After adjusting for factors identified by univariate analysis that predicted mucositis (≥grade 3), infection before engraftment, and CMV reactivation, multivariate analyses revealed that the low proportion of CD3+CD4+CD161+ cells in peripheral blood was an independent predictor of mucositis (≥grade 3) (P = 0.020), infections before engraftment (P = 0.014), and CMV reactivation (P = 0.010). Here, KLRB1 is linked to mucositis.