Tumor antigen presentation by epidermal antigen‐presenting cells in the mouse: modulation by granulocyte‐macrophage colony‐stimulating factor, tumor necrosis factor α, and ultraviolet radiation

I‐A+ epidermal antigen‐presenting cells (APCs, Langerhans cells) have been shown to present tumor‐associated antigens (TAAs) and to induce tumor immunity in vivo. This study examined the effects of ultraviolet radiation (UVR) and the cytokines granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) and tumor necrosis factor α (TNF‐α) on the ability of epidermal cells (ECs) to induce or to elicit immunity against the murine spindle cell tumor S1509a. Naive syngeneic mice were immunized three times at weekly intervals with ECs that had been cultured in GM‐CSF for 18 h and then pulsed with TAA derived from S1509a. This resulted in protective immunity against subsequent tumor challenge, providing a model to study the conditions required for sensitization against TAAs by epidermal APCs. Culture of ECs in GM‐CSF was required for induction of significant protective tumor immunity, and UV irradiation or incubation in TNF‐α for 2 h after GM‐CSF incubation abrogated the immunostimulatory effect of GM‐CSF. However, unlike UVR, TNF‐α did not significantly inhibit the induction of immunity when ECs were exposed to TNF‐α before overnight incubation in GM‐CSF, together with GM‐CSF, or after pulsing with TAA, and anti‐TNF‐α antibody treatment did not abrogate the effects of UVR on this system. Furthermore, TNF‐α incubation of ECs augmented their ability to elicit delayed‐type hypersensitivity (DTH) and also enhanced elicitation of DTH by GM‐CSF–cultured ECs, whereas UV‐irradiation reduced it in a dose‐dependent fashion. Taken together, these results demonstrate that GM‐CSF, TNF‐α, and UVR are significant regulators of tumor antigen presentation by epidermal APCs and that the effects of the cytokines examined differ with regard to induction or elicitation of immunity.