CD4 and precursor B-cell acute lymphoblastic leukemia: Further research has indicated that inhibiting myeloid–epithelial–reproductive tyrosine kinase (MERTK), a gene linked to the induction of an antiapoptotic gene expression signature in B-ALL cells, decreased PD-1 expression on both CD4+ and CD8+ T cells, leading to enhanced T cell activation and anti-ALL immune activity (78).