Figure 5.

Target cells loaded with secreted peptides from macrophages can activate antigen-specific CD8⁺ T cells. P815 mastocytoma was co-cultured with non-infected activated IC21 macrophages (P815 + Mφ) or Salmonella-infected IC21 macrophages (P815 + Inf Mφ). After 18 hr, P815 cells were harvested, labelled for 1 hr with ⁵¹Cr, and mixed with Salmonella-specific CTL. The source of CTL were spleen cells from Salmonella-infected BALB/c mice. The spleen cells were re-stimulated in vitro for 5 days with 100 µg/ml of Salmonella peptides generated by trypsin digestion before use in the CTL assay.