Cell-mediated immune response to syngeneic UV-induced tumors. IV. The presence of I-A and I-E subregion-coded antigens on the accessory cell required for the in vitro differentiation of cytotoxic T lymphocytes

Both I-A and I-E subregion-coded antigens were shown to be present on the accessory cell required for a tumor immune response in vitro. Draining lymph node (DLN) cells from mice immunized in the hind footpad with tumor cells proliferate and differentiate into cytotoxic T lymphocytes (CTL) after 4 days in vitro. Both proliferation and differentiation of CTL activity in vitro require the presence of an adherent, radioresistant, Thy-1 negative and Ia-positive accessory cell. The pretreatment of DLN cells with anti-Iak antisera + C caused a marked reduction in accessory cell function that was restored upon addition of 1000 rad irradiated DLN or spleen cells. Absorption experiments demonstrated that removal of both I-A and I-E subregion specificities from anti-Iak antisera was necessary to deplete the antisera of cytotoxic activity against DLN accessory cells. Antisera specific for the A, B, and J subregions as well as antisera specific for the J, E subregions or E, C subregions were also effective at removing accessory cell activity from DNL cells. One of these antisera possessed activity against only specificity Ia.7 of the Ek haplotype, suggesting the expression of Ia.7 on the accessory cell. Antigens coding in the I-J subregion could not be detected when an antiserum with known anti-suppressor cell activity was used. These results suggest the expression of I-A and I-E subregion-coded antigens on the accessory cell, and data are presented indicating that both antigens are expressed on the same cell.