FIGURE 3.

Presentation of tumor antigen by myeloid cells is necessary for tumor rejection by effector CD4 T cells. A, Schematic representation of the bone marrow chimera experiment. We made bone marrow chimeras in which the bone marrow–derived cells expressed the right (A^b, circles) or wrong (A^k, triangles) MHC class II allele to present the tumor antigen to Marilyn CD4 T cells. This was accomplished by using B10 (A^b) or B10.A (A^k) RAG.KO strain of mice. As additional control group, we also transferred A^b bone marrow into A^k mice (diamonds). Tumor-bearing mice were immunized with male A^b splenocytes to ensure efficient priming of the CD4 T cells. B, Survival of tumor-bearing mice was followed in the three different groups of chimera mice that either were left untreated or treated with Marilyn CD4 T cells, left and right panels, respectively.