HLA-DRB1 and Alzheimer disease: In this VC cohort, four of the seven VC patients tested in the MHC blocking experiment (VC V, VC AA, VC AD and VC AF) HLA matched the available HLA class II Gag293-312 tetramer (DRB1*0701), and of these four patients only two (VC AA and VC AD) demonstrated blockable HLA class II-restricted CD8+ T cell activity (Fig. 2).