Parkinson's disease is a neurological disorder that leads to motor and cognitive disability.    Previous research has suggested that late-onset, sporadic Parkinson's disease arises from purely environmental causes, new data suggests the role of genetic susceptibility. Haydeh Payami, from the New York State Department of Health (New York, USA), and colleagues completed a genome-wide association study involving 2,000 Parkinson's disease patients, and have identified a genetic contributor that implicates the immune system. The team identified a gene, designated PARK18, found in the human leukocyte antigen (HLA) region -- which contains a large number of genes related to immune system function, that strongly associated with sporadic and late-onset cases of Parkinson's disease.  The researchers write that:  “The genetic association with [human leukocyte antigen] supports the involvement of the immune system in Parkinson's disease and offers new targets for drug development.”