EPIDERMAL-CELL PRESENTATION OF TUMOR-ASSOCIATED ANTIGENS FOR INDUCTION OF TOLERANCE

Intravenous administration of hapten-coupled epidermal cells (EC) indu ces tolerance in mice. To assess the relevance of this observation to cutaneous tumors, the ability of EC to induce tolerance to the S1509a spindle cell tumor (H-2(a)) was examined. ECs were prepared from CAF(1 ) (H-2(a/d)) mice and the supernatant from a freeze-thaw lysate of S15 09a cells was used as a source of soluble tumor-associated Ag (TAA). E Cs were incubated in TAA or medium alone followed by washing. Two hund red thousand TAA-pulsed ECs, non-TAA-pulsed ECs, or TAA-pulsed ECs kil led by freeze-thawing were injected i.v. into groups of CAF(1) mice. T o determine whether this regimen induced tolerance, a tumor-specific d elayed-type hypersensitivity (DTH) response was measured in mice subse quently immunized to the S1509a tumor. To assess the degree of immunit y induced in these animals, ECs were prepared and deleted of Thy-1-bea ring cells by Ab and complement-mediated lysis. These cells were then pulsed with TAA and 5 x 10(5) were injected into the right hind footpa d of each mouse. Footpad swelling was assessed at 24 to 48 h as a meas ure of the DTH. Mice primed i.v. with viable TAA-pulsed EC but not kil led TAA-pulsed EC demonstrated a greatly suppressed DTH response. Othe r experiments demonstrated that exposure of EC to a dose of ultraviole t radiation (200 J/m(2)), which inhibits the ability of these cells to induce immunity by subcutaneous injection either before or after TAA pulsing, did not prevent induction of tolerance. Deletion of Ia-bearin g cells by Ab and complement-mediated lysis eliminated the ability of EC to induce tolerance, whereas deletion of Thy-1-bearing cells did no t. Separation of EC by density demonstrated that cells with a density greater than 1.077 were responsible for down-regulation of immunity in this system. An Ia(+), Thy-1(-), high density cell appears to mediate the induction of tolerance to the S1509a spindle cell tumor after i.v . administration of TAA-pulsed EC.