Still, the detection of a significant increase in CD40 and ITGAM microglial markers in PD samples needs further investigation, as the highest concentration of microglia in the brain is located in the substantia nigra (Block et al., 2007), the first region affected by the loss of dopaminergic neurons in PD (Badger et al., 2014). This evidence concerns the gene ITGAM and Parkinson disease.