CD4 and neoplasm: Results showed that only the CD4−CD8− thymocytes had enhanced Sca1 expression at 14 days post tumor challenge (Supplementary Figure 7), but all four stages of thymocytes (CD4−CD8−, CD4+CD8+, CD4−CD8+, and CD4+CD8−) had drastically enhanced Sca1 expression at 21 days post challenge (Figure 8a).