SUPERNATANTS FROM UVB RADIATION-EXPOSED KERATINOCYTES INHIBIT LANGERHANS CELL PRESENTATION OF TUMOR-ASSOCIATED ANTIGENS VIA IL-10 CONTENT

Exposure of mice to midrange UV radiation (UVB) (280-320 mm) in vivo l eads to suppression of the ability to induce delayed-type hypersensiti vity (DTH), Systemic administration of supernatants from UVB exposed k eratinocytes (KC) similarly inhibits the ability to induce DTH and the presence of interleukin-10 (IL-10) in the supernatants has been shown to be responsible for this effect. It has been hypothesized that rele ase of IL-10 by KC after exposure to UVB radiation in vivo may be resp onsible for UVB-induced inhibition of DTH and also for the inability o f chronically UVB-irradiated mice to immunologically reject immunogeni c UVB-induced skin tumors, To test directly whether supernatants from UVB-irradiated KC can inhibit presentation of tumor-associated antigen s (TAA) by epidermal Langerhans cells (LC), cultures of the transforme d murine KC line PAM 212 were exposed to 200 J/m(2) of UVB radiation a nd 24 h supernatants obtained, CAF(1) (H-2(a/d)) epidermal cells (EC) enriched for LC content were exposed to supernatants from irradiated ( UV-SN) or mock-irradiated (MI-SN) PAM 212 cells for 3 h followed by cu lture for 16 h in granulocyte-macrophage colony-stimulating factor and then were pulsed with soluble TAA derived from the murine spindle cel l tumor S1509a (H-2(a)). ECs were then washed and injected subcutaneou sly into naive CAF(1) mice three times at weekly intervals for priming , One week after the final immunization these mice were challenged sub cutaneously with live S1509(a) cells and tumor growth scored over time , Pretreatment of EC with UV-SN but not MI-SN inhibited the induction of effective immunity by this immunization scheme, ECs were also treat ed with UV-SN or MI-SN for 3 h then pulsed with TAA and injected into a hind footpad of previously immunized mice for elicitation of a DTH r esponse, Pretreatment of EC with UV-SN but not MI-SN inhibited the abi lity of EC to elicit DTH. Neutralization studies with specific neutral izing antibodies to IL-10 demonstrated that the presence of IL-10 in U V-SN was responsible for the inhibition of antigen presentation both f or induction and elicitation of immunity, UV-SN inhibits tumor antigen presentation by epidermal LC through the action of IL-10.