They also proposed that HLA susceptibility to PD can be explained by a specific combination of amino acids at positions 70–74 on the HLA-DRB1 molecule referred to as the ‘shared epitope’ (SE) and that the SE in combination with valine at position 11 (11-V) is highly protective in PD, but a risk with the absence of 11-V. The gene discussed is HLA-DRB1; the disease is Parkinson disease.