Figure 3.

Lack of mutual competition between peptide and lipid antigens. (A) A lipid antigen does not compete for peptide recognition. A20/CD1.1 transfectants were pulsed with either 5.5 μM p99, 5.5 μM p99A1, or 25 μM α-GalCer and then were pulsed either with 1 μM Ova or 1.25 μM p18 peptide. After washing out the antigen, APC were irradiated and cultured with in vitro activated T cells, and cytokine detection assays were carried out as described above. The production of IFN-γ from untransfected cells pulsed with Ova, or T cells alone, was <8 units/ml. Representative data are from one of three experiments. (B) Peptide antigens do not compete for lipid recognition. A20/CD1.1 cells were pulsed either with 10 μM p99, 10 μM p18, or 1 μM Ova; they then were pulsed further with 0.1 μM α-GalCer and were handled as described in A. These APC then were cultured together with spleen cells from CB6F1 mice. After 3 days of coculture, ELISAs for IFN-γ detection were carried out.