GZMB and Huntington disease: A more in-depth analysis of polyfunctionality revealed that among spike-specific (TNF+) CTL cells, the fraction of events that were double or triple positive for some markers, including IFNγ, CD107, IL-2, and/or GZMB, was similar to the HD group (Figure 3E; 1.8%, 2.0%, 0%, and 47% vs. 5.7%, 6.9%, 0%, and 33% median frequency values for IFNγ+ CD107a+, IL-2+, IL-2+ GZMB+, and GZMB+ populations in PWUD and HD, respectively), but other T-cell populations, such as IFNγ+ TNF+ CTL cells, appeared to be more frequent in HD (Figure 3E; 9.9% vs. 21% Mann–Whitney U test, ***p = 0.001).