CD4 and neoplasm: Because cells other than T cells can produce IFN-γ, and to determine if CD8+ T cells specifically had impaired cytokine production in CD4-cre x IKKβfl/fl tumor-bearing mice, CD8+ T cells were enriched from the spleen on day 7 post-tumor implantation using magnetic bead-based negative selection, and restimulated with irradiated tumor cells or PMA + ionomycin.