SNCA and multiple system atrophy: In the simultaneous presence of increasing concentrations of free β- and γ-synuclein monomers prior to measurement of free antibody titre on plates coated with α-synuclein monomer (Fig. 10c) plasma samples from normal individuals still supported a two-affinity state model but to a lower extend than in the previous set-ups, whereas plasma samples from PD and MSA patients required high β−/γ-synuclein concentrations for maximum of inhibition.