ZFP36 and thrombotic thrombocytopenic purpura: However, CD4+ T cells from CD4CreTTPf/f mice (Figure 2B) and from conventional TTP–/– mice (Supplementary Figure 2A) were more likely to become CD62L– CD44+ effector T cells compared with cells from WT mice, indicating that T cell-specific TTP deficiency leads to CD4 T-cell activation.