CD19+ B cells, 5% CD11c+ dendritic cells (DC), and few CD14+ or NK cells (each <3%). CD40 was distributed predominantly on B cells and DCs. Cell depletion indicated that simultaneous targeting was toward CD3 on T cells and CD40 on APCs, respectively. Elimination of APCs completely abrogated the augmented antitumor responses induced by anti-CD40. Either B cell or DC removal partially, but significantly, reduced the therapeutic efficacy conferred by CD40 engagement. Furthermore, the immunomodulation function of anti-CD40 was associated with its capability to increase IL-12 secretion while inhibiting IL-4 production. Our study establishes a role for CD40 expressed on B cells or DCs in the costimulation of TDLN cells. Eliciting antitumor activity via simultaneous targeting of CD3 on T cells and CD40 on APCs is relevant for the design of effective T cell-based cancer immunotherapy.