Since ATL is a neoplasm of CD4+ T lymphocytes, and both CARD11(E626K) and HBZ were expressed in CD4+ T cells in our mice, we next evaluated the absolute numbers of CD4+ T cells and their subsets, namely CD4+CD44+CD62L− Tem and CD4+CD25+ Treg, together with CD8+ T cells, in the body of each mouse as the sum of their numbers in the whole bone marrow and whole spleen20,21 (Fig. 5, Supplementary Fig. 4). Here, CD44 is linked to neoplasm.