PEC fractions from tumor-bearing WT and p47phox−/−mice were co-cultured with anti-CD3/B7.1-stimulated CFSE-loaded splenocytes from non-tumor-bearing WT mice (E∶T ratio 1∶1), and CD4+ and CD8+ T cell proliferation was assessed by CFSE dye dilution. The gene discussed is CD80; the disease is neoplasm.