CD4 and Huntington disease: Among HD patients, 28 (88%) had detectable SARS-CoV-2-S-reactive IFN-γ-producing CD8+ T cells (median, 0.10%; IQR 0.02–0.51%), 17 (53%) had detectable CD4+ T cells (median, 0.11%; IQR 0.05–0.22%), and in 17 (53%), both T-cell subsets were detectable at baseline.