CD4 and hereditary spastic paraplegia: 57.1 ± 22.7 x 106/L (8.8 ± 3.9% of CD4+ T cells) in PD-dn patients, 56.9 ± 30.3 x 106/L (7.4 ± 2.5%) in PD-dt patients, and 89.3 ± 48.5 x 106/L (9.2 ± 4.1%) in HSP < 0.01 for absolute counts and P > 0.05 for % in PD-dn or PD-dt patients vs. HS