Conversely, the GvL reaction in allo-HSCT for CLL seems to be mainly mediated by T cells, as indicated by clinical studies showing that increased relapses were observed using T cell-depleting strategies [263,267] and that unrelated donor KIR genotype neither improves GvL reactions nor reduces the incidence of relapse in CLL [268,269]. Here, KIR3DL1 is linked to B-cell chronic lymphocytic leukemia.