CD33 and glioblastoma: Therefore, after conducting Mendelian Randomization analysis with glioblastoma as the exposure and the 21 target immune cell subtypes as outcomes, we identified only three cell subtypes with a unidirectional causal relationship with glioblastoma (CD45 on CD33+ HLA DR+ CD14dim, CD33+ HLA DR+ Absolute Count and IgD+ CD24+ B cell Absolute Count), and the OR measured by IVW method were OR = 1.307, CI = 1.072–1.595, P = 0.008 (Figures 3A, D), OR = 0.894, CI = 0.815–0.981, P = 0.018 (Figures 4A, D) and OR = 1.357, CI = 1.000–1.840, P = 0.049 (Figures 5A, D) respectively.